how good are class D amplifiers?
 

"Rob" wrote in message
...
Serge Auckland wrote:
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote


I own a Marantz Model 18 Receiver, dating from 1968. It originally
cost US$1,200.00 and was the most power receiver on the planet, back
then. For it's time, it was quite a sophisticated product, employing
full complementary silicon outputs, relay protection system and
other nifty stuff. It was critically appraised by reviewers at the
time and when I purchased mine (ca: 1977) I was stunned at how much
better it sounded than many contemporary amplifiers of similar (60
Watts) or even more power. Just for yuks, I recently compared it to
a more modern Marantz amplifier (cost around AUS$1,000.00). No
comparison. The modern amp was somewhat better sounding. And,
allowing for inflation, the modern amp was MUCH less expensive.
Don't even get me started on loudspeakers. The technology for
designing speakers has improved in leaps and bounds over the last 40
years.


S'funny, we keep getting told how 'good amps' don't have a
sound....???
**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.

Therefore no amplifier has no 'sound' of its own then?
**Nope. That's not what I said.


--
Trevor Wilson
www.rageaudio.com.au

The *ideal* amplifier has no sound of its own, and no amplifier is ideal.
However, for many years now, amplifiers come awfully close to the ideal,
and consequently, except for the nittiest of nit-pickers, I subscribe to
the view that no (half-decent) amplifier has a sound of its own, and
consequently all sound the same.

Certain conditions apply, like operation below clipping into loads for
which the amplifier was designed, using music signals.

S.

I simply don't get this. I've been using 5 SS amps of late (Quad 405, Rose
power amp, Cambridge AV, Behringer A500, and that within a Pure mini
system), as well as others on and off over the years, and I feel each has
'a sound of its own'.

But this has been done-to-death in this NG. One thing I was never clear on
is the definition of 'half-decent'. One definition (Stewart Pinkerton
IIRC) was double power into half impedance, down to 2 Ohms (50/8; 100/4,
200/2 or something, plus some other stuff), but I've never seen a sensible
money amp that could come close.

Could you name the cheapest available new amplifier that sounds the same
as (say) your own at medium-high volume?

Just curious!

Rob

Price of the amplifier isn't important. It is well recognised, at least
amongst audio professionals, that the ear's ability to hear differences has
a lower threshold. If an amplifier's performance is below that threshold,
then all differences between such amplifiers is not audible.

Here is my understanding of the threshold levels:-

Distortions - all types, THD, IMD 0.1%
Important Note: This distortion is measured from 20Hz to 20kHz with a
bandwidth of 100kHz, and must be maesured into the loads declared suitable
by the designer. For example, the QUAD 405 is rated at 100watts into any
load 4-8 ohms. Consequently, I would expect it to work with loudspeakers
rated at 6 ohms upwards. Note that 4 ohm rated loudspeakers can drop to 3.2
ohms, and would consequently fall outside QUAD's specification for the 405.

Frequency response +-1dB 20Hz-20kHz
Important note: This frequency response is measured across the loudspeaker
load, *not* across a dummy load. This requires the amplifier to have a low
output impdeance as otherwise, the loudspeaker's impedance characteristic
will modify the frequency response.

Hum and noise 80dB measured on a bandwidth of 20Hz-20kHz, and no worse
than -60dB outside that band. It is important that the amplifier have no
instabilities at sub or supersonic frequencies.

Crosstalk: 60dB
In practice, crosstalk below -40dB is unlikely to be audible under programme
conditions. It is important that the distortion of the crosstalk be below
0.1% as otherwise, the crosstalk distortion could swamp the speaking
channel's distortion. This is a rare condition, but not unknown with poor
designs with poor power-supply rejection.


If two amplifiers, whether SS or valved meet the above criteria, then their
sound will be indistinguishable.

As to what amplifiers meet these criteria, these days almost any modern
Solid State amplifier will do. SOme valve amplifiers will too, espcially if
they are Push-Pull Ultra-Linear with overall negative feedback. SET will
almost certainly *not* meet these criteria as their distortion is too high,
and their output impedance too high resulting in gross frequency response
errors.

Amplifiers *will* sound different if they are not gain-matched to better
than 0.5dB, ideally 0.1dB as the louder one will normally sound "better".
Also, if one or both amplifiers being compared are allowed to go into
overload, then what you will be hearing is their overload behaviour, which
could well be very different.

Finally, any sighted test will inevitably have the possibility of bias,
however inadvertent, so comparisons should be done blind, ideally
double-blind.

If you take two amplifiers and compare them properly, even two very
different amplifiers, provided they each meet the minimum audibility
criteria, and both are used within their output capacity such that neither
clips, they *will* sound the same.

S.

how good are class D amplifiers?
 

On 2007-05-20, Keith G wrote:

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote
Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.

It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

Logic error, Keith. You can only conclde "no amplifier has no sound
of its own" (i.e. every amplfier has a sound of its own) from three
conditons:

- The ideal amplifier has no sound of its own

- No amplifier is ideal

- All non-idealities in an amplifier create a sound.

You cannot (logically) conclude anything about the sound (or not) of
the non-ideal amplifier from the first two conditions.

The third condition has not been postulated (IIRC). Indeed it isn't true.
There are thresholds for the audibility of non-idealities.

--
John Phillips

how good are class D amplifiers?
 

On 2007-05-17, Jim Lesurf wrote:
In article , John Phillips
wrote:
In deciding how much power to deploy, one of the interesting questions
that has proved difficult to answer definitively is "how loud is an
orchestra" (when you are in good seats not too far from the stage).

For me, the real questions here aren't so much with measuring the sound
level you'd get in such a seat. They are in translating that into what is
required at home in a domestic room.

There are various problems with this translation. ...
snip

My own experience is that the sound pressure levels required for a
convincing result at home are often far lower than those reported as being
present in the hall.

Yes, but the original level places an upper bound (or so I assume, in
accordance with your experience). Given the problems with the rest of the
translation (some of which you enumerate) it's a useful starting point.

For the above reasons I am quite doubtful of the claims made by Mobile
Fidelity that you need high power amps even with low efficiency speakers.
Although this will all depend a lot on the details of the listening room,
etc, etc.

I think these are the recent Musical Fidelity advertisements. If so
I agree. They set too high a target at 112 dBA (1 metre) and the 7 dB
loss they assume at 10 feet is too high for a realistic listening room.
Their figures come in at 3 dB above even my conservative targets.
Of course that suits their product range.

--
John Phillips

how good are class D amplifiers?
 

Serge Auckland wrote:
"Rob" wrote in message
...
Serge Auckland wrote:
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote


I own a Marantz Model 18 Receiver, dating from 1968. It originally
cost US$1,200.00 and was the most power receiver on the planet, back
then. For it's time, it was quite a sophisticated product, employing
full complementary silicon outputs, relay protection system and
other nifty stuff. It was critically appraised by reviewers at the
time and when I purchased mine (ca: 1977) I was stunned at how much
better it sounded than many contemporary amplifiers of similar (60
Watts) or even more power. Just for yuks, I recently compared it to
a more modern Marantz amplifier (cost around AUS$1,000.00). No
comparison. The modern amp was somewhat better sounding. And,
allowing for inflation, the modern amp was MUCH less expensive.
Don't even get me started on loudspeakers. The technology for
designing speakers has improved in leaps and bounds over the last 40
years.

S'funny, we keep getting told how 'good amps' don't have a
sound....???
**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.
Therefore no amplifier has no 'sound' of its own then?
**Nope. That's not what I said.


