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Old 13th August 2005, 04:43 AM   #1
LNeilB2 is offline LNeilB2  United States
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Exclamation An interesting thread regarding amplifiers.

http://www.madisound.com/cgi-bin/dis...gi?read=353060

Worth reading.
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Old 13th August 2005, 05:38 AM   #2
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Interesting that one of the posts lists the need of a remote control on a tube amp. I guess ICs are okay for this golden ear bunch when it is convenient?
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Old 13th August 2005, 05:56 AM   #3
LNeilB2 is offline LNeilB2  United States
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That was a preamp question.
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Old 13th August 2005, 06:32 AM   #4
tktran is offline tktran  Australia
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I used to think that most amps sound different, but not to the extent that it could make or break a listening experience. ie. my official stance was that "Yes there's a definite difference, but that's only with A/B switching. In the long term my ears would probably get used to it, so there's no big deal"

It some ways that sat well with me because i wasn't really keen to spend big bucks on amplifier- with an electronic engineering background and having a friend who works at electronics wholesaler, I know that these things cost peanuts to make, there's no new design or R&D to speak of (class A, A/B amps) and I didn't want to spend thousands of dollars just because it was "brushed aircraft aluminium" or "retro-modern" exterior.

But with more experience in equipment and listening, now I really think that with some speakers, the amp can be a make-or-break factor. Perhaps not as important as the acoustics of the room, but there can be extremes- some amp/speaker combination which is unlistenable after about an hour (or having to turn the volume down, when it's not very loud to begin with), and switching amps, and all of a sudden having an involving and emotional musical experience.

I still don't know why or how that happens, and what amps will suit which speakers- it's a real black science/art?

I think double-blinded testing is valuable tool, but we should keep in mind that it's not the be-all-and-end-all of testing. With any kind of test, we have to be careful when judging the results for external validity. That is, just because one can/cannot reliably detect an audible difference in situation A (eg. under some particular controlled test conditions, doesn't necessarily mean the same will hold true for situation B (under relaxed conditions in one's own home.
The same is true for the opposite situation- just because I can hear a difference in in my own home at my own enjoyable volumes doesn't mean I should be be able to detect a perceived difference/better/worse in situation A.

The next leap of faith is that "Well I couldn't hear a difference in a double blind test, so well then must be no difference"

This idea was thrust on me when I studied a bit of statistics at the undergraduate level. The stastical jargon is called "internal validity" - how valid, or correct, a particular test results are; versus "external validity"- given a test with internal validity, the degree to which the results can now be generalised for broader situations or populations. That is, validity is two different things- and given a test which has internal validity, we cannot merely assume that it has external validity.

The other thing with listening is that it's a pretty poorly developed sense. At least in humans. The difference in sound is not imediately apparent, even if there a TRUE difference.
So asking a participant whether he/she can detect for, or prefer some true difference is quite a tough test.

From first hand experience I can say that detecting subtle differences in sounds are much easier when subjects have been are TRAINED- ie. they've heard or know what the differences ought to be.

eg. As a student, it's very hard to discern between sounds heard through a stethoscope. The minute differences in volume and subtle differences in character are next to impossible to discern. Only after being told what they sound like, then it's a bit easier (but even then, not always possible) to discern-

Teacher: "Can you hear that?"
Student: "No"
Teacher: "It's very faint."
Student: "Hmmm"
Teacher: "It's a kind of rustling noise"
Student: (thinking of and listening for leaves in the wind) "Err..."
Teacher: "The kind of sound you get when you touch your hair"
Student: {moves stethoscope to another position to try again}
Teacher: "Hold your breath, you should be able to hear it"
Student: {now feeling very embarrassed} "Oh ok!"

A person who has not been trained to hear the differences will have difficulty detecting subtle differences.

I'm rambling but the short version of my story is that
Being able to hear a difference in a test is not a reliable predictor whether one can hear a difference in an in-home (or other) listening sitation. And whether one can hear a difference in the comfort of their home doesn't mean one will be able to detect it in some kind of test. Drawing conclusions like "There's vey little difference in amps" based on "I couldn't hear it in a double blinded test test sitation" is a false conclusion.The only thing you can conclude is that you couldn't hear it in that particular test"

To detect subtle differences you need training.

