Do Amplifiers Sound Different?

[whoaru99]

Nice Stuff.....

Thank you.

[Arneson]

Wow, OK, so that's it. Nice ending " Thank You ".

[Karma]

HI All,
I think this may have been the most amazing thread I have ever seen.

Sparky

[David Meek]

It's definitely had its moments, and then it's had some "moments". :takecover:

[Russ L]

Great topic but I've said my piece. I'm done! I'm retiring from this thread :later: -Russ

[wolfgang]

This is thread has been educational. After following it for a while it occur to me that when most audiophiles object to 'blind' listenings they do so by autopilot without ever trying to understand what it is all about. They are also those who have not actually had any first hand experience how it could be done.

[misterdoggy]

Oh oh here we go again......

[Aussie Geoff]

Wolfgang,

I agree... Indeed when I am trying a new component out, if possible (and it isn't always) I try and do my own blind testing by getting my wife / son or the salesman (if in store) to switch between them without telling me which is which. That way my notes / impressions of the sound are not influenced by any feelings about new cable / CD player etc as much. I am often surprised by this in terms of what sounds good or what the sound differences are.

The other technique I'll do is swap components and get my wife and son to describe the difference they hear.. Again without telling them which is which...

I am quite selective about what I listen to this way and often the highly rated component that I liked when demoed by an enthusiastic salesperson and thought had some big difference etc, can only have minor changes (or no) when compared this way (fooled by the glamour of the item I guess). Equally though there are components where the differences are clear to me, my wife and son. For example amplifiers that sound better even when at a lower volume than the ‘competition’... I now try and limit what I buy to this type of component - those with a clear audible step-up from what I have even when I don't know which I am listening to! True value for money (for my families ears and budget anyway)

Highly recommended...

Geoff

[Bob]

What is this numbers you keep refering to?

Specs., usually put out by the manufacturer.

Here are three examples of specs. on amps that I have owned. Based on the specs. What can someone tell me about how the amps sound, and which should I have kept?
Unless you believe that all amps sound the same. Then the only thing would be price.


Amp 1
Frequency Response
1 Hz-80kHz
RMS @ 4 Ohms
1200 W
RMS @ 8 Ohms
600 W
THD
0.5%

Amp 2
Frequency Response
.3Hz-250kHz
RMS@ 4 Ohms
450 W
RMS @ 8 Ohms
225 W
THD
<1.25%

Amp 3
Frequency Response
.5 Hz- 240 kHz
RMS @ 4 Ohms
Not available
RMS @ 8 Ohms
200 W
THD
0.5%

[autio]

Amp1 would definitely sound the best with tibetan chants lending a slightly exotic flavor to the music that only those with tin ears would not enjoy.

Amp2 With its ultra wide frequency response would best serve in a lumber yard or warehouse powering up tranducers specifically designed to keep the european starling and north american robin from building nests.

Amp3 most likely this amp is a pure class A design That probably doesnt sound as good as its designers had hoped. Looking deep into the specs leads me to believe that it is a "concept amp" that never got put into full production and this one off copy is used to heat up a small bathroom on cold winter mornings. :W

[Gump]

Amp1 would definitely sound the best with tibetan chants lending a slightly exotic flavor to the music that only those with tin ears would not enjoy.

Amp2 With its ultra wide frequency response would best serve in a lumber yard or warehouse powering up tranducers specifically designed to keep the european starling and north american robin from building nests.

Amp3 most likely this amp is a pure class A design That probably doesnt sound as good as its designers had hoped. Looking deep into the specs leads me to believe that it is a "concept amp" that never got put into full production and this one off copy is used to heat up a small bathroom on cold winter mornings. :W

Nice shot autio....funny!! :rofl:

[AptosJeff]

Tha was good, autio.
I would not put much stock in specs, except maybe to get an idea of how much power it has. I would pay attention to general configuration such as transistor, tube, class A, monobloc, etc.

[wolfgang]

I agree...

No. No. No. If you agree with everything I said then how could we prolong this thread into a endless debate. Lets try again.

So that what's you meant by numbers. I don't remember anyone in this thread ever suggest one could guess how any amps sound like from the spec. However, a lot of people did appear to suggest that the numbers on price tag do.

[bigburner]

Now that we're approaching the group hug phase of the debate I'd just like to remind everyone about my 'diamond eyes' which enable me to identify a voiced amp simply by looking at it. Furthermore I'm prepared to undergo a double blind test to prove it!