--
Trevor Wilson
www.rageaudio.com.au

The *ideal* amplifier has no sound of its own, and no amplifier is ideal.
However, for many years now, amplifiers come awfully close to the ideal,
and consequently, except for the nittiest of nit-pickers, I subscribe to
the view that no (half-decent) amplifier has a sound of its own, and
consequently all sound the same.

Certain conditions apply, like operation below clipping into loads for
which the amplifier was designed, using music signals.

S.
I simply don't get this. I've been using 5 SS amps of late (Quad 405, Rose
power amp, Cambridge AV, Behringer A500, and that within a Pure mini
system), as well as others on and off over the years, and I feel each has
'a sound of its own'.

But this has been done-to-death in this NG. One thing I was never clear on
is the definition of 'half-decent'. One definition (Stewart Pinkerton
IIRC) was double power into half impedance, down to 2 Ohms (50/8; 100/4,
200/2 or something, plus some other stuff), but I've never seen a sensible
money amp that could come close.

Could you name the cheapest available new amplifier that sounds the same
as (say) your own at medium-high volume?

Just curious!

Rob

Price of the amplifier isn't important. It is well recognised, at least
amongst audio professionals, that the ear's ability to hear differences has
a lower threshold. If an amplifier's performance is below that threshold,
then all differences between such amplifiers is not audible.

Here is my understanding of the threshold levels:-

Distortions - all types, THD, IMD 0.1%
Important Note: This distortion is measured from 20Hz to 20kHz with a
bandwidth of 100kHz, and must be maesured into the loads declared suitable
by the designer. For example, the QUAD 405 is rated at 100watts into any
load 4-8 ohms. Consequently, I would expect it to work with loudspeakers
rated at 6 ohms upwards. Note that 4 ohm rated loudspeakers can drop to 3.2
ohms, and would consequently fall outside QUAD's specification for the 405.

Frequency response +-1dB 20Hz-20kHz
Important note: This frequency response is measured across the loudspeaker
load, *not* across a dummy load. This requires the amplifier to have a low
output impdeance as otherwise, the loudspeaker's impedance characteristic
will modify the frequency response.

Hum and noise 80dB measured on a bandwidth of 20Hz-20kHz, and no worse
than -60dB outside that band. It is important that the amplifier have no
instabilities at sub or supersonic frequencies.

Crosstalk: 60dB
In practice, crosstalk below -40dB is unlikely to be audible under programme
conditions. It is important that the distortion of the crosstalk be below
0.1% as otherwise, the crosstalk distortion could swamp the speaking
channel's distortion. This is a rare condition, but not unknown with poor
designs with poor power-supply rejection.


If two amplifiers, whether SS or valved meet the above criteria, then their
sound will be indistinguishable.


Many thanks - copied to file for future reference! I'm still confused
by 'power'. This is presumably covered to a point with your distortion
criterion, but I remain to be convinced that most amplifiers are by any
means linear as the volume goes up.


As to what amplifiers meet these criteria, these days almost any modern
Solid State amplifier will do. SOme valve amplifiers will too, espcially if
they are Push-Pull Ultra-Linear with overall negative feedback. SET will
almost certainly *not* meet these criteria as their distortion is too high,
and their output impedance too high resulting in gross frequency response
errors.


OK - and I'm sure you could see this coming (!) - why did you (and many
others on this NG) spend so many thousands on amplifiers when you could
have a same-sounding result for a few hundred?

Amplifiers *will* sound different if they are not gain-matched to better
than 0.5dB, ideally 0.1dB as the louder one will normally sound "better".
Also, if one or both amplifiers being compared are allowed to go into
overload, then what you will be hearing is their overload behaviour, which
could well be very different.

Finally, any sighted test will inevitably have the possibility of bias,
however inadvertent, so comparisons should be done blind, ideally
double-blind.

If you take two amplifiers and compare them properly, even two very
different amplifiers, provided they each meet the minimum audibility
criteria, and both are used within their output capacity such that neither
clips, they *will* sound the same.


Yes, I agree, and a little more time and effort on my part might make me
think again. If only I wasn't so damned sure ;-)

how good are class D amplifiers?
 

"Rob" wrote in message
...
Serge Auckland wrote:
"Rob" wrote in message
...
Serge Auckland wrote:
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote in message
...
"Trevor Wilson" wrote


I own a Marantz Model 18 Receiver, dating from 1968. It originally
cost US$1,200.00 and was the most power receiver on the planet,
back then. For it's time, it was quite a sophisticated product,
employing full complementary silicon outputs, relay protection
system and other nifty stuff. It was critically appraised by
reviewers at the time and when I purchased mine (ca: 1977) I was
stunned at how much better it sounded than many contemporary
amplifiers of similar (60 Watts) or even more power. Just for
yuks, I recently compared it to a more modern Marantz amplifier
(cost around AUS$1,000.00). No comparison. The modern amp was
somewhat better sounding. And, allowing for inflation, the modern
amp was MUCH less expensive. Don't even get me started on
loudspeakers. The technology for designing speakers has improved
in leaps and bounds over the last 40 years.

S'funny, we keep getting told how 'good amps' don't have a
sound....???
**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.
Therefore no amplifier has no 'sound' of its own then?
**Nope. That's not what I said.


--
Trevor Wilson
www.rageaudio.com.au

The *ideal* amplifier has no sound of its own, and no amplifier is
ideal. However, for many years now, amplifiers come awfully close to
the ideal, and consequently, except for the nittiest of nit-pickers, I
subscribe to the view that no (half-decent) amplifier has a sound of
its own, and consequently all sound the same.

Certain conditions apply, like operation below clipping into loads for
which the amplifier was designed, using music signals.

S.
I simply don't get this. I've been using 5 SS amps of late (Quad 405,
Rose power amp, Cambridge AV, Behringer A500, and that within a Pure
mini system), as well as others on and off over the years, and I feel
each has 'a sound of its own'.

But this has been done-to-death in this NG. One thing I was never clear
on is the definition of 'half-decent'. One definition (Stewart Pinkerton
IIRC) was double power into half impedance, down to 2 Ohms (50/8; 100/4,
200/2 or something, plus some other stuff), but I've never seen a
sensible money amp that could come close.

Could you name the cheapest available new amplifier that sounds the same
as (say) your own at medium-high volume?

Just curious!

Rob

Price of the amplifier isn't important. It is well recognised, at least
amongst audio professionals, that the ear's ability to hear differences
has a lower threshold. If an amplifier's performance is below that
threshold, then all differences between such amplifiers is not audible.

Here is my understanding of the threshold levels:-

Distortions - all types, THD, IMD 0.1%
Important Note: This distortion is measured from 20Hz to 20kHz with a
bandwidth of 100kHz, and must be maesured into the loads declared
suitable by the designer. For example, the QUAD 405 is rated at 100watts
into any load 4-8 ohms. Consequently, I would expect it to work with
loudspeakers rated at 6 ohms upwards. Note that 4 ohm rated loudspeakers
can drop to 3.2 ohms, and would consequently fall outside QUAD's
specification for the 405.

Frequency response +-1dB 20Hz-20kHz
Important note: This frequency response is measured across the
loudspeaker load, *not* across a dummy load. This requires the amplifier
to have a low output impdeance as otherwise, the loudspeaker's impedance
characteristic will modify the frequency response.

Hum and noise 80dB measured on a bandwidth of 20Hz-20kHz, and no worse
than -60dB outside that band. It is important that the amplifier have no
instabilities at sub or supersonic frequencies.

