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

Arcam? No idea - I've just bought a brand new Denon PMA-655R amp in my
'SS revisited' quest for best sound from the smaller of the Firewood
Horns!! (Bloody SS seems to grip the smaller, less sensitive drive
units better!!) I am under the impresion that it's an OK amp with a
particularly good Phono Stage - anyone care to confirm or shoot that
down?
**Personally, I would spend the same Bucks (Squid) on a Rotel, as your
Denon fairly 'screams' in the HF. IOW: It's just another Asian amp,
with a pretty face. Now, if you'd dropped a few more Squid for the
PMA1500AE, then THAT is a whole 'nuther cricket match. It is a very
bloody good amp, with an excellent phono stage. And I'm here to tell
you that I am not a lover of MOSFET amps, but the PMA1500AE is pretty
damned good. As usual, with all the recent generation Denon tuners,
it's matching partner is an absolute gem. In fact, the new Denon tuners
make some of the old stalwarts (Yamaha T2, Tandberg, et al) sound
pretty damned ordinary. And they don't cost the Earth either.

So, in short, you should have spent a few more Squid for something
really nice, instead of another (ho-hum) Asian amp.


OK Trevor, thanks for that - most interesing, but 'few more'..? Bugger,
the 1500AE is over *double* what I paid for the 655!!

**It's well worth it. In fact, you might find yourself selling off some
of your glass things to pay for it. It is a very good amp.


I don't follow this, and remain pretty confused about the whole SS
pantomime. Apart from build quality (that 7-odd kg has to go somewhere)
what has that amp got that improves the way it amplifies, and hence sound?

**Quite a bit, actually. It is not all that difficult to coax bad behaviour
from an amplifier which performs perfectly into a perfectly resistive load.
Since few loudspeakers act like resistors, you can readily appreciate why
amplifier can sound different, yet measure similarly.


On the one hand, I gather from technical people on this ng that all amps
which 1) drive a 2 ohm load at 3 times the maximum 8 ohm power (100W 8
ohm, 300W 2 ohm at 1% THD for 3 seconds for example); *and* 2) are
properly designed and manufactured (nearly all of the big name stuff
nowadays), will sound identical. I doubt any Denon achieves (1) btw.

**The magic words in this statement a "...are properly designed and
manufactured.."


On the other hand, it's not hard to find plenty of reviews and anecdotes
that suggest amplifiers at a given spec do sound different.

Curious - is there any defining factor in your opinion?!

**Sure. Measuring speakers into actual loudspeakers can reveal differences
which may be quite audible.


My curiosity here was to compare the Denon with the Argos POS I have
been using (having compared CDPs) and I have reduced this stack:

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

To this:

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

(See how the 'spares' are created!!?? :-)

And I tell you summat - listening askance, with my back turned and eyes
shut at midnight on a foggy day and somebody else working the throttle,
I couldn't tell 'em apart!! The '30W' Argos amp weighs 5.3 kg and costs
60 quid, the '50W' Denon weighs 7.0 kg and costs 250 quid (list)!!
(Where do they get these bloody power output figures from? - I got an 8
watt 300B SET that will blow *both* of them into the weeds!!)

**Yeah, sure.


Well, possibly! Comparing a 100W valve amp and a 140W SS - the valve amp
is simply louder.

**Sometimes, yes. But Keith was talking about an EIGHT WATT amp vs a 50 Watt
amp. BIG difference. The reality is that the SPL difference between two,
otherwise identical, 100 Watt and 140 Watt amps will be barely audible. The
differences you refer to, with valve amps are mostly as follows:

1) Valve amps tend to clip (Voltage limit) rather gracefully. Thus they can
be driven further into clipping, without obvious 'nastiness' and an increase
in average SPL.
2) Valve amps tend to possess a more benign current limit characteristic,
due to the abscence of current limit systems, which are normally used in
(BJT) transistor amps.
3) Valve amps, by virtue of their higher Voltages, tend to have quite large
energy storage systems (the equation is: 1/2CV^2), though the actual
capacitance seems to be quite small. Additionally, the capacitors used in
valve amps tend to possess lower ESL figures.
4) Valve amps require the use of large power transformers, in order to
supply filament supplies. This means more iron and thus energy storage in
the power transformer itself.

