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"Amps all sound the same" (more or less)

Arkless Electronics said:
.... 50W for a 100WPC stereo amp but one hell of a lot to get 1WPC in class A yes!
As you'll know there are many benefits to class A beyond being non switching and so not producing crossover distortion and hence many of these non switching topologies are by no means the holy grail of a cool running class A amp! Krell's sustained plateau bias is maybe one of the more successful attempts but still gets hot etc... just less so than permanent class A
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Like to point out the Armstrong 732 circuit. It has the drivers connected to the output along with the output devices. This acts a bit like a 'class A filler'. 8-]
 
Jim Audiomisc said:
I'd suggest that the problem here is trying to consider the 'best' choice of amp *without considering the choice of speakers, etc*.

Thus an amp which is a perfect textbook example of "wire with gain" would sound worse than some other am whose deviations *suited* the choice of speakers, etc. e.g. having an impedance interaction due to non-zero output impedance that combined with the speaker impedance to give a changed response that the user prefer.

The amp designer can't win this battle... unless they also sell you the speakers and decide your room and taste in music. So you have to take these things into account. I'd suggest this is well known the 'science', but people keep persisting in not taking it into account and expect a "one amp to rule them all".

Works for gross problems, but not for interaction dependent ones.
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With typical SS amps I largely disagree with the idea that speakers and amplifier need to be considered together, and of any synergy etc here. It is of course though a very grey area! Most "straight wire with gain" amps achieve very low distortion from very high NFB and this endows them with extremely low output impedance and hence negligible interaction with speaker impedance variations. The majority of mass market SS amps are of this generic type...

Obviously with SET's it becomes very important indeed and with even many push pull valve amps with overall feedback the output impedance will likely be high enough to show at least some interaction with speaker impedance variations... Much depends then on what we consider to be the typical amplifier!

The science behind how to get almost perfect measured performance is of course well understood but as to why an amplifier with 0.001% THD, FR of 1Hz - 100KHz and damping factor of 300, which should for all intents and purposes be that "straight wire with gain", perfect amplifier, actually sounds "forced", "grey" and lacking depth perspective whilst another of either similar or even quite disparate measured performance sounds effortless and open is I suggest very much still a mystery!
 
Arkless Electronics said:
The science behind how to get almost perfect measured performance is of course well understood but as to why an amplifier with 0.001% THD, FR of 1Hz - 100KHz and damping factor of 300, which should for all intents and purposes be that "straight wire with gain", perfect amplifier, actually sounds "forced", "grey" and lacking depth perspective whilst another of either similar or even quite disparate measured performance sounds effortless and open is I suggest very much still a mystery!
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OMG:rolleyes:
 
Arkless Electronics said:
With typical SS amps I largely disagree with the idea that speakers and amplifier need to be considered together, and of any synergy etc here. It is of course though a very grey area! Most "straight wire with gain" amps achieve very low distortion from very high NFB and this endows them with extremely low output impedance and hence negligible interaction with speaker impedance variations. The majority of mass market SS amps are of this generic type...
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Yes. The snag is when a speaker has neither a flat frequency/time response and an input impedance that isn't the same resistance across the band. Given the real world variations of speakers that can mean that a driving impedance variation with frequency will alter the sound for the better. Lottery if you don't know all the relevant details.

The avantage of a flat amp that can drive anything via a near-zero output impedance is that someone *could* then experiment with an interposed network to achieve the same result. But of course, almost no-one does, and it never occurs to reviewers to mention a point that might put them out of a job. 8-]
 
Jim Audiomisc said:
Yes. The snag is when a speaker has neither a flat frequency/time response and an input impedance that isn't the same resistance across the band. Given the real world variations of speakers that can mean that a driving impedance variation with frequency will alter the sound for the better. Lottery if you don't know all the relevant details.