[Briz vegas]

bigburner - do you think us silly. You don't mean a double blind test, you mean a double deaf test to prove that you are not cheating by using your ears.

[whoaru99]

Man, now it's really getting deep!! :lol:

[Victor]

Although I am late to the party, - I would like to make a few comments. Many people think that a Power Amplifier design is an art form, - this is not true. When one describes an amplifier or its sound in terms of transparency, fluidity, dimensionality, etc, one attributes the qualities relevant to an artistic expression to an entity that has no built in art of any kind.

A power amplifier contains electronic components that do not produce any sound. In fact, sound generation is not a purpose of an amplifier. Power Amplifier’s function is to simply hand over an electrical signal from a low-power source to a mechanical transducer capable of producing sound pressure with the spectral content identical to the low power source. One can think of a Power Amplifier as an interface or, as analogy would have it, a microscope that amplifies the image without distorting it.

In other words, the only difference between what goes into a Power Amplifier and what comes out must be a power content of the signal and NOT its spectral content.

If a Power Amplifier changes this spectral content then you are going to hear material that the sound engineer did not record.

Well, - considering the above argument I certainly would not want any amps of mine, and I have many, to have any sound. And if they do, then any investment in my speakers has not been justified.

regards,
Victor

[bigburner]

In other words, the only difference between what goes into a Power Amplifier and what comes out must be a power content of the signal and NOT its spectral content.

Victor, does the same apply to audio preamplifiers?

Nigel.

[audioqueso]

My 2 cents.

- I received my B&W 805s.

- I purchased two Rotel amps, and found that the 805s sounded good with soft music, but sounded too laid back with rock/hip-hop music with the Rotel.

- I purchased a Parasound amp, and found that the 805s sounded good with soft music, and now shine just as well as the 700 series do with rock/hip-hop.

So yes, they do sound different.

[Victor]

Victor, does the same apply to audio preamplifiers?

Nigel.

Yes it does...and to a larger degree.

[Victor]

My 2 cents.

- I received my B&W 805s.

- I purchased two Rotel amps, and found that the 805s sounded good with soft music, but sounded too laid back with rock/hip-hop music with the Rotel.

- I purchased a Parasound amp, and found that the 805s sounded good with soft music, and now shine just as well as the 700 series do with rock/hip-hop.

So yes, they do sound different.

I do not doubt your experience. I am sure you heard difference in sound. Both, - the Parasound amp and the Rotel product you have are well designed units. However, why point the finger at the amps? Perhaps there are other ‘dark forces’ at play here?

As I mentioned before, amplifiers do not qualify as an art objects. You can never describe them in terms of “soft” sounding. You can never say that one amp sounds better with rock and the other sounds better with classical music. If you perceive those differences then there is a rational explanation to your experience and I guarantee you it has nothing to do with well-designed amps, - at least not with Rotel or Parasound.

In order to convince yourself that you would have been satisfied with either of those amps you need to conduct your test under the controlled conditions. Otherwise, you are introducing variables into this equation that would persuade you to prefer one amp today and the other amp tomorrow.

Victor

[misterdoggy]

Excuse me,

But yes the Amplifier can make a difference and Yes when he switched Amps he heard a difference.

If he said he did, then we have to accept his 1st hand experience and ability to hear a difference. There could be plenty of other Causes as well.

If you look below at the Rotel 1080 stereo Amplifier 2 x 200 watts (a very good amplifier don't get me wrong) and next to it the 2 Mark Levinson 33H Monaural Amplifiers delivering 150 watts per channel, I can promise you for $25k for the pair you will "hear the audio gospel" Hallalujah !!!

[Victor]

misterdoggy,

I just love the looks of those Levinsons, - great picture!

Now, - I did agree that audioqueso heard the difference in sound. I do not dispute his perceptions, nor will I question his experiences. I simply point out that those perceptions and experiences have nothing to do with power amplifiers in question, and they have everything to do with the way he conducted his test.

I know those Levinson’s quite well. They are very good amps. I heard them in action many times. However, unless you are driving a pair of Apogee Scintillas you will have an impossible task justifying the use of those $25k boxes. Even then, - there are many alternatives that will put those Levinson’s to shame.

Other then the name and the fame those Levinsons have nothing to offer these days. There is absolutely nothing in the engineering of those Levinsons that justifies their price. Certainly you do not need them to power up any set of speakers that you can purchase today even if you spend $50K on a pair.