1) Can be compensated for with transistor amps, via several mechanisms, but
rarely is.
2) Can be compensated for, but it rarely done in transistor amps.
3) Can be compensated for, by adding more, small value capacitors.
4) Can be compensated for by using larger transformers.

It's not that difficult. The manufacturer needs to spend a little money on
the design. IOW: In general terms, if the manufacturer has performed the
above and the consumer is willing to spend more money, a 100 Watt transistor
amp will sound just as loud as a 100 Watt valve amp. It's all about money.
Valve amp owners seem prepared to spend more on big valve amps than they do
on equivalent transistor amps. They then proclaim that the transistor amp
sounds worse, even though it was half the price. Sheesh!


Go figure (as they say)...!!

(OK, The Denon sits at 50% volume while the Argos amp is at 90% into the
stubborn little horns....)

Incidentally, I can see why SS users might not like horns - there is a
tendancy to a little 'honkiness' with them that you don't get with
valves...??!! But, contrary to what one or two here would have you
believe, us 'valvies' are not so bigotted - I love these amps and for a
few weeks in every year, it's nice to run an SS amp and soft top car!!
(Well, the days of me having a nice little soft top in the barn are long
gone, but I can still afford an SS amp or two!! :-)

**Then choose a decent SS amp.

Here's my last bit of Show N Tell for the day - the kid (my oldest) in
this car is 30 now!!

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

**Oh dear. I was hoping for a Morgan, at least. MGs are so passe'. They
always sounded better than they went. Back in the day, one of my mates
owned and MGB and the other a Datsun Princess. The Datsun could easily
pull 120MPH and the MG, well...... Not so fast. Let's not even get
started on oil leaks. Did Pommy car builders ever manage to build oil
seals which, well, sealed? And this is from one who has owned four
Escorts. Not one of them could keep the oil where it belonged.

Now back to earth with a bump - I gotta go and make a start on the
fascia boards and guttering now!! :-(

**Don't get me started. I just moved to a new home and we now live the
most beautiful part of Sydney. Lots of trees (and possums, Magpies,
Cockatoos, et al). The gutters glog every fime mins or so. Since it is a
two story place and I don't espically enjoy crawling around the roof 5
Metres off the ground, I got a quote for this fancy new non-clog
guttering (it really is very clever stuff).

http://www.easyflow.com.au/

Better than clever, actually. It's brilliant. FIFTEEN GRAND!!!! Yikes!
Nice product, but jeez. Maybe I'll keep climbing ladders for a bit
longer.


Leaf blockage?

**Yup.


--
Trevor Wilson
www.rageaudio.com.au



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

Jim Lesurf wrote:
In article , Rob
wrote:
[snip]

On the one hand, I gather from technical people on this ng that all amps
which 1) drive a 2 ohm load at 3 times the maximum 8 ohm power (100W 8
ohm, 300W 2 ohm at 1% THD for 3 seconds for example); *and* 2) are
properly designed and manufactured (nearly all of the big name stuff
nowadays), will sound identical.

I'm not sure which "technical people" would say that. In reality some other
conditions might need to be satisfied before amps would "sound indentical"
in use. However see below... :-)


Well, and would you believe it, I can't find the reference. It was one
of those huge threads on this ng about 2 years ago, and it included that
nugget of information which went unchallenged. I think, ahem, it was
Stewart P.

I doubt any Denon achieves (1) btw.

On the other hand, it's not hard to find plenty of reviews and anecdotes
that suggest amplifiers at a given spec do sound different.

Curious - is there any defining factor in your opinion?!

The problem is that although there are many, many such "reviews and
anecdotes", there seems to be a dearth of any reliable evidence to support
such claims in many cases. Magazine reviewers often make statements about
the differences they (claim they) can hear between amps. But when listening
comparison tests have been carried out which conform to some fairly basic
requirements, they seem to be unable to tell one amp from another *simply
on the basis of the sounds*. Thus for all we know they are responding to
other 'differences' which have nothing to do with the amps as such, or to
the name badges...

Alas, if the reviewers had to start saying they couldn't generally hear any
such differences, they may find they'd have to write about something
else... :-)


Yes, you're quite right of course. The problem for mugs like me is
trying to figure out what, exactly, matters when buying a SS amp. The
'3X' rule seemed to make a certain amount of sense at the time, so I
banked that as 'significant variable'.