Crosstalk: 60dB
In practice, crosstalk below -40dB is unlikely to be audible under
programme conditions. It is important that the distortion of the
crosstalk be below 0.1% as otherwise, the crosstalk distortion could
swamp the speaking channel's distortion. This is a rare condition, but
not unknown with poor designs with poor power-supply rejection.


If two amplifiers, whether SS or valved meet the above criteria, then
their sound will be indistinguishable.


Many thanks - copied to file for future reference! I'm still confused by
'power'. This is presumably covered to a point with your distortion
criterion, but I remain to be convinced that most amplifiers are by any
means linear as the volume goes up.

How can they not be? Non-linearity causes amongst other things harmonic
distortion, so provided the THD is below 0.1%, then the linearity is
similarly assured. However, increasing the volume will cause increasing
distortion in the loudspeakers. Their distortion figures are magnitudes
greater than amplifiers. However, a loudspeaker's distortion will be
substantially the same whatever amplifier is driving it, (I'm trying to
think of a mechanism that could change that statement, but can't) so as the
volume goes up, your comparison between amplifiers would still be valid.
If when playing music loud, one amplifier is clearly different from another,
then I would bet you a pound to the proverbial pinch of snuff that one (or
both) amps are clipping, and what you are hearing is the different behavior
on overload. For example, a transistor amplifier will clip hard when the
output voltage is hitting the rails. Valve amplifiers tend to overload much
more gracefully, in fact, with most valve amplifiers, they are rated not at
clipping point as are transistor amps, but at a certain THD level, say 1% or
5% or whatever.

An interesting aside is that two transistor amplifiers of equal continuous
power ratings, but one with a stabilised supply and the other with a
conventional "sagging" supply will sound different at high levels: The amp
with the stabilised supply will hit the rails and that's it, it will clip
thereafter. I doesn't have any more power under dynamic conditions than it
has under continuous sine-waves. An amplifier with a sagging supply will
provide more power under dynamic (i.e music) conditions than it does on
sine-wave duty, and consequently, if you are evaluating the two amplifiers
without test instrumentation, just by ears, it is very easy to conclude that
the less sophisticated amp sounds better. In fact, if you monitor the output
level of both amps, and ensure that neither goes outside it's continuous
power rating, then they will sound identical, all other things being equal.




As to what amplifiers meet these criteria, these days almost any modern
Solid State amplifier will do. SOme valve amplifiers will too, espcially
if they are Push-Pull Ultra-Linear with overall negative feedback. SET
will almost certainly *not* meet these criteria as their distortion is
too high, and their output impedance too high resulting in gross
frequency response errors.


OK - and I'm sure you could see this coming (!) - why did you (and many
others on this NG) spend so many thousands on amplifiers when you could
have a same-sounding result for a few hundred?

I didn't! I use active 'speakers with the amplifiers built-in. But that
apart, I don't know why people spend many thousands on amplifiers when
indeed, they would have the same sounding result for a few hundred. I
suppose it's for the same reasons that people will spend money on expensive
mechanical watches, when a £ 5.00 digital watch from a market stall will
actually keep better time, or why people spend lots of money on jewelry when
fakes are indistinguishable except to an expert using an eyeglass. What I am
saying here is that the purchase of Hi-Fi equipment is not a rational
purchase, and the ownership of fine hi-fi equipment gives us an emotional
feeling that has nothing to do with the ostensive "purpose" of the
equipment. I am not immune from this myself. I own a pair of Broadcast
turntables that I am inordinately fond of. I *really* enjoy using them, and
the pride of ownership comes from their extraordinary build quality, as well
as audio quality, which I will say, however, is probably no better that
something much more "ordinary"

Amplifiers *will* sound different if they are not gain-matched to better
than 0.5dB, ideally 0.1dB as the louder one will normally sound "better".
Also, if one or both amplifiers being compared are allowed to go into
overload, then what you will be hearing is their overload behaviour,
which could well be very different.

Finally, any sighted test will inevitably have the possibility of bias,
however inadvertent, so comparisons should be done blind, ideally
double-blind.

If you take two amplifiers and compare them properly, even two very
different amplifiers, provided they each meet the minimum audibility
criteria, and both are used within their output capacity such that
neither clips, they *will* sound the same.


Yes, I agree, and a little more time and effort on my part might make me
think again. If only I wasn't so damned sure ;-)

If I have put a little doubt into this surety, it will have been worth while
:-)

S.

how good are class D amplifiers?
 

In article , Dave Plowman (News)
writes
In article ,
tony sayer wrote:
Remember these generally aren't the same as domestic BC1s. Depending on
age they may only have an HF 1300 and not the additional HF 2000?
'super tweeter'. The amp is also of rather lower power than most would
use. Again maybe only early ones had a mid range 'suck out' so beloved
of BBC designs of the day. In a nutshell, sound rather different from
the contemporary domestic version.

Well What was good for the BBC in the good old days was good enough for
most all audiophiles;)

Not really true. What is pragmatic for broadcast use may well be bettered
at home.

I'll give just one example. When your favourite FM service started in the
'50s, some listeners complained of HF 'artifacts'. None of which were
'agreed' by the duty engineer. The answer was simple. The standard
monitoring speaker in use then - the LSU10, with a Parmeko dual concentric
driver, didn't reproduce much above 10 kHz. Or 10,000 cycles per second as
it was then. ;-) Auxiliary tweeters were bought from a retail components
shop (rather like Maplin used to be) and hastily bolted to the grills.

Humm.. The 50's eh?..


--
Tony Sayer

how good are class D amplifiers?
 

"John Phillips" wrote in message
...
On 2007-05-20, Keith G wrote:

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote
Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.

It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

Logic error, Keith. You can only conclde "no amplifier has no sound
of its own" (i.e. every amplfier has a sound of its own) from three
conditons:

- The ideal amplifier has no sound of its own

- No amplifier is ideal

- All non-idealities in an amplifier create a sound.

You cannot (logically) conclude anything about the sound (or not) of
the non-ideal amplifier from the first two conditions.

The third condition has not been postulated (IIRC). Indeed it isn't
true.



No, your third condition is an 'introduced' red herring - the inference
that I suggest may be drawn from Trevor's statements is, I think, an
admissible product of simple deductive reasoning in the modus ponendo
ponens form provided by those statements....

(ie. it works for me....!! ;-)

how good are class D amplifiers?
 

"Keith G" wrote in message
...

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote


S'funny, we keep getting told how 'good amps' don't have a
sound....???

**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.


Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.



It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

**You have failed Logic 101.

--
Trevor Wilson
www.rageaudio.com.au




--
Posted via a free Usenet account from http://www.teranews.com

how good are class D amplifiers?
 

In article , Keith G
wrote:

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote


S'funny, we keep getting told how 'good amps' don't have a
sound....???

**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.


Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.



It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

I can suggest at least two "conclusions" which fit with what Trevor said.

1) That "ideal" is defined in this context to mean what he wrote. i.e. that
an ideal amp would/will have no "sound".

2) That this isn't a matter of a false dichtomy. i.e. *some* amps might
have no "sound". Not a matter of all or none.

In the above respect I have my doubt about the way people are trying to use
both terms, "ideal" and "sound".

So far as I know there have been various controlled tests where no-one
listening was able to distinguish one of the amps under comparison from
another. Also tests where no-one was able to distinguish the amp followed
by a resistive attenuator from a wire bypass. Thus I doubt it is the case
that no amp is "ideal" in the terms Trevor used.