All in all there are much better designs on the market today for a quarter of the price.

Victor

[nbourbaki]

I'm a little confused as to how 5 guys in a room performing a double blind test is statistically significant or that anyone could draw a scientific conclusion from such an activity. To be valid statistically, I would think you would need hundreds if not thousands of participants.

I'm also a little puzzled with level matching in such a test. I bought a powerful amplifier that can pump out significant bass. If all you test is the low water mark of performance between two amps what have your learned? That within a very narrow scope of performance that most people can't tell the difference?

[Victor]

nbourbaki,

It is not so much the number of people that is important; - it is the consistency of the results that is important. One can make a determination of how many people should participate to represent statistically correct population sample. However, even in your example the test will hold true for the population sample of much larger then 5 people.

Well, - if the participants pick one amplifier over the other 8 times out of 10, - this in itself does not, statistically speaking, constitute anything more then a simple guessing, although on the surface it may sound significant.

My experience has been such that people would pick one amp over the other 6 times out 10 on average, - in other words it is always a nearly 50-50 split, - that tells you that no significant difference is ever heard under the controlled conditions with properly set-up testing procedure. By the way, I participated in tests with more then 20 people involved, some were musicians with conservatory education, while comparing $25K+ amps with $200 receivers.

Victor

[whoaru99]

I'm also a little puzzled with level matching in such a test. I bought a powerful amplifier that can pump out significant bass. If all you test is the low water mark of performance between two amps what have your learned? That within a very narrow scope of performance that most people can't tell the difference?

We're not talking about the crankability factor, we're talking about the "sound" of the amp.

Level matching to gauge the actual sound quality (vs. loudness) is critical because most people inherently choose the louder test as sounding better.

If an amp sounds good at low volume, should it not sound like more of the same as the volume is increased within the limits of the amp?

[Brandon B]

So then , I A/Bed a new UcD amp I got for my surround channels with the Odyssey Stratos I have running my front speakers, and definitely heard different character in the treble. Switched back and forth a couple of times.

I had to use different ICs as the UcD amp is hooked up with some RCA to XLR cables I made, and the Stratos was connected with RCA-RCA outlaw cables.

So since the amps sonic signature must be identical, these two IC's must be coloring the sound differently, right? In which case all cables don't sound the same. Hmm. The amps have cable in them.

BB

[Victor]

Brandon,

There are a few things to keep in mind here; - the UcD amp module is a switching amp, while the Odyssey Stratos is a conventional linear design. Switching amplifier in general will have an inferior distortion and noise characteristics. Although the UcD is one of the best designs out there, still its THD+N may not be below audibility. Still, I doubt that it is all that audible. Again, in order for you to conclude anything at all, your test must be properly set-up; - clearly you did not do that.

In general the interconnects do not contribute to any perceived sound, unless they are defective or used inappropriately. Also, the cables inside most amps are plain vanilla 16 gauge.

Victor

[whoaru99]

So then , I A/Bed a new UcD amp I got for my surround channels with the Odyssey Stratos I have running my front speakers, and definitely heard different character in the treble. Switched back and forth a couple of times.

I had to use different ICs as the UcD amp is hooked up with some RCA to XLR cables I made, and the Stratos was connected with RCA-RCA outlaw cables.

So since the amps sonic signature must be identical, these two IC's must be coloring the sound differently, right? In which case all cables don't sound the same. Hmm. The amps have cable in them.

BB

Good try! :T

It's easy to argue a point on the side that cannot be positively disproven.

Current estimates put the world population at something just over 6.5 billion people. If we could ABX test all but one, there is some possibility that one untested person could pass the test. But, what are the odds, and where does one draw the line that reasonable measures have been taken to arrive at a conclusion?

[AptosJeff]

Victor,

Thanks for the insights. You have some interesting opinions on amps. If I understand you, I would summarize as follows:

1. Subjective terms do not apply to power amps.
2. A power amp does not affect the sound.
3. A power amp should not affect the spectrum, and if it does, you will hear something unintended.
4. If power amps do affect the sound, there is no use investing (a lot?) of money in speakers.
5. Well designed amps (including Rotel and Parasound) cannot be described in subjective terms.
6. Switching amps generally have inferior distortion and noise characteristics than linear amps and this may be audible.