I'm not sure any domestic amp at less than house prices actually does
this 3X thing. Having read a few reviews with this in mind manufacturers
tend to, for example, shift the distortion decimal point one place to
the right when quoting power at lower impedences, or simply (and
modestly) underspecify the 8 ohm figure to 'reveal' the magic 'doubling
up' (Krell comes to mind).

I have to say I'm pretty sure I can hear differences between amplifiers
that should sound the same, particularly at louder volumes. Thing is, if
I can - and I'm not taking that as a given! - why?

Rob

Trevor Wilson wrote:
"Rob" wrote in message

snip

I don't follow this, and remain pretty confused about the whole SS
pantomime. Apart from build quality (that 7-odd kg has to go somewhere)
what has that amp got that improves the way it amplifies, and hence sound?

**Quite a bit, actually. It is not all that difficult to coax bad behaviour
from an amplifier which performs perfectly into a perfectly resistive load.
Since few loudspeakers act like resistors, you can readily appreciate why
amplifier can sound different, yet measure similarly.


Readily appreciate eh :-)

On the one hand, I gather from technical people on this ng that all amps
which 1) drive a 2 ohm load at 3 times the maximum 8 ohm power (100W 8
ohm, 300W 2 ohm at 1% THD for 3 seconds for example); *and* 2) are
properly designed and manufactured (nearly all of the big name stuff
nowadays), will sound identical. I doubt any Denon achieves (1) btw.

**The magic words in this statement a "...are properly designed and
manufactured.."


I think the point here is that virtually all amplifiers from major
manufacturers are properly designed and manufactured - that's what I'm
led to believe.

On the other hand, it's not hard to find plenty of reviews and anecdotes
that suggest amplifiers at a given spec do sound different.

Curious - is there any defining factor in your opinion?!

**Sure. Measuring speakers into actual loudspeakers can reveal differences
which may be quite audible.


That sounds fair enough - is there a particular measurement that stands out?

My curiosity here was to compare the Denon with the Argos POS I have
been using (having compared CDPs) and I have reduced this stack:

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

To this:

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

(See how the 'spares' are created!!?? :-)

And I tell you summat - listening askance, with my back turned and eyes
shut at midnight on a foggy day and somebody else working the throttle,
I couldn't tell 'em apart!! The '30W' Argos amp weighs 5.3 kg and costs
60 quid, the '50W' Denon weighs 7.0 kg and costs 250 quid (list)!!
(Where do they get these bloody power output figures from? - I got an 8
watt 300B SET that will blow *both* of them into the weeds!!)
**Yeah, sure.

Well, possibly! Comparing a 100W valve amp and a 140W SS - the valve amp
is simply louder.

**Sometimes, yes. But Keith was talking about an EIGHT WATT amp vs a 50 Watt
amp. BIG difference. The reality is that the SPL difference between two,
otherwise identical, 100 Watt and 140 Watt amps will be barely audible. The
differences you refer to, with valve amps are mostly as follows:

1) Valve amps tend to clip (Voltage limit) rather gracefully. Thus they can
be driven further into clipping, without obvious 'nastiness' and an increase
in average SPL.
2) Valve amps tend to possess a more benign current limit characteristic,
due to the abscence of current limit systems, which are normally used in
(BJT) transistor amps.
3) Valve amps, by virtue of their higher Voltages, tend to have quite large
energy storage systems (the equation is: 1/2CV^2), though the actual
capacitance seems to be quite small. Additionally, the capacitors used in
valve amps tend to possess lower ESL figures.
4) Valve amps require the use of large power transformers, in order to
supply filament supplies. This means more iron and thus energy storage in
the power transformer itself.

1) Can be compensated for with transistor amps, via several mechanisms, but
rarely is.
2) Can be compensated for, but it rarely done in transistor amps.
3) Can be compensated for, by adding more, small value capacitors.
4) Can be compensated for by using larger transformers.

It's not that difficult. The manufacturer needs to spend a little money on
the design. IOW: In general terms, if the manufacturer has performed the
above and the consumer is willing to spend more money, a 100 Watt transistor
amp will sound just as loud as a 100 Watt valve amp. It's all about money.
Valve amp owners seem prepared to spend more on big valve amps than they do
on equivalent transistor amps. They then proclaim that the transistor amp
sounds worse, even though it was half the price. Sheesh!