The reason such tests have been rare in audio mags in recent years may be
that the reviewers got fed up with tests whose results indicated that they
could not find reliable evidence to support their belief that they could
hear differences, plus that doing such a test requires more time, care, and
understanding than they could be bothered to apply. :-)

Also, the "sound" produced by the amp is as a result of feeding it with an
imput signal and playing its output via a speaker. This definition means it
is a result of how it may (or may not) alter the signal in a way that has
an audible effect. That means the "sound" depends on both the signal used
and the loudspeakers, and is based upon any signal alterations made by the
amp in that use.

Of course, the amp may be adding audible noise/hum and making mechanical
buzzing noises which might be a "sound" of its own. Otherwise any "sound"
will be based on it altering the signal so that the output isn't simply a
scaled version of the input, and the changes are large enough to be
audible.

Personally, what I've found interesting over the years is just how large
the changes in signal waveforms can be in some situations without people
actually noticing, yet people say they can hear things when tests relying
on sound alone fail to support their claim.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

how good are class D amplifiers?
 

In article , Rob
wrote:

I simply don't get this. I've been using 5 SS amps of late (Quad 405,
Rose power amp, Cambridge AV, Behringer A500, and that within a Pure
mini system), as well as others on and off over the years, and I feel
each has 'a sound of its own'.

The problems with the above are as follows:

1) Many people have formed such views as a result of simply using various
amps. I've also repeatedly changed from one amp to another and thought it
made a difference. But then later on I changed my mind when I listened
again. The problem here is partly one of control - e.g. not level matching
- and partly that human hearing varies with time, etc. So each time you
listen your ears/brain may simply respond slightly differently.

2) Yet when people do level-matched comparisons and avoid obvious snags
like clipping *and* have only the sound to rely upon, the result is often
that they can't reliably tell one amp from another.

FWIW A number of tests have also shown that people tend to hear
'differences' even when the same system is used in the same way.

The above does not mean that all amps produce the same results. Nor does it
mean that they all produce different results. But it means that people form
views that may simply be mistaken, and often fail to do comparisons which
help prevent well-known mistakes from occurring.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

how good are class D amplifiers?
 

In article , Serge Auckland
wrote:

"Rob" wrote in message
...


Many thanks - copied to file for future reference! I'm still confused
by 'power'. This is presumably covered to a point with your
distortion criterion, but I remain to be convinced that most
amplifiers are by any means linear as the volume goes up.

How can they not be? Non-linearity causes amongst other things harmonic
distortion, so provided the THD is below 0.1%, then the linearity is
similarly assured.

I am slightly wary of the above statement. If you are using THD as a guide
I'd prefer to explicitly extend it over a range of frequencies and powers
*and* to various types of load. The reason being various types of 'dynamic'
nonlinearity which the figures might otherwise miss.

I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at harmonics of
the test frequency in most cases. I've seen amps where the THD value was
low, but where there was much more LF garbage due to this.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

how good are class D amplifiers?
 

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote in message
...

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote


S'funny, we keep getting told how 'good amps' don't have a
sound....???

**Because that is a fact. The ideal amplifier has no 'sound' of
it's
own. No amplifier is ideal.


Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.



It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

**You have failed Logic 101.


Good. You, OTOH, have failed to spot that your argument is a simple
categorical syllogism along these lines:

Red apples taste sweet.
There are no red apples.
Therefore there are no sweet apples.

(Where 'red apples' = 'ideal amps' and 'sweet' = 'no sound', in this
example...)

Easy, innit? :-)

As to whether lack of sweetness is undesirable (or inaudible) is a
matter for the individual...

Now, forget all that (it'll come, one day) tell me if you have had any
'hands on' with the Technics 3000 series SS pre/power combo?

It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on
the Fidelios and got a much better, more *exciting* (more listenable)
sound. As the SET (according to the pundits here) produces enough
distortion to bend light and the Fidelios have little or nothing outside
the range of the human voice, I am intrigued as to what's going on?

Is it me?

(Note that both systems share all sources and exist side by side here -
I'm not concerned about *winners*....)

how good are class D amplifiers?
 

Keith G wrote:


Now, forget all that (it'll come, one day) tell me if you have had any
'hands on' with the Technics 3000 series SS pre/power combo?

It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on
the Fidelios and got a much better, more *exciting* (more listenable)
sound.

Of course it did as it was full of lovely ear pleasing second harmonic
distortion. Psycho-acoustics in action.

Ian

how good are class D amplifiers?
 

"Keith G" wrote in message
...

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote in message
...

"Trevor Wilson" wrote in message
.. .

"Keith G" wrote


S'funny, we keep getting told how 'good amps' don't have a
sound....???

**Because that is a fact. The ideal amplifier has no 'sound' of it's
own. No amplifier is ideal.


Therefore no amplifier has no 'sound' of its own then?

**Nope. That's not what I said.



It's what it looks like to me - your words (as above): "The ideal
amplifier has no 'sound' of it's own. No amplifier is ideal." - what
conclusion could be possibly drawn from that statement other than all
amplifiers are not ideal and therefore have a 'sound'...??

**You have failed Logic 101.


Good. You, OTOH, have failed to spot that your argument is a simple
categorical syllogism along these lines:

Red apples taste sweet.
There are no red apples.
Therefore there are no sweet apples.

(Where 'red apples' = 'ideal amps' and 'sweet' = 'no sound', in this
example...)

Easy, innit? :-)

As to whether lack of sweetness is undesirable (or inaudible) is a matter
for the individual...

Now, forget all that (it'll come, one day) tell me if you have had any
'hands on' with the Technics 3000 series SS pre/power combo?

It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on the
Fidelios and got a much better, more *exciting* (more listenable) sound.
As the SET (according to the pundits here) produces enough distortion to
bend light and the Fidelios have little or nothing outside the range of
the human voice, I am intrigued as to what's going on?

Is it me?

(Note that both systems share all sources and exist side by side here -
I'm not concerned about *winners*....)


It most likely *is* you, or at least, your preferences. Whilst it may be an
exaggeration (slight?) to say your Fidelios have nothing outside voice
range, or that your SETs have enough distortion to bend light, but
nevertheless, what I think is happening is that you find the more exciting
sound more to your liking.

S.

how good are class D amplifiers?
 

"Ian Bell" wrote in message
...
Keith G wrote:


Now, forget all that (it'll come, one day) tell me if you have had
any
'hands on' with the Technics 3000 series SS pre/power combo?

It is reputed to have some of the lowest noise and distortion figures
on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET
on
the Fidelios and got a much better, more *exciting* (more listenable)
sound.

Of course it did as it was full of lovely ear pleasing second harmonic
distortion. Psycho-acoustics in action.



Lovely.

Makes me wonder why no-one has ever built an amp with a common pre
section driving two power sections - one SS, one triode - switchable via
a toggle switch with 'Excitement' and 'Accurate' labelling...??

:-)

how good are class D amplifiers?
 

"Serge Auckland" wrote in message
...

"Keith G" wrote


Now, forget all that (it'll come, one day) tell me if you have had
any 'hands on' with the Technics 3000 series SS pre/power combo?

It is reputed to have some of the lowest noise and distortion figures
on record


Make that 'sets of'....


(Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET
on the Fidelios and got a much better, more *exciting* (more
listenable) sound. As the SET (according to the pundits here)
produces enough distortion to bend light and the Fidelios have little
or nothing outside the range of the human voice, I am intrigued as to
what's going on?

Is it me?

(Note that both systems share all sources and exist side by side
here - I'm not concerned about *winners*....)