It seems you are saying that ideally, amps should not affect the sound, and while some do, the well designed ones don't. Well, I wouldn't disagree with that much, but what is a "well designed" amp? I believe many of us do hear differences in some of the amps you mention, and certainly many of the amps we use. So I would say that most amps we are talking about in the forum don't meet your definition of "well designed".

BTW, are you a designer of power amps? What are some the important issues in your mind for a good design?

[Brandon B]

Brandon,

There are a few things to keep in mind here; - the UcD amp module is a switching amp, while the Odyssey Stratos is a conventional linear design. Switching amplifier in general will have an inferior distortion and noise characteristics. Although the UcD is one of the best designs out there, still its THD+N may not be below audibility. Still, I doubt that it is all that audible. Again, in order for you to conclude anything at all, your test must be properly set-up; - clearly you did not do that.

In general the interconnects do not contribute to any perceived sound, unless they are defective or used inappropriately. Also, the cables inside most amps are plain vanilla 16 gauge.

Victor

To be sure, it was a quite unscientific test. However, you made the assumption I was curous to see if anyone made. The UcD amp sounded a bit cleaner than the Odyssey, not the other way around.

Whoaru - wasn't really arguing either way. Just listened to both amps with the same SACD several times. Only other change in the system was the interconnects, so I was basically being a bit of a smart ass. I actually think they had no effect on what I heard.

On an objective level, I agree it's unlikely people could pick one amp out in a test. But I listened to these two for quite a bit at many varying volume levels. There was a different character between the two. And I definitely liked the character of the UcD better.

Now Klaus says his stratos do not like to be switched off, and I did not give the stratos the 2-3 days of warmup time when I had to switch it off to move the speaker cables, so that could very likely be the culprit.

There was also a very marked difference when I got the stratos several years ago to replace an old Alesis RA100, but that is easier to understand as it was straining quite a bit to run the Magnepan MMGs I was using, and was unable to produce much bass out of them.

BB

[bigburner]

Ah misterdoggy, Cinderella and the ugly stepsisters! That Rotel is a little beauty isn't she?

[bigburner]

Originally Posted by bigburner
Victor, does the same apply to audio preamplifiers?

Yes it does...and to a larger degree.

So Victor, now that you're on a roll, does the same apply to CD players and DAC's?

Nigel.

[Snap]

ahhh what a soap opera. I cannot believe I am even jumping in this thing.... but hey why not! :B

This is such a subjective hobby. Well my speakers are better than yours. My amp sounds better than your amp! and the list goes on.

In MY MIND..... it is all subjective! Do I have personal pref about the issue. You bet! I admit that I have more experience with Pro Audio as far as separates and different amps are concerned. To me...... and I would like to stress that it is my thoughts, MY EARS. I "THINK" I can hear a diff between a cheap 200W QSC and a Not so cheap 200W QSC amp. But that is just me. I have been fooled before. My brother did it to me. Did not let me see the amp rack at a church, and played a CD. Then he faded it out, switched some things.... Played it again and I picked the cheaper amp to sound better! I have also done it and I could not tell the difference between the 2.

Here is the bottom line. As long as THE OWNER of said system is happy with the system than that is ALL and I do mean ALL that matters. I have had people SWARE up and down that the Jamo Sat system sounds as good as the Totem Rain Makers! And that the RXV-459 sounds just as good as the RXV-2600! 8O OK fine.... who am I to argue with them! So it is an RXV-459 and a set of Jamo Sat speakers. Coming up!

Unless the owner hears for himself the difference than nothing any of us say is going to change his mind!

I learned a valuable lesson from a customer the other day..... He was looking at the difference between HDTV and 480i. He said and I quote....

"Yes it is a better picture, but it is NOT $2500 better!" And you know to him it was not. So he stuck with his Sony 36 inch CRT and got the rest of the system. And he is happy as all get out and sending more people to me as a result.

There have been a lot of good info that was passed in this thread. You had to get through the "As the Turn Table Turns" portion..... but a lot of it was good reading!

To sum it up.

1. All that matters is if the owner of the system is happy.
2. Unless you can prove with THEIR EARS that the amps sound better or worse, our words and post are not going to do it.
3. And everyone's system sounds better than the other guys, no matter how much the cost difference is! :B
4. And being HONEST with one self is the hardest person to be honest to. Can you really hear a difference? Or are you trying hard to justify the difference of the $$$$$ you just dropped in the upgrade? (Go back to #1)

[Arneson]

I am the owner of my system, am I happy? Yes and No.
Ha,haha

Very well put Snap, (wonders what other crap you have in house).