Yes, OK :-)

What I'm driving at is trying to understand the thing that matters - the
'several mechanisms' you refer to. We're (non-techs) given a set of
variables: price, brand (I'd lump kudos, heritage and so on here),
degrees of minimalism, weight, looks, reviews and electrical
specifications. Is there any decent logic that could help determine
which matter?

Go figure (as they say)...!!

(OK, The Denon sits at 50% volume while the Argos amp is at 90% into the
stubborn little horns....)

Incidentally, I can see why SS users might not like horns - there is a
tendancy to a little 'honkiness' with them that you don't get with
valves...??!! But, contrary to what one or two here would have you
believe, us 'valvies' are not so bigotted - I love these amps and for a
few weeks in every year, it's nice to run an SS amp and soft top car!!
(Well, the days of me having a nice little soft top in the barn are long
gone, but I can still afford an SS amp or two!! :-)
**Then choose a decent SS amp.

Here's my last bit of Show N Tell for the day - the kid (my oldest) in
this car is 30 now!!

http://www.apah69.dsl.pipex.com/show/softtop.JPG
**Oh dear. I was hoping for a Morgan, at least. MGs are so passe'. They
always sounded better than they went. Back in the day, one of my mates
owned and MGB and the other a Datsun Princess. The Datsun could easily
pull 120MPH and the MG, well...... Not so fast. Let's not even get
started on oil leaks. Did Pommy car builders ever manage to build oil
seals which, well, sealed? And this is from one who has owned four
Escorts. Not one of them could keep the oil where it belonged.

Now back to earth with a bump - I gotta go and make a start on the
fascia boards and guttering now!! :-(
**Don't get me started. I just moved to a new home and we now live the
most beautiful part of Sydney. Lots of trees (and possums, Magpies,
Cockatoos, et al). The gutters glog every fime mins or so. Since it is a
two story place and I don't espically enjoy crawling around the roof 5
Metres off the ground, I got a quote for this fancy new non-clog
guttering (it really is very clever stuff).

http://www.easyflow.com.au/

Better than clever, actually. It's brilliant. FIFTEEN GRAND!!!! Yikes!
Nice product, but jeez. Maybe I'll keep climbing ladders for a bit
longer.

Leaf blockage?

**Yup.

I can relate to this having just moved to a house with wooden gutters in
the city of trees ;-)

Rob

In article , Rob
wrote:
Jim Lesurf wrote:


The problem is that although there are many, many such "reviews and
anecdotes", there seems to be a dearth of any reliable evidence to
support such claims in many cases.

[snip]


Yes, you're quite right of course. The problem for mugs like me is
trying to figure out what, exactly, matters when buying a SS amp.

Yes. Alas, the root of the problem is that the 'reviewer' may be so eager
to fill the 'review' with his opinions (for which he may have no reliable
evidence, or apply in his situation but not yours) that he may simply not
bother to provide some simpler info that would help you make such
decisions. Readers are then left to 'guess' or simply take the opinions of
the review as if they were a guide...


The '3X' rule seemed to make a certain amount of sense at the time, so I
banked that as 'significant variable'.

For someone *making* power amplifiers it may make sense to design the amp
to be able to deliver high load currents and maintain its voltage output
into 'low loads'. This is because the designer/maker don't know what
speakers all the customers will be using, so have to cater for a range.

But for the *user* if they had the relevant information about their
speakers, and the amp, they could decide how relevant this would be for
them. Alas, the reviews or manufacturer info may not tell you...

I'm not sure any domestic amp at less than house prices actually does
this 3X thing.

You can get quite close to it - provided you have a good power supply and
output devices able to deliver high currents. Also larger heatsinks if the
demand is to be more than for brief peaks. Alas, this means that all
customers have to pay for these things even if only some of them require
them in reality. Hence the temptation for makers to shave away any
'overkill' which most users may never actually require.

[snip]

I have to say I'm pretty sure I can hear differences between amplifiers
that should sound the same, particularly at louder volumes. Thing is, if
I can - and I'm not taking that as a given! - why?

Can't say without much more in the way of specific information. There are
various possible reasons, but without a lot of details I couldn't say if
any of them are relevant. Speculation without data may simply confuse the
issue.