It most likely *is* you, or at least, your preferences. Whilst it may
be an exaggeration (slight?) to say your Fidelios have nothing outside
voice range, or that your SETs have enough distortion to bend light,
but nevertheless, what I think is happening is that you find the more
exciting sound more to your liking.


:-)

See my reply to Iain!!

(For radio voices - reverse all the above, however....)

how good are class D amplifiers?
 

In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on
the Fidelios and got a much better, more *exciting* (more listenable)
sound. As the SET (according to the pundits here) produces enough
distortion to bend light and the Fidelios have little or nothing outside
the range of the human voice, I am intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up on the their telly
for that 'technicolor' look. So actually preferring some types of
distortion doesn't seem that unusual to me. That's why so many like vinyl,
after all.

--
*Sleep with a photographer and watch things develop

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

In article ,
Keith G wrote:
See my reply to Iain!!

Is he around again? Not got his post here.

--
*I see you've set aside this special time to humiliate yourself in public

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

"Ian Bell" wrote in message

Keith G wrote:


Now, forget all that (it'll come, one day) tell me if
you have had any 'hands on' with the Technics 3000
series SS pre/power combo?

It is reputed to have some of the lowest noise and
distortion figures on record (Martin Colloms) yet, last
night when I was listening to a particularly fine 1958
recording of Grieg's Concerto in A minor (Solomon), I
switched from the Technics on the TLS80s to my 2A3 SET
on the Fidelios and got a much better, more *exciting*
(more listenable) sound.

Of course it did as it was full of lovely ear pleasing
second harmonic distortion. Psycho-acoustics in action.

Please explain to me how one can play music through a nonlinear system that
has second harmonic distoriton without the attendant IM distortion.

how good are class D amplifiers?
 

Dave Plowman (News) wrote:
In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on
the Fidelios and got a much better, more *exciting* (more listenable)
sound. As the SET (according to the pundits here) produces enough
distortion to bend light and the Fidelios have little or nothing outside
the range of the human voice, I am intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up on the their telly
for that 'technicolor' look. So actually preferring some types of
distortion doesn't seem that unusual to me. That's why so many like vinyl,
after all.


It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction produce a more
satisfying result. A painter's rendition, a musician's performance, a
poet's meter, a writer's (etc). These examples may result in a more
satisfying, more *realistic*, experience of the original event, despite
the fact their efforts are not technically facsimiles.

Is distortion always bad?

how good are class D amplifiers?
 

"Rob" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and distortion
figures on record (Martin Colloms) yet, last night when I was
listening to a particularly fine 1958 recording of Grieg's Concerto
in A minor (Solomon), I switched from the Technics on the TLS80s to
my 2A3 SET on the Fidelios and got a much better, more *exciting*
(more listenable) sound. As the SET (according to the pundits here)
produces enough distortion to bend light and the Fidelios have
little or nothing outside the range of the human voice, I am
intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up on the their
telly
for that 'technicolor' look. So actually preferring some types of
distortion doesn't seem that unusual to me. That's why so many like
vinyl,
after all.


It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction produce a more
satisfying result. A painter's rendition, a musician's performance, a
poet's meter, a writer's (etc). These examples may result in a more
satisfying, more *realistic*, experience of the original event,
despite the fact their efforts are not technically facsimiles.

Is distortion always bad?


The instant you touch a volume control you distort the sound to suit
your needs....

how good are class D amplifiers?
 

"Rob" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and distortion figures on
record (Martin Colloms) yet, last night when I was listening to a
particularly fine 1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s to my 2A3 SET on
the Fidelios and got a much better, more *exciting* (more listenable)
sound. As the SET (according to the pundits here) produces enough
distortion to bend light and the Fidelios have little or nothing outside
the range of the human voice, I am intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up on the their
telly
for that 'technicolor' look. So actually preferring some types of
distortion doesn't seem that unusual to me. That's why so many like
vinyl,
after all.


It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction produce a more
satisfying result. A painter's rendition, a musician's performance, a
poet's meter, a writer's (etc). These examples may result in a more
satisfying, more *realistic*, experience of the original event, despite
the fact their efforts are not technically facsimiles.

Is distortion always bad?

Is distortion always bad? Now there's an interesting question.

For me yes, High Fidelity sound reproduction for me has been constant battle
to identify forms of distortion and eliminate them. When I first started in
Hi-Fi, few amplifiers were "transparent", and bit by bit they improved such
that by the mid '80s, no further subjective improvement became possible.
Amplifiers since have become relative cheaper, more reliable and higher
powered, but performance hasn't improved, in fact can't improve, as our
hearing thresholds haven't improved. CD removed the distortions of vinyl
reproduction, but we're still left with the limitations of loudspeakers,
listening rooms, poor recording (and getting worse) and the most fundamental
limitation of all in my view that stereo or surround does not recreate a
convincing soundfield for the listener. We will need a completely new way
of generating sounds at home, not using discrete loudspeakers, before we can
realistically recreate a complete soundfield.

However, the improvements in sound reproduction have bored some, who have
returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

S.

--
http://audiopages.googlepages.com

how good are class D amplifiers?
 

In article ,
Rob wrote:
It could just be that certain modes of reproduction produce a more
satisfying result. A painter's rendition, a musician's performance, a
poet's meter, a writer's (etc). These examples may result in a more
satisfying, more *realistic*, experience of the original event, despite
the fact their efforts are not technically facsimiles.

Is distortion always bad?

No. A fairly classic example was over driving analogue tape with open
brass to get more 'edge'.

Trouble is with a home system is that most use it for a variety of stuff.
And whilst a coloured speaker, for example, might sound ok on some stuff
it will be very tiring on speech.

--
*Why don't sheep shrink when it rains?

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

In article ,
Serge Auckland wrote:
We will need a completely new way of generating sounds at home, not
using discrete loudspeakers, before we can realistically recreate a
complete soundfield.

Ambisonics come close using conventional speakers. At a cost.

However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

There could well be something in that. When I started playing around with
audio, the norm in a domestic environment was pretty poor. FM radio was
near non existent, and TVs had poor loudspeakers. Record players had small
loudspeakers driven off SET valve amps ;-) with pretty nasty crystal
pickups. So it was relatively easy to bring about a real improvement which
gave one a great deal of pleasure. Not so easy these days given even a
modest but decent sound system straight out of the box.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

"Keith G" wrote in message

"Rob" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and
distortion figures on record (Martin Colloms) yet,
last night when I was listening to a particularly fine
1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s
to my 2A3 SET on the Fidelios and got a much better,
more *exciting* (more listenable) sound. As the SET
(according to the pundits here) produces enough
distortion to bend light and the Fidelios have little
or nothing outside the range of the human voice, I am
intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up
on the their telly
for that 'technicolor' look. So actually preferring
some types of distortion doesn't seem that unusual to
me. That's why so many like vinyl,
after all.


It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction
produce a more satisfying result. A painter's rendition,
a musician's performance, a poet's meter, a writer's
(etc). These examples may result in a more satisfying,
more *realistic*, experience of the original event,
despite the fact their efforts are not technically
facsimiles. Is distortion always bad?


The instant you touch a volume control you distort the
sound to suit your needs....

Contrary to the author's apparent belief, it is possible to play a recording
at the same SPL as it was recorded.

However, if you took what he said seriously, the instant you choose a
listening location at a live concert, you distort the sound to suit your
needs.

how good are class D amplifiers?
 

"Dave Plowman (News)" wrote in message
...
In article ,
Serge Auckland wrote:
We will need a completely new way of generating sounds at home, not
using discrete loudspeakers, before we can realistically recreate a
complete soundfield.

