I wish I would have come across this before I requested that the other thread be closed. This article restored my faith in this place. Hopefully it will enlighten some of the misguided members on the other thread that were so sure of themselves and vocal enough to derail the conversation with their ill-informed comments. I thought this article might provide some of the objective rationale they were looking for, especially since it is not coming from me.
While the other thread was supposed to focus on the effects of design choices, signal path, etc. it led to a lot of topics that were vigorously and heatedly debated, which is a good thing, but we hit an impasse because many disagreed with pretty much anything
I said. Some of those same topics are addressed in this article by engineers that are
WAY more qualified than anyone else on that other thread. Much of it also coincides with what I was saying.
I actually think that my thinking is more in line with Gene's than it is with many of the
most vocal members of this forum. At times on that other thread I couldn't help but think, does Gene actually believe what these guys are saying? Has this site gone off the deep end? I mean, it was started by an engineer for goodness' sake.
I can't really say I disagree with anything Gene says here or what's written in the article but based on my experience I wouldn't be surprised if many of the individuals on that other thread will disagree and roast and ridicule Gene and the late Julian Hirsch's observations and methodologies.
I'm not looking to re-hash this again and I probably will not even post anything else on this thread. It's a great article and video so I posted it to bring it to the attention of some vocal members that might learn something in case they missed it. You know who you are.
http://www.audioholics.com/audio-amplifier/the-sound-of-an-amplifier
Excerpts:
“So here’s the problem, the people that believe all amplifiers sound the same, it’s usually the people that don’t have a lot of experience designing first of all, it’s the people that may look at textbook and say well the ideal amplifier should have zero output impedance, infinite input impedance, no distortion, no noise – well, show me one, show me the money because I haven’t seen it.”
"You know the argument, in all honesty there's people out there that as long as you don't drive an amplifier past it's linearity, they'll all sound the same. Well, my return to that is to say how do you know whether or not you're driving the amplifier beyond it's linearity? Because amplifier tests are done into a resistive load using a sine wave sweep- OK. Those are very know quantities, very controlled quantities. Well, when you're dealing with a real loudspeaker, a loudspeaker is not a resistor, it's an impedance, it has complex impedance that changes with frequency and some speakers are harder to drive than others."
“If I may give you some anecdotal experiences based on listening tests we have done, many amplifier listening tests we’ve done blind for the people that love blind tests, we’ve done them sighted – sighted meaning you could see the amp but you really couldn’t tell which amp was playing, and we found some interesting results. You know, we’ve had- even at normal levels… and people have been able to identify preferences, you know mostly in the bass range. It’s pretty amazing and there’s been times where I couldn’t really explain it, I measured the amplifiers and they both were high power amplifiers- maybe the amplifier that people preferred had a little bit lower output impedance, maybe it had a little bit lower distortion. So you know it’s hard to say, it’s hard to quantify at what level distortion is audible, how low the output impedance needs to be because it really depends on the interaction of the components. “
“I’ve been testing amplifiers for 15 years and I’m quite surprised that they don’t always bench the way they sound.”
“I’m all about overdesigning rather than trying to design to be the cheapest or design to be the minimum best. I don’t believe in the singularly good minimal best nonsense”
“We’ve measured 8 ohm speakers that have a dip at 2 ohms in the low bass range or even in the upper bass range, what does that do to an amplifier? That sucks life out of amplifiers that don’t have adequate power supplies or adequate output capability from the transistors. So you get