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

"Trevor Wilson" wrote


**Sometimes, yes. But Keith was talking about an EIGHT WATT amp vs a 50
Watt amp. BIG difference. The reality is that the SPL difference between
two, otherwise identical, 100 Watt and 140 Watt amps will be barely
audible. The differences you refer to, with valve amps are mostly as
follows:


OK, to reduce the 'exaggeration' somewhat - the SET in question is actually
rated at 10 watts (?) by the manufacturer - see the cut and paste from the
eBay auction on my webpage:

http://www.apah69.dsl.pipex.com/bez/bezt3b-3.htm

.....and it is certain that it blows the 30W amp away. The *impression* is
that it would blow the 50W amp away also, but I concede this is probably
unlikely and haven't made a direct comparison.

It is not the *loudness* it is the *vastness* of the sound from
valves - subtle difference. But I posted here a while back that two
electricians working here respectively guessed my 2A3 SET (4 watts max) to
be 100 and 200 watts. OK, they weren't 'audiophiles' but they weren't
stupid, either...



It's not that difficult. The manufacturer needs to spend a little money on
the design. IOW: In general terms, if the manufacturer has performed the
above and the consumer is willing to spend more money, a 100 Watt
transistor amp will sound just as loud as a 100 Watt valve amp. It's all
about money. Valve amp owners seem prepared to spend more on big valve
amps than they do on equivalent transistor amps. They then proclaim that
the transistor amp sounds worse, even though it was half the price.
Sheesh!


Reword that thus: "Valve amp owners seem prepared to spend more on big valve
amps than they do on equivalent transistor amps. They then proclaim that the
valve amp sounds better, even though it was double the price." Presents less
of a dilemma that way, doesn't it?

Now, you're the one to ask Trevor, so tell me...

Last night I do believe I got what I suspect* is going to be, yet again, the
best sound ever** by driving my 2A3 SET power amp with the Pre Outs from
the Denon - gives me the 'valve sound' but much bigger (due to the
preamplification, of course) with all mod cons like remote control &c. and
the facility to choose the Denon only on other speakers (2 pairs,
asitappens) for all day background sound and 'summer running'!

So, the question is: Do you think all the 'pre gubbins' - Phono Stage,
controls, knobs, switches, sockets &c. would likely be of equal quality to
the higher priced models you mentioned? (The Phono Stage does seem very
good - certainly good enough for 'background sound', but no comparison with
my valve PS yet...)

I really only wanted the top half of the amp for serious listening and
didn't need/want to pay for unnecessary beef. I'm also gambling that the
'pre' side of an amp like this is going to be effectively *invisible* and I
suspect/believe that this valve/SS hybrid combination will be better than
the other way round - I've tried a valve pre/SS power combo before and it
stinks! (Gives you the worst of both worlds!)


*already know, actually - I'm only being cautious because the drivers are
only a day old yet. See where 'square becomes round' at the bottom of this
page:

http://www.apah69.dsl.pipex.com/fostexfe206e/fostex.htm


** Never surrender, never give in - keep spending....!! :-)

"Keith G" wrote in message
...

"Trevor Wilson" wrote


**Sometimes, yes. But Keith was talking about an EIGHT WATT amp vs a 50
Watt amp. BIG difference. The reality is that the SPL difference between
two, otherwise identical, 100 Watt and 140 Watt amps will be barely
audible. The differences you refer to, with valve amps are mostly as
follows:


OK, to reduce the 'exaggeration' somewhat - the SET in question is
actually
rated at 10 watts (?) by the manufacturer - see the cut and paste from the
eBay auction on my webpage:

http://www.apah69.dsl.pipex.com/bez/bezt3b-3.htm

....and it is certain that it blows the 30W amp away. The *impression* is
that it would blow the 50W amp away also, but I concede this is probably
unlikely and haven't made a direct comparison.

**I also think it unlikely.


It is not the *loudness* it is the *vastness* of the sound from
valves - subtle difference. But I posted here a while back that two
electricians working here respectively guessed my 2A3 SET (4 watts max) to
be 100 and 200 watts. OK, they weren't 'audiophiles' but they weren't
stupid, either...

**Few people can pick the output power ability of an amplifier,in unfamiliar
(or familiar) settings. As you are well aware, a few extra dB of speaker
efficiency can make things very different indeed.




It's not that difficult. The manufacturer needs to spend a little money
on
the design. IOW: In general terms, if the manufacturer has performed the
above and the consumer is willing to spend more money, a 100 Watt
transistor amp will sound just as loud as a 100 Watt valve amp. It's all
about money. Valve amp owners seem prepared to spend more on big valve
amps than they do on equivalent transistor amps. They then proclaim that
the transistor amp sounds worse, even though it was half the price.
Sheesh!