Ambisonics come close using conventional speakers. At a cost.

However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

There could well be something in that. When I started playing around with
audio, the norm in a domestic environment was pretty poor. FM radio was
near non existent, and TVs had poor loudspeakers. Record players had small
loudspeakers driven off SET valve amps ;-) with pretty nasty crystal
pickups. So it was relatively easy to bring about a real improvement which
gave one a great deal of pleasure. Not so easy these days given even a
modest but decent sound system straight out of the box.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

--

Ambisonics came closer than quadrophonics did, but still relied on a small
number of loudspeakers, and the creation of phantom images between the
loudspeakers to fill in the gaps between them. A real soundfield is all
around the listener, with sounds coming from an infinite number of
directions.

At the European AES a few years ago, I heard an experimental sound-field
creator which used something like 200 small loudspeakers arranged round the
periphery of a room, each loudspeaker driven from a separate power amp, and
each loudspeaker being given an individual feed off a large DSP driven
routing matrix (the same matrix that's currently in BH as the main and
programme routers and at Bush House). The demo didn't have any height
information, but the surround soundfield was most impressively realistic.
One demo was of a city street recorded with the Soundfield microphone and
then synthesised in the room. It was the most realistic portrayal I've yet
heard. Walking round the room gave the same sort of effect as walking around
in the open air in a city. To be complete it would have needed several
hundred more sound sources to portray height, but the principle was sound.

Clearly this sort of system wouldn't be domestically acceptable, but I think
we have to get away from the current paradigm of 2 or 4/5 or even 6/7
loudspeakers and to some sort of sound-field synthesiser if recorded music
is to make real progress. Can't see it happening though, as the concept of
listening to music in one place, without distraction seems as old-hat as
wearing spats.

S.

--
http://audiopages.googlepages.com
http://audiopages.googlepages.com

how good are class D amplifiers?
 

On Mon, 21 May 2007 20:14:05 +0100, "Serge Auckland"
wrote:

"Dave Plowman (News)" wrote in message
...
In article ,
Serge Auckland wrote:
We will need a completely new way of generating sounds at home, not
using discrete loudspeakers, before we can realistically recreate a
complete soundfield.

Ambisonics come close using conventional speakers. At a cost.

However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

There could well be something in that. When I started playing around with
audio, the norm in a domestic environment was pretty poor. FM radio was
near non existent, and TVs had poor loudspeakers. Record players had small
loudspeakers driven off SET valve amps ;-) with pretty nasty crystal
pickups. So it was relatively easy to bring about a real improvement which
gave one a great deal of pleasure. Not so easy these days given even a
modest but decent sound system straight out of the box.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

--

Ambisonics came closer than quadrophonics did, but still relied on a small
number of loudspeakers, and the creation of phantom images between the
loudspeakers to fill in the gaps between them. A real soundfield is all
around the listener, with sounds coming from an infinite number of
directions.

At the European AES a few years ago, I heard an experimental sound-field
creator which used something like 200 small loudspeakers arranged round the
periphery of a room, each loudspeaker driven from a separate power amp, and
each loudspeaker being given an individual feed off a large DSP driven
routing matrix (the same matrix that's currently in BH as the main and
programme routers and at Bush House). The demo didn't have any height
information, but the surround soundfield was most impressively realistic.
One demo was of a city street recorded with the Soundfield microphone and
then synthesised in the room. It was the most realistic portrayal I've yet
heard. Walking round the room gave the same sort of effect as walking around
in the open air in a city. To be complete it would have needed several
hundred more sound sources to portray height, but the principle was sound.

Clearly this sort of system wouldn't be domestically acceptable, but I think
we have to get away from the current paradigm of 2 or 4/5 or even 6/7
loudspeakers and to some sort of sound-field synthesiser if recorded music
is to make real progress. Can't see it happening though, as the concept of
listening to music in one place, without distraction seems as old-hat as
wearing spats.

S.

As I understand it Ambisonics is a system to encode directional
information, 3 channels can encode from any direction in a plane
accurately and 4 channels can encode sound coming from any direction
on a sphere accurately.

The reproduction decoder is a seperate function from the recording and
it has always been recognised that the more speakers the better, but
practicallity dictates that commercial decoders are designed to drive
a small number of speakers. However, ISTR that the WW/Integrex decoder
of about 1978 was capable of driving 6 speakers and the current
Meridian designs can drive 7 speakers. There are other non-commercial
decoder designs that can drive many more speakers.

Improving image accuracy with multiple drivers has been tried even
with normal 2 channel systems. E J Jordan described a system using
many drive units arranged in a horizontal line. The speakers were
linked with delay lines, the left signal went in one end, the right in
the other. He claimed that the result gave very accurate imaging
independent of listening position. If it worked as he claimed it
should have been a significant improvement over normal 2 speaker
stereo.

Bill

how good are class D amplifiers?
 

In article , Dave Plowman (News)
writes
In article ,
Serge Auckland wrote:
We will need a completely new way of generating sounds at home, not
using discrete loudspeakers, before we can realistically recreate a
complete soundfield.

Ambisonics come close using conventional speakers. At a cost.

However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

There could well be something in that. When I started playing around with
audio, the norm in a domestic environment was pretty poor. FM radio was
near non existent, and TVs had poor loudspeakers. Record players had small
loudspeakers driven off SET valve amps ;-) with pretty nasty crystal
pickups. So it was relatively easy to bring about a real improvement which
gave one a great deal of pleasure.


Not so easy these days given even a
modest but decent sound system straight out of the box.

Including yer DABble radio eh Dave;?...


--
Tony Sayer

how good are class D amplifiers?
 

"Arny Krueger" wrote in message
...
"Keith G" wrote in message

"Rob" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Keith G wrote:
It is reputed to have some of the lowest noise and
distortion figures on record (Martin Colloms) yet,
last night when I was listening to a particularly fine
1958 recording of Grieg's Concerto in A minor
(Solomon), I switched from the Technics on the TLS80s
to my 2A3 SET on the Fidelios and got a much better,
more *exciting* (more listenable) sound. As the SET
(according to the pundits here) produces enough
distortion to bend light and the Fidelios have little
or nothing outside the range of the human voice, I am
intrigued as to what's going on?

Is it me?

Almost certainly.

Plenty of people prefer the colour saturation turned up
on the their telly
for that 'technicolor' look. So actually preferring
some types of distortion doesn't seem that unusual to
me. That's why so many like vinyl,
after all.


It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction
produce a more satisfying result. A painter's rendition,
a musician's performance, a poet's meter, a writer's
(etc). These examples may result in a more satisfying,
more *realistic*, experience of the original event,
despite the fact their efforts are not technically
facsimiles. Is distortion always bad?


The instant you touch a volume control you distort the
sound to suit your needs....

Contrary to the author's apparent belief, it is possible to play a
recording at the same SPL as it was recorded.

However, if you took what he said seriously, the instant you choose a
listening location at a live concert, you distort the sound to suit
your needs.


I refrained from adding to a recent thread that was getting a bit
carried away with the subject of 'realistic reproduction of an
orchestra' in one's own listening room - fuelling the notion that there
is only one true, accurate (distortion free) rendition of (presumably)
every single piece of music ever composed or created. Farcical, to say
the least - I have as many as half a dozen *different* recordings of
some works and can therefore distort the sound (and runtime) by choosing
whichever one to play...

how good are class D amplifiers?
 

"Serge Auckland" wrote in message
...
"Rob" wrote


Is distortion always bad?

Is distortion always bad? Now there's an interesting question.



