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

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