[Brandon B]

Yeah, that's the bummer for me. I was happy. I was hoping to hear at worst, equivalence, and at best, that the stratos sounded nicer. Now I have to figure out if I want to try and replace the stratos with a UcD unit.

BB

[Snap]

Very well put Snap, (wonders what other crap you have in house).

Master Bed:
42 inch LG Plasma
Jamo 6.521K4 In Ceiling Surround Speakers. 5.0 in the ceiling.
Jamo 10 inch Powered Sub
RXV-659
DVD 657
Pure AV Power Conditioning
Control 4 HT Controler

Rest of the house:
8 Zones of audio (3 are oustide)
Control 4 Touch Panels
Structured wire with LAN, cable and Phone.
Control 4 T Stat.

20 inch LCD in Master Bath
15 inch LCD in Kitchen

All light switches and fans are Control 4.

10.5 inch Touch Screen Remotes
Media Server
XM Radio Tuner
and some other stuff.

I will try and post some pix some time. All I have taken so far was the Pre-Wire pictures a while ago.

[whoaru99]

Yeah, that's the bummer for me. I was happy. I was hoping to hear at worst, equivalence, and at best, that the stratos sounded nicer. Now I have to figure out if I want to try and replace the stratos with a UcD unit.

BB

Why don't you gather up a friend to help you with a blind, level-matched test to see if you can confirm or refute your own findings as to the sound of the amps?

Nothing to loose besides a bit of time. Actually, the time would not even be a loss because it would be educational one way or the other.

[Brandon B]

Because none of my locally located friends care enough about sound quality to have an opinion I would trust (and few of them I want touching my stuff ). I'd want to do it with more than just my ears as a reference.

And the time is something I don't have any surplus of, at least in the short run. Pulling out my audio rack and swapping connections is a mildly time consuming enterprise, and I have a lot of things I want to do that have been delayed by constant travel to Tokyo and work.

I will be doing further comparison down the road, as I would much rather spend the $1000 or so on something besides another amp, (like a DAC1 or a new projector). We'll see if I can make it a more rigorous comparison. What will we all say if I can spot the difference I think is there under legitimate test conditions?

BB

[Victor]

I would summarize as follows:

1. Subjective terms do not apply to power amps.
2. A power amp does not affect the sound.
3. A power amp should not affect the spectrum, and if it does, you will hear something unintended.
4. If power amps do affect the sound, there is no use investing (a lot?) of money in speakers.
5. Well designed amps (including Rotel and Parasound) cannot be described in subjective terms.
6. Switching amps generally have inferior distortion and noise characteristics than linear amps and this may be audible.

Your summary is fairly accurate. Generally, I do agree with points 1-5.

Your last point regarding switching amps is an open issue. Traditionally PWM amps have in fact displayed inferior noise and distortion characteristics. However, this has been changing. In fact there are linear amps today that actually are worst then some PWM amps in this regard.

It seems you are saying that ideally, amps should not affect the sound, and while some do, the well designed ones don't. Well, I wouldn't disagree with that much, but what is a "well designed" amp?

In a nutshell, a well designed amp might be defined as a linear time invariant system. Linearity would imply that the input only get scaled in magnitude, while the spectrum (frequency) is unchanged. The principle of superposition would also apply here, meaning that all input frequencies are equally treated, - i.e. all get scaled in magnitude. Furthermore, a well designed amp will also be able to deliver a necessary power into the specified load (speaker) at its output without changing the signal spectrum.

Those are somewhat idealistic expectations, since I did not address the distortion issue which in the real world does play a role, but these days a well designed amp will do all of the above with a distortion numbers of less then 0.1% at all frequencies and power levels and into all reasonable loads, which is clearly inaudible. Such an amp can be had today for about $2-5 per watt, no Leninsons or Krells need apply.

I believe many of us do hear differences in some of the amps you mention, and certainly many of the amps we use. So I would say that most amps we are talking about in the forum don't meet your definition of "well designed".

This is not true. Most amps today actually do meet the criteria I outlined above. What you claim you hear has got nothing to do with the amp in question but with the way you conduct your test. Again, under the controlled conditions you will hear no sound from a well designed amplifier, regardless what wire you use or what speakers you use.