It certainly is - I have often wondered why some people run away
shrieking at the mention of the word 'distortion' like it's a contagion
when it only describes a characteristic of non-linearity and one which
is ultimately inescapable...??



However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up
some excitement. So, plenty to exercise us.


The words 'dull' and 'bland' are the ones that come to mind when I think
of the sound of some of the 'blameless' kit playing certain (most) CDs -
so shoot us for wanting/seeking summat a little more *emotionally
involving*...!!

Proof of the pudding? Give a person a CD to play on an SS system and
give him the remote control - then wait and see how long before he/she
starts 'track skipping'...

how good are class D amplifiers?
 

"Bill Taylor" wrote in message
...
On Mon, 21 May 2007 20:14:05 +0100, "Serge Auckland"
wrote:

"Dave Plowman (News)" wrote in message
...
In article ,
Serge Auckland wrote:
We will need a completely new way of generating sounds at home, not
using discrete loudspeakers, before we can realistically recreate a
complete soundfield.

Ambisonics come close using conventional speakers. At a cost.

However, the improvements in sound reproduction have bored some, who
have returned to very obsolete technology in an attempt to stir up some
excitement. So, plenty to exercise us.

There could well be something in that. When I started playing around
with
audio, the norm in a domestic environment was pretty poor. FM radio was
near non existent, and TVs had poor loudspeakers. Record players had
small
loudspeakers driven off SET valve amps ;-) with pretty nasty crystal
pickups. So it was relatively easy to bring about a real improvement
which
gave one a great deal of pleasure. Not so easy these days given even a
modest but decent sound system straight out of the box.

--
*I am a nobody, and nobody is perfect; therefore I am perfect*

Dave Plowman London SW
To e-mail, change noise into sound.

--

Ambisonics came closer than quadrophonics did, but still relied on a small
number of loudspeakers, and the creation of phantom images between the
loudspeakers to fill in the gaps between them. A real soundfield is all
around the listener, with sounds coming from an infinite number of
directions.

At the European AES a few years ago, I heard an experimental sound-field
creator which used something like 200 small loudspeakers arranged round
the
periphery of a room, each loudspeaker driven from a separate power amp,
and
each loudspeaker being given an individual feed off a large DSP driven
routing matrix (the same matrix that's currently in BH as the main and
programme routers and at Bush House). The demo didn't have any height
information, but the surround soundfield was most impressively realistic.
One demo was of a city street recorded with the Soundfield microphone and
then synthesised in the room. It was the most realistic portrayal I've yet
heard. Walking round the room gave the same sort of effect as walking
around
in the open air in a city. To be complete it would have needed several
hundred more sound sources to portray height, but the principle was sound.

Clearly this sort of system wouldn't be domestically acceptable, but I
think
we have to get away from the current paradigm of 2 or 4/5 or even 6/7
loudspeakers and to some sort of sound-field synthesiser if recorded
music
is to make real progress. Can't see it happening though, as the concept of
listening to music in one place, without distraction seems as old-hat as
wearing spats.

S.

As I understand it Ambisonics is a system to encode directional
information, 3 channels can encode from any direction in a plane
accurately and 4 channels can encode sound coming from any direction
on a sphere accurately.

The reproduction decoder is a seperate function from the recording and
it has always been recognised that the more speakers the better, but
practicallity dictates that commercial decoders are designed to drive
a small number of speakers. However, ISTR that the WW/Integrex decoder
of about 1978 was capable of driving 6 speakers and the current
Meridian designs can drive 7 speakers. There are other non-commercial
decoder designs that can drive many more speakers.

Improving image accuracy with multiple drivers has been tried even
with normal 2 channel systems. E J Jordan described a system using
many drive units arranged in a horizontal line. The speakers were
linked with delay lines, the left signal went in one end, the right in
the other. He claimed that the result gave very accurate imaging
independent of listening position. If it worked as he claimed it
should have been a significant improvement over normal 2 speaker
stereo.

Bill

The Ambisonics record process is, as you say, able to capture the complete
soundfield at one point. What it can't do, is sample the soundfield at
multiple (ideally every) points in a hall. Reproduction through a small
number of 'speakers (whether 2, 7 or even 17) can't reproduce the soundfield
accurately if it relies on the creation of phantom images to fill in the
gaps between the small number of 'speakers.

Jordan's experiments were interesting at the time, but to have got a really
significant improvement would have required as many reproduce channels as he
had drive units, and using soundfield recordings and decoding to match.

As much as I can dream, I can't see it happening, not for technological
reasons which are daunting enough, but for social reasons, i.e. there aren't
enough people interested in sitting and listening to music to make it
commercially viable.

S.

--
http://audiopages.googlepages.com

how good are class D amplifiers?
 

In article ,
tony sayer wrote:
Not so easy these days given even a
modest but decent sound system straight out of the box.

Including yer DABble radio eh Dave;?...

No one is forcing you to listen to DAB, and never will. If you don't like
it for anything use one of the alternatives. You're obviously in the
enviable position of having perfect reception off FM both at home and in
the car - or more likely are so used to the distortion caused by multipath
you don't notice it anymore.

--
*Learn from your parents' mistakes - use birth control.

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

In article ,
Keith G wrote:
Proof of the pudding? Give a person a CD to play on an SS system and
give him the remote control - then wait and see how long before he/she
starts 'track skipping'...

Might that be that 'remote controls' for LP decks tend to be like hen's
teeth?

--
*When did my wild oats turn to prunes and all bran?

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
Proof of the pudding? Give a person a CD to play on an SS system and
give him the remote control - then wait and see how long before
he/she
starts 'track skipping'...

Might that be that 'remote controls' for LP decks tend to be like
hen's
teeth?



Here's mine:

http://www.apah69.dsl.pipex.com/show/AiwaRemote.JPG


Fits this deck (far right, under the name badge on the fascia panel):

http://www.apah69.dsl.pipex.com/show/AiwaDeck.JPG


If there was (or had been) a market for them, they would have been more
widely available...

how good are class D amplifiers?
 

On 2007-05-21, Serge Auckland wrote:
"Rob" wrote in message
...
It's all 'reproduction', and it all 'distorts'.

It could just be that certain modes of reproduction produce a more
satisfying result. A painter's rendition, a musician's performance, a
poet's meter, a writer's (etc). These examples may result in a more
satisfying, more *realistic*, experience of the original event, despite
the fact their efforts are not technically facsimiles.

Is distortion always bad?

Is distortion always bad? Now there's an interesting question.

For me yes, High Fidelity sound reproduction for me has been constant battle
to identify forms of distortion and eliminate them. When I first started in
Hi-Fi, few amplifiers were "transparent", and bit by bit they improved such
that by the mid '80s, no further subjective improvement became possible.
Amplifiers since have become relative cheaper, more reliable and higher
powered, but performance hasn't improved, in fact can't improve, as our
hearing thresholds haven't improved. CD removed the distortions of vinyl
reproduction, but we're still left with the limitations of loudspeakers,
listening rooms, poor recording (and getting worse) and the most fundamental
limitation of all in my view that stereo or surround does not recreate a
convincing soundfield for the listener. We will need a completely new way
of generating sounds at home, not using discrete loudspeakers, before we can
realistically recreate a complete soundfield.

I was very happy to replace my vinyl kit with CD. I was never really
satisfied with the vinyl sound (let alone the inconvenience). While I
prioritize music above sound, the fundamental technical inaccuracies
of vinyl sound continually nagged me - perhaps from being a regular
concert-goer and having that sound as my reference. I didn't realize
how bad it was until CD arrived.