YMMV.

regards,
Thanh.
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Old 13th August 2005, 11:33 AM   #5
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I have been designing amplifiers for some 17 years now, and I believe I can make a very good case for the fact that it is far easier to design a specific amplifier for a specific task (or system type) than it is to design the perfect all-round amplifier. For example, I design both valve and transistor amplifiers, and although in a general way the valve amplifier is better (lower distortion, better transients etc.) it will only work better when coupled to a system with the correct driving impedance, which means both D/A converter output impedance and volume control. For this reason it was necessary to design matching D/A + volume solutions for both the valve amp and the transistor amp - although all the equipment will function either way, coupling the correct equipment (in the correct way, using good quality interconnect) will always work better than the wrong way round (especially trying to drive the low-impedance transistor amplifier with the high-impedance valve D/A, for example).

The point I am trying to make is that far too often end-users make all kinds of assumptions about equipment but may be coupling in inappropriate pairings, resulting in substandard setup. Without at least a moderate understanding of the design parameters of given equipment, it is unlikely that you will arrive at appropriate matching by luck. Given this fact, many amplifier or D/A appraisals are not worth much.

Finally, the greater majority of "audiophiles" tend not to understand the importance of certain forms of source material (not only recording quality, but also instrumental content). Therefore, many comparisons are made using source material that does not prove much.
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Old 13th August 2005, 01:12 PM   #6
Zaph is offline Zaph  United States
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Quote:
Originally posted by tktran
I still don't know why or how that happens, and what amps will suit which speakers- it's a real black science/art?
Thanh, I recall you saying that your L18 system sounded better with one amp than the other. That system has a rather large impedance swing right in the midrange. It didn't really affect much with the 3 amps I tested with, but I can't help but wonder if some amps are audibly sensitive to that. (and I mean some solid state amps - I don't design for tubes) So, I've been considering posting an optional compensation network that flattens the impedence curve to almost a straight line. What I'm about to ask may interest you also.

Quote:
Originally posted by clive@tsrg.net
I have been designing amplifiers for some 17 years now...
That makes you just the person to help us out in this discussion. See above and let us know what you think. Note that I'm a member of the "Amps Don't Make Much of a Difference Club" but my ears are open to ideas.
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Old 13th August 2005, 01:20 PM   #7
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The thread at Madisound is the same Great Debate I've been reading, over and over, since 1975. Some people hear valuable differences in the sound of SS amps, some don't.

What bothers me about ABX testing is that it advocates the substitution of an artificial set of circumstances (i.e. a double blind test), for reality. "Reality" is me, listening long-term, to my system, in my room, with my music. If I can hear a difference under those circumstances, then it matters, because it's reality. If I can't hear the same difference in a DBT, the the test is flawed. It's as simple as that.
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Old 13th August 2005, 01:24 PM   #8
Zaph is offline Zaph  United States
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Ps. I took a quick glance at the Madisound thread. I'd just like to mention that Ken Kantor is one of the industry professionals that I respect the most. In fact, the last commercial speaker I ever bought many years ago was an NHT from back when Ken was in charge there.

So it's no surprise that my views almost perfectly match Ken's.
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Old 13th August 2005, 01:51 PM   #9
Mr Evil is offline Mr Evil  United Kingdom
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Quote:
Originally posted by audiobomber
..."Reality" is me, listening long-term, to my system, in my room, with my music. If I can hear a difference under those circumstances, then it matters, because it's reality. If I can't hear the same difference in a DBT, the the test is flawed. It's as simple as that.
You can do double-blind tests in your own home, or under any circumstances you so desire. As long as neither you nor the experimenter know what you are listening to then it is double-blind.

Merely removing the knowledge of what is being listened to will have an impact on the perceived sound. I think it's a shame that there is not serious study done to correlate the appearance of equipment with its perceived sound - it would be most enlightening (I'm sure it would prove that my desire to fill everything with LEDs has a scientific basis!).
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Old 13th August 2005, 02:16 PM   #10
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Just a small addendum. It is unfortunately true - possibly due to economic reality, possibly due to lack of knowledge, maybe other factors too - that the average amplifier out there is quite compromised, and that very often a comparison serves only to compare one unfortunate compromise with another, different one. It is true that there are amplifiers that are much better than certain others, but again this does depend on the system you are hooking them in to.

All this said, the comment above about the 'real test' and personal judgement is very, very valid - if the equipment does not do it for you, in your room, what is the meaning of 'better'?
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