The avantage of a flat amp that can drive anything via a near-zero output impedance is that someone *could* then experiment with an interposed network to achieve the same result. But of course, almost no-one does, and it never occurs to reviewers to mention a point that might put them out of a job. 8-]
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Confusingly I'm reading that as you first agreeing with me... then saying the opposite.. and then agreeing again:confused:

"when a speaker has neither a flat frequency/time response and an input impedance that isn't the same resistance across the band. Given the real world variations of speakers that can mean that a driving impedance variation with frequency will alter the sound for the better. Lottery if you don't know all the relevant details."

I'm saying that this is precisely what we can avoid by using a high feedback SS amp of low output impedance. Whatever other qualities such an amp brings to the table is another matter!

The use of amplifiers which are not a zero impedance "straight wire with gain" to voice speakers would certainly make things a lottery! This should be avoided at all costs IMHO! If a speaker designer uses some SET to audition a speaker he is developing and to voice it then it will likely sound wrong with any other make and model of amp!

It may well be that certain vintage speakers which some say only sound right with an old valve amp are showing just such an issue.

If OTOH he uses a big SS amp then it should sound correct with virtually any SS amplifier with high feedback, ie the vast majority of mass market amps.
 
That makes me think of a picture Tony found where Jim Rogers seems to be using a NAP 120 with JR 149s. I’m now wondering whether I need to try one.
 
All the above indicates it’s a good idea to use amps and speakers from the same maker, with the amps specifically designed to drive the speakers, like I did :)
 
Arkless Electronics said:
Confusingly I'm reading that as you first agreeing with me... then saying the opposite.. and then agreeing again:confused:
.
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My point is that for some people with some speakers they will have good reasons to *prefer* a specific amp *because* it's output impedance isn't essentially zero. i.e. *because* of the interaction which ensuring a near-zero output impedance removes!

They are using one 'imperfection' to adjust for another.

The problem is that without a lot of specific data, this is a matter of 'luck' and will seem mysterious to others. And can mean 'recommendations' that can mislead.
 
Jim Audiomisc said:
My point is that for some people with some speakers they will have good reasons to *prefer* a specific amp *because* it's output impedance isn't essentially zero. i.e. *because* of the interaction which ensuring a near-zero output impedance removes!

They are using one 'imperfection' to adjust for another.

The problem is that without a lot of specific data, this is a matter of 'luck' and will seem mysterious to others. And can mean 'recommendations' that can mislead.
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Semantic confusions apart we're reading from the same hymn book then:)

The vast majority of amps in most common use eg Exposure, Quad, Audiolab, Rega, all the main Japanese brands etc are high feedback SS amps and therefore have a low output impedance and can be expected to at least get frequency response/tonal balance right with just about any speaker that has been designed/voiced with a low impedance SS amp... and as you say when used with an amp which has high output impedance such as an SET it's a lottery as to what the result will be and some may even prefer the non flat frequency response that results.
 
I've been building high efficiency speakers for the best part of 25 years, I've always found it easy to integrate loudspeakers with single ended amps, I'd guess it because I use very efficient drivers where there's a large element of self damping in the drivers, and where I can, I choose drivers with an 'flat as I can' impedance and response
Like you say it can be a lottery, but I'm my case its proved to be all about the drivers and I've found it easy to get a good sound.

I'm sure you have heard my system at one of Steve's nebo's I've been to a couple so far.
..large open baffles,
dont think my latest red and black (ported) box like open baffles have had an outing there (yet )
 
I never get this level matching argument when auditioning amps. Maybe if you're doing a quick A/B in a shop, but that's the worst way to demo stuff.
Better is to have it a home for a few days or buy 2nd hand and demo at will over an extended period and pass on if you don't like it and minimal loss. Most amps will sound different at different volumes too, so level matching would only provide one reference point - if you like your music loud and the chosen amp sounds worse at higher volumes than your matched level demo then that demo was worthless.
 
mandryka said:
Thanks. I found an internet discussion which said that Denon POA 6600 and 4400 implement dynamic bias - there are a couple for sale on eBay at the moment in fact, but I couldn’t see any comments on the sound or the quality of the amps themselves.