When you look at the level of harmonic distortion from even an expensive
cartridge (0.5% to 1%) and add that to the harmonic distortion from
unavoidable geometry errors from a normal pivoted arm (another 1% at
peak - it's only zero at two points on a LP) then it's clear why.

And then if you have any cartridge and arm alignment errors, even in
the 1 degree and 1 mm range, the harmonic distortion rises again -
by another 0.5-2%.

It all adds up and is very audible (to me anyway).

--
John Phillips

how good are class D amplifiers?
 

In article ,
Keith G wrote:
Might that be that 'remote controls' for LP decks tend to be like
hen's
teeth?

Here's mine:

http://www.apah69.dsl.pipex.com/show/AiwaRemote.JPG


Fits this deck (far right, under the name badge on the fascia panel):

http://www.apah69.dsl.pipex.com/show/AiwaDeck.JPG


If there was (or had been) a market for them, they would have been more
widely available...

And this allows you to instantly change tracks as does a CD one?

--
*I brake for no apparent reason.

Dave Plowman London SW
To e-mail, change noise into sound.

how good are class D amplifiers?
 

"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:

"Rob" wrote in message
...


Many thanks - copied to file for future reference! I'm still confused
by 'power'. This is presumably covered to a point with your
distortion criterion, but I remain to be convinced that most
amplifiers are by any means linear as the volume goes up.

How can they not be? Non-linearity causes amongst other things harmonic
distortion, so provided the THD is below 0.1%, then the linearity is
similarly assured.

I am slightly wary of the above statement. If you are using THD as a guide
I'd prefer to explicitly extend it over a range of frequencies and powers
*and* to various types of load. The reason being various types of
'dynamic'
nonlinearity which the figures might otherwise miss.

I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at harmonics of
the test frequency in most cases. I've seen amps where the THD value was
low, but where there was much more LF garbage due to this.

Slainte,

Jim


Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers and
all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters actually
measure. Of course the use of a harmonic analyser for distortion measurement
won't pick up the +N component, but as a practicing engineer, I found the
use of such an instrument to be tedious in the extreme, and unnecessary when
an overall THD+N figure was so easily achieved.

S.

how good are class D amplifiers?
 

On Tue, 22 May 2007 09:19:09 +0100, "Serge Auckland"
wrote:



"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:

"Rob" wrote in message
...


Many thanks - copied to file for future reference! I'm still confused
by 'power'. This is presumably covered to a point with your
distortion criterion, but I remain to be convinced that most
amplifiers are by any means linear as the volume goes up.

How can they not be? Non-linearity causes amongst other things harmonic
distortion, so provided the THD is below 0.1%, then the linearity is
similarly assured.

I am slightly wary of the above statement. If you are using THD as a guide
I'd prefer to explicitly extend it over a range of frequencies and powers
*and* to various types of load. The reason being various types of
'dynamic'
nonlinearity which the figures might otherwise miss.

I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at harmonics of
the test frequency in most cases. I've seen amps where the THD value was
low, but where there was much more LF garbage due to this.

Slainte,

Jim


Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers and
all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters actually
measure. Of course the use of a harmonic analyser for distortion measurement
won't pick up the +N component, but as a practicing engineer, I found the
use of such an instrument to be tedious in the extreme, and unnecessary when
an overall THD+N figure was so easily achieved.

S.


The problem becomes more complex when you use an FFT analyser, as I
suspect most are these days. You then need to consider the number of
points in the FFT, and the way they display noise. Discrete signals
are easy - whatever you do with the FFT, they look the same size, but
the "+noise" bit will change with the number of points. So you need to
interpret rather than just read the numbers on the screen. It may be
that some systems will make an effort to do this, but I suspect that
when noise and distortion aren't too far apart, they won't make too
good a job of it.

Are there many distortion analysers any more that simply null the
fundamental and display the sum of the rest?

d

--
Pearce Consulting
http://www.pearce.uk.com

how good are class D amplifiers?
 

"Don Pearce" wrote in message
...
On Tue, 22 May 2007 09:19:09 +0100, "Serge Auckland"
wrote:



"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:

"Rob" wrote in message
...


Many thanks - copied to file for future reference! I'm still
confused
by 'power'. This is presumably covered to a point with your
distortion criterion, but I remain to be convinced that most
amplifiers are by any means linear as the volume goes up.

How can they not be? Non-linearity causes amongst other things harmonic
distortion, so provided the THD is below 0.1%, then the linearity is
similarly assured.

I am slightly wary of the above statement. If you are using THD as a
guide
I'd prefer to explicitly extend it over a range of frequencies and
powers
*and* to various types of load. The reason being various types of
'dynamic'
nonlinearity which the figures might otherwise miss.

I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at harmonics
of
the test frequency in most cases. I've seen amps where the THD value was
low, but where there was much more LF garbage due to this.

Slainte,

Jim


Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers and
all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters
actually
measure. Of course the use of a harmonic analyser for distortion
measurement
won't pick up the +N component, but as a practicing engineer, I found the
use of such an instrument to be tedious in the extreme, and unnecessary
when
an overall THD+N figure was so easily achieved.

S.


The problem becomes more complex when you use an FFT analyser, as I
suspect most are these days. You then need to consider the number of
points in the FFT, and the way they display noise. Discrete signals
are easy - whatever you do with the FFT, they look the same size, but
the "+noise" bit will change with the number of points. So you need to
interpret rather than just read the numbers on the screen. It may be
that some systems will make an effort to do this, but I suspect that
when noise and distortion aren't too far apart, they won't make too
good a job of it.

Are there many distortion analysers any more that simply null the
fundamental and display the sum of the rest?

d

--
Pearce Consulting
http://www.pearce.uk.com

Most if not all of the legacy distortion analysers will be of the nulling
sort, and lab test gear has a very long life so I suspect (but don't know
for sure) that a very high proportion of distortion analysers in regular use
are still of that sort. Today's sales of test equipment are relatively very
low. Studios and broadcasters rarely buy new audio test gear as they already
have instruments for their remaining analogue stuff, and all this new
digital stuff either works or it doesn't, and anyway, if it goes wrong it
needs someone from the factory to come and see to it. When I worked for an
audio test equipment manufacturer some 10-12 years ago, it was by then
already clear that very little new audio test equipment was being sold. I
think we made more money from the recalibration charges on the existing
installed park than from selling new equipment.

S.

--
http://audiopages.googlepages.com

how good are class D amplifiers?
 

On Tue, 22 May 2007 09:33:16 +0100, "Serge Auckland"
wrote:

Are there many distortion analysers any more that simply null the
fundamental and display the sum of the rest?

d

--
Pearce Consulting
http://www.pearce.uk.com

Most if not all of the legacy distortion analysers will be of the nulling
sort, and lab test gear has a very long life so I suspect (but don't know
for sure) that a very high proportion of distortion analysers in regular use
are still of that sort. Today's sales of test equipment are relatively very
low. Studios and broadcasters rarely buy new audio test gear as they already
have instruments for their remaining analogue stuff, and all this new
digital stuff either works or it doesn't, and anyway, if it goes wrong it
needs someone from the factory to come and see to it. When I worked for an
audio test equipment manufacturer some 10-12 years ago, it was by then
already clear that very little new audio test equipment was being sold. I
think we made more money from the recalibration charges on the existing
installed park than from selling new equipment.

OK. Kind of surprising, though, as just about everybody now possesses
a distortion meter at least as good as a nulling type. I'm talking
about a PC sound card, of course. Just needs suitable software.

d

--
Pearce Consulting
http://www.pearce.uk.com