Reword that thus: "Valve amp owners seem prepared to spend more on big
valve amps than they do on equivalent transistor amps. They then proclaim
that the valve amp sounds better, even though it was double the price."
Presents less of a dilemma that way, doesn't it?

**Indeed, but that is the fact. Dollar for Dollar, a transistor can easily
wipe the floor with a valve amp, IF the manufacturer has paid attention to
my earlier comments. Most do not. The reality is this: Valve amps are
designed in specific ways, which are mostly to do with the expense and
limitation inherent to them. Transistor amps are (mostly) designed in
specific ways which relate to the low cost of the active devices themselves.
Imagine, for a moment, that a transistor amp maunfacturer decided to build
his product in such a way that he treated each amplification stage as though
is was very expensive to implement. You would have an amplifier which
combined the strengths of a valve amp (benign Voltage limiting, non-existent
current limiting, huge power supply and load insensitivity) with the obvious
strengths normally associated with a transistor amp ('perfect' frequency
response, inaudible distortion figures, lack of distortion producing output
transformers, etc). THEN you'd have an interseting product. Yes?


Now, you're the one to ask Trevor, so tell me...

Last night I do believe I got what I suspect* is going to be, yet again,
the best sound ever** by driving my 2A3 SET power amp with the Pre Outs
from the Denon - gives me the 'valve sound' but much bigger (due to the
preamplification, of course) with all mod cons like remote control &c. and
the facility to choose the Denon only on other speakers (2 pairs,
asitappens) for all day background sound and 'summer running'!

So, the question is: Do you think all the 'pre gubbins' - Phono Stage,
controls, knobs, switches, sockets &c. would likely be of equal quality to
the higher priced models you mentioned? (The Phono Stage does seem very
good - certainly good enough for 'background sound', but no comparison
with my valve PS yet...)

**Fair question. I have not (yet) opened up either of the two Denon amps in
question, so I can't comment on the topology, nor the quality of the pots
and switches, though it is reasonable to assume that Denon have probably
used an Alps 'Blue Velvet' or equivalent pot in the PMA1500AE and a cheap
carbon pot in the 655. I'll know soon enough, when they start appearing on
my bench for service. I have, however, performed some short listening tests
on both amps, using a Thoren turntable, with a couple of nice cartridges.
The PMA1500AE blew away the 655. The sound was far less hard on my ears with
the 1500, yet, surprisingly, more detailed. I readily admit that I was not
only comparing preamp sections, so the test was not as comprehensive as I
would like it to be. Ideally, I'd have them in my own system for a few days.
Having said that, the difference between the two amps is not subtle. I
sugest to you that if you think the 655 is a good amp, then you have not
heard very many REALLY good amps yet.


I really only wanted the top half of the amp for serious listening and
didn't need/want to pay for unnecessary beef. I'm also gambling that the
'pre' side of an amp like this is going to be effectively *invisible* and
I suspect/believe that this valve/SS hybrid combination will be better
than the other way round - I've tried a valve pre/SS power combo before
and it stinks! (Gives you the worst of both worlds!)

**I understand that you may not have a lot of experience in choosing a good
SS amp yet.



--
Trevor Wilson
www.rageaudio.com.au



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

In article , Keith G
wrote:
[snip]

....and it is certain that it blows the 30W amp away. The *impression*
is that it would blow the 50W amp away also, but I concede this is
probably unlikely and haven't made a direct comparison.

It is not the *loudness* it is the *vastness* of the sound from valves -
subtle difference.

However people are discussing two issues.

One is that some amps may actually give indistinguishable results in given
conditions of use, and that it is possible to provide information to allow
a potential purchaser/user to decide if this is likely when considering a
choice between them.

The other is that some amps have properties which mean they will provide
'altered' results. The user may or may not prefer this.

In both cases, though, the snag is that 'reviews' may simply fail to give
the relevant information, and spout a lot of opinions which might either be
nonsense or not apply to the potential user's situation.

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
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Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Rob
wrote:
Trevor Wilson wrote:


**The magic words in this statement a "...are properly designed and
manufactured.."


I think the point here is that virtually all amplifiers from major
manufacturers are properly designed and manufactured - that's what I'm
led to believe.