Did you make your own current dumping amps, or have you found a Quad amp you like? Or does someone else commercially use current dumping?
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Google will get you reviews of the Denon. I made my own, it’s based on the Quad 405 with mods from someone else and some from me, it’s in the DIY section but it’s not a beginners project.
 
Rana said:
Hi Colombo, for me it started after I bought Decware ERR speakers a few year's back (I was firmly in the "choose your system around your speaker" camp in those days, and still am to a major extent), they revealed very clear differences in detail and presentation in amps such that I went through numerous brands and types and became a real amp swapper for a while. I ultimately decided that juicy SS amps worked best for my ears despite my Decware speakers being designed for flea-powered valves and that I listened at low/moderate volumes. I have since settled on Linx and AudioNet amps powering (even more) revealing MC Audio RL21s in both my systems.
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Interesting, thanks.

I wonder if it's an inherent nature of different speakers? Some reveal amp differences but others create such such a homogenised sound that render any amp characteristics null?

From what I understand LS50 are quite revealing of amp differences but never had the chance to find out for myself.
 
Steve 57 said:
Single ended is where the signal is amplified through a single transistor or valve, the music waveform stays in one piece. All single ended amps are class a.

most amplifiers are push pull where the positive and negative parts of the signal ( think in and out of the speaker cone )are split with one device amplifying the positive and the other amplifying the negative. The idea is that both sides match, and the waveform retains its original shape, but alot of things have to be right for that to happen, the advantage is that you can get alot more watts out of a push pull pair,

in push pull there are different classes, a ab b c.. in simple terms its just different spacing of the two halves of the signal wider apart to get more volume.. if you can understand that you will start to understand the quality relationship to different classes of amplifier
Hope that makes sense.
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Makes perfect sense, thanks very much
 
OldSkool said:
I never get this level matching argument when auditioning amps. Maybe if you're doing a quick A/B in a shop, but that's the worst way to demo stuff.
Better is to have it a home for a few days or buy 2nd hand and demo at will over an extended period and pass on if you don't like it and minimal loss. Most amps will sound different at different volumes too, so level matching would only provide one reference point - if you like your music loud and the chosen amp sounds worse at higher volumes than your matched level demo then that demo was worthless.
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The feels like a really good point (esp as I'm after an amp that performs at lower to moderate listening levels)
 
Arkless Electronics said:
Semantic confusions apart we're reading from the same hymn book then:)

The vast majority of amps in most common use eg Exposure, Quad, Audiolab, Rega, all the main Japanese brands etc are high feedback SS amps and therefore have a low output impedance and can be expected to at least get frequency response/tonal balance right with just about any speaker that has been designed/voiced with a low impedance SS amp... and as you say when used with an amp which has high output impedance such as an SET it's a lottery as to what the result will be and some may even prefer the non flat frequency response that results.
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Mostly yes. However you have to watch out for quirks like the way the use of an output capacitor in the older single-ended designs will interact with speaker inductance at LF. QUAD 303 + ESL57 being the prime example. Chances are that PJW developed these to go together - albeit via a similar effect with the QUAD valve amps. One of those questions I didn't get to ask before it was too late!

Note that - depending on the amp and speaker and room - the SET interaction, etc, may result in a 'flatter' response at the ears! The snag being these variables won't be the same for someone else in another room.
 
Columbo said:
Interesting, thanks.

I wonder if it's an inherent nature of different speakers? Some reveal amp differences but others create such such a homogenised sound that render any amp characteristics null?

From what I understand LS50 are quite revealing of amp differences but never had the chance to find out for myself.
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You can expect a difference between speakers that have an impedance/frequency plot that mimics the Alps from one that mimic a billiards table. 8-]
 
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