There is no magic that hides inside the amplifier box. It is just electronics components that by themselves produce no sound at all, - speakers produce sound. The amplifier can be made out of transistors, vacuum tubes, integrated circuits or whatever the technology might give us, - as long as it meets the criteria of a ‘well-designed amp’ the end result will be the same, - no attributable sound. The physics as we know it today simply does not allow any other form of reasoning.

BTW, are you a designer of power amps?

…not any longer.

[Victor]

So Victor, now that you're on a roll, does the same (input is spectrally identical to the output) apply to CD players and DAC's?

Nigel.

CD player is not as straight forward as a simple power amp. Here we have a conversion process to consider. The digital input and the analog output are not the same signal. It would be more appropriate to say that in the case of a DAC or a CD player, the output must be of the same level of accuracy as the input.

The CD player you have in your house deals with the signal encoded on a CD that has 16-bit precision. Therefore the analog output of this CD player better have the same 16-bit precision. That would mean at least 98 dB of S/N. Very few CD players or DACs can actually claim this, with most giving you 15 bits at best.
So, - applying the above criteria, the conclusion is still the same, - the CD Player, or a DAC, does not produce any sound as long as its output is at 16-bits precision and its frequency response is flat throughout the audible frequency range, - approximately 22-17 kHz. Certainly any tests that I am aware of confirm this.

[audioqueso]

However, why point the finger at the amps? Perhaps there are other ‘dark forces’ at play here?

Because the topic titles asks if different amps sound different. Just giving an answer.

In order to convince yourself that you would have been satisfied with either of those amps you need to conduct your test under the controlled conditions.

No. In order to convince myself, I just let my ears decide if they like the sound or not. The only way to go, or you'll never be happy. :T

[Victor]

No. In order to convince myself, I just let my ears decide if they like the sound or not. The only way to go, or you'll never be happy. :T

I am happy if you happy.

One thing you might want to consider though, - your ears are connected to your brain. And your brain processes the information. You brain is incapable of storing the details of audible data for longer then 20 seconds. It applies to my brain too. Therefore, with no memory to back up the experience as you encounter it, how can your ears determine anything at all?

Simple application of logic would dictate that your ears are at the mercy of your whim, particularly if you try one amplifier today and another amplifier tomorrow.

Would it not be much nicer to get rid of all the variables that can only complicate the issue? Level the playing field, - it is only fair.

Fix the volume to be same using the SPL meter to within 0.1 dB. Do not drive the amps outside their design envelopes. Quickly switch between them while you have no idea which one is connected to the speakers. And then let your ears do the talking…let me know how it goes.

[Arneson]

Y
In a nutshell, a well designed amp might be defined as a linear time invariant system. Linearity would imply that the input only get scaled in magnitude, while the spectrum (frequency) is unchanged. The principle of superposition would also apply here, meaning that all input frequencies are equally treated, - i.e. all get scaled in magnitude. Furthermore, a well designed amp will also be able to deliver a necessary power into the specified load (speaker) at its output without changing the signal spectrum.

I wanted a better understanding of this so here's my attempt at a mathematical proof:
It's like this,

a=x

Add `a` to both sides:

a + a = a + x
Now follow me here...
Combine like terms:

2a = a + x

Subtract `2x` from both sides:

2a - 2x = a +x - 2x
I'm almost getting it...
Combine like terms:

2a - 2x = a - x

Factor out a ‘2′ on the left and ‘1′ on the right:

2 (a-x) = 1 (a - x)
Here comes the truth...
Divide both sides by `(a-x)`:
And Voiala...
2=1

The number 2 amp will sound ampier than 1 .

[audioqueso]

Victor, wow... don't take it the wrong way, but you're thinking way too much into it... unnecessarily! ha ha

Though you have valid points and I do concur with your thinking, one should never listen to your points when deciding between two different amps. Putting way too much thought into it when it should just be your ears that are happy (since that's what this hobby is all about). The question starts off with whether or not amps sound different. Yes, you can bring out the technical difference, but one shouldn't buy audio equipment off of numbers anyways. And yes, if one listened to amp A on Monday, and amp B on Tuesday, one wouldn't be able to remember the exact difference. However, that shouldn't matter anyways since if you take a favorite CD to test on both amps, regardless of what day, one would know which one will sound better to them. Do you disagree? I just think you're putting (and suggesting) way too much thought into something isn't (to our ears). :T