It us hard to be sure due to lack of info, but in many cases you are
probably correct. However two amplifiers might deliver indistinguishable
results under some conditions of use, but give different results in other
conditions of use. The most obvious example being a change in speakers and
room, leading to much higher power levels being required.

**Sure. Measuring speakers into actual loudspeakers can reveal
differences which may be quite audible.


That sounds fair enough - is there a particular measurement that stands
out?

For me the obvious ones are the output impedance of the amp, and its
ability to deliver high peak or steady currents with minimal
buzz/distortion. Some reviews give the 4 (and 2) Ohm power levels as a
guide for this, but I would tend to prefer the medium-term current that can
be delivered. e.g. something like 'can deliver X amps RMS for 100 ms' with
the conditions specified.

In some cases you might need to check the stability of the amp, but I'd
hope this would rarely be a concern these days.

Alas, obtaining a full and useful set of results is time-consuming, and
requires both the test gear and the reviewer knowing what the results mean.
It also means they might have to explain their usefulness rather than
simply giving their 'wine tasting' opinions. It also means editors not
worrying that readers would be put off by being expected to read and
understand so as to be able to decide for themselves. Simpler just to
present a 'golden eared opinion'... Even if it has no actual relevance for
the reader. :-/


1) Valve amps tend to clip (Voltage limit) rather gracefully. Thus
they can be driven further into clipping, without obvious 'nastiness'
and an increase in average SPL. 2) Valve amps tend to possess a more
benign current limit characteristic, due to the abscence of current
limit systems, which are normally used in (BJT) transistor amps. 3)
Valve amps, by virtue of their higher Voltages, tend to have quite
large energy storage systems (the equation is: 1/2CV^2), though the
actual capacitance seems to be quite small.

In addition, a valve design may store energy in a series inductor in the
PSU.

However some transistor amps may have quite large amounts of energy and
charge stored in the PSU caps - or may simply use a stabilised supply or be
able to use an extended portion of the mains waveform. Whatever, it just
needs to be 'more than enough' to supply the required audio power. 8-]

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

"Trevor Wilson" wrote


**Fair question. I have not (yet) opened up either of the two Denon amps
in question, so I can't comment on the topology, nor the quality of the
pots and switches, though it is reasonable to assume that Denon have
probably used an Alps 'Blue Velvet' or equivalent pot in the PMA1500AE and
a cheap carbon pot in the 655. I'll know soon enough, when they start
appearing on my bench for service.


OK. My suspicion was that, for cost effectiveness, the pre section
componentry and circuit might be common to most (if not all) of the
range....?


I have, however, performed some short listening tests
on both amps, using a Thoren turntable, with a couple of nice cartridges.
The PMA1500AE blew away the 655. The sound was far less hard on my ears
with the 1500, yet, surprisingly, more detailed. I readily admit that I
was not only comparing preamp sections, so the test was not as
comprehensive as I would like it to be. Ideally, I'd have them in my own
system for a few days. Having said that, the difference between the two
amps is not subtle. I sugest to you that if you think the 655 is a good
amp, then you have not heard very many REALLY good amps yet.


I don't know about it being a *good* amp as such - I'm pleased with it and
it's doing what I bought it for well enough, but I wasn't expecting to get
the 'best amp in the world' for 200 ackers, believe it or not.....




I really only wanted the top half of the amp for serious listening and
didn't need/want to pay for unnecessary beef. I'm also gambling that the
'pre' side of an amp like this is going to be effectively *invisible* and
I suspect/believe that this valve/SS hybrid combination will be better
than the other way round - I've tried a valve pre/SS power combo before
and it stinks! (Gives you the worst of both worlds!)

**I understand that you may not have a lot of experience in choosing a
good SS amp yet.


OK, perhaps you could point me in the right direction, I have had various
models of the following makes of SS amps (in no special order):

Denon
Pioneer
Cambridge Audio
Sony
Yamaha
Cyrus
Marantz
NAD
Quad
Rotel
Technics
JVC
Nikko
Musical Fidelity
Acoustic Solutions
Parasound
Luxman


And also heard these:

Arcam
Roksan
Meridian
Krell


Probably plus a few others I don't remember in each case - and although I
loved each and every one of them (almost) at the time, I wasn't really happy
until I got my first valve amp. Best of that lot above? Possibly the
Meridian Pre/Power Monos, see on the floor in this pic:

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


With a Quad pre/power combo that I heard recently (already forgotten the
'numbers') following very closely, otherwise there's bugger-all to choose
between most of them - they all do the job fairly well and I reckon it comes
down to what 'bells and whistles (and blue LEDs) you get for your money at
the end of the day.

(The truth is, you get a better bang for your buck with a Chinese valve amp
off eBay these days! ;-)

"Keith G" wrote in message
...

"Trevor Wilson" wrote


**Fair question. I have not (yet) opened up either of the two Denon amps
in question, so I can't comment on the topology, nor the quality of the
pots and switches, though it is reasonable to assume that Denon have
probably used an Alps 'Blue Velvet' or equivalent pot in the PMA1500AE
and
a cheap carbon pot in the 655. I'll know soon enough, when they start
appearing on my bench for service.


OK. My suspicion was that, for cost effectiveness, the pre section
componentry and circuit might be common to most (if not all) of the
range....?

**Big mistake. Just listen to one of their HT recievers and compare it to
one of Denon's standalone tuners and you'll see what I mean. The standalone
tuners are very, very good indeed. Gone are the days when manufactuers used
common items in their products. In fact, check the back panel of your 655
and see where it is manufactured. I KNOW that the 1500 originates from
Japan. I also know that the previous model used the Alps 'Blue Velvet'
volume pot. And anyone who klnows these things, knows that they are a very
transparent, long lasting, well matched pot. Standard carbon pots are
something else entirely.



I have, however, performed some short listening tests
on both amps, using a Thoren turntable, with a couple of nice cartridges.
The PMA1500AE blew away the 655. The sound was far less hard on my ears
with the 1500, yet, surprisingly, more detailed. I readily admit that I
was not only comparing preamp sections, so the test was not as
comprehensive as I would like it to be. Ideally, I'd have them in my own
system for a few days. Having said that, the difference between the two
amps is not subtle. I sugest to you that if you think the 655 is a good
amp, then you have not heard very many REALLY good amps yet.


I don't know about it being a *good* amp as such - I'm pleased with it and
it's doing what I bought it for well enough, but I wasn't expecting to get
the 'best amp in the world' for 200 ackers, believe it or not.....

**I believe that you will go out of your way to ensure that you never hear
something truly special, if it contains transistors.





I really only wanted the top half of the amp for serious listening and
didn't need/want to pay for unnecessary beef. I'm also gambling that the
'pre' side of an amp like this is going to be effectively *invisible*
and
I suspect/believe that this valve/SS hybrid combination will be better
than the other way round - I've tried a valve pre/SS power combo before
and it stinks! (Gives you the worst of both worlds!)

**I understand that you may not have a lot of experience in choosing a
good SS amp yet.


OK, perhaps you could point me in the right direction, I have had various
models of the following makes of SS amps (in no special order):

Denon

**From terrible to quite good.

Pioneer

**From terrible to passable.

Cambridge Audio

**Passable.

Sony

**From terrible to quite good.

Yamaha

**From terrible to passable.

Cyrus

**Urk.

Marantz

**From passable to quite good.

NAD

**Passable to quite good.

Quad

**Passable.

Rotel

**Passable to quite good.

Technics

**Urk (though some of their older models were nice..

JVC

**Puke.

Nikko

**Are they still around?

Musical Fidelity

**From shocking to passable.

Acoustic Solutions

**Never heard them.

Parasound

**From ordinary to passable.

Luxman

**Their new stuff? Dunno.



And also heard these:

Arcam

**From respectable to brilliant (their 'Ring DAC' equipped CD players are
breathtakingly good)

Roksan

**Not bad.

Meridian

**Good to very good.

Krell

**Weird sounding to quite good.



Probably plus a few others I don't remember in each case - and although I
loved each and every one of them (almost) at the time, I wasn't really
happy until I got my first valve amp. Best of that lot above? Possibly the
Meridian Pre/Power Monos, see on the floor in this pic:

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


With a Quad pre/power combo that I heard recently (already forgotten the
'numbers') following very closely, otherwise there's bugger-all to choose
between most of them - they all do the job fairly well and I reckon it
comes down to what 'bells and whistles (and blue LEDs) you get for your
money at the end of the day.

(The truth is, you get a better bang for your buck with a Chinese valve
amp off eBay these days! ;-)

**Only in your delusion. I've seen/heard a few and they're simply terrible.


--
Trevor Wilson
www.rageaudio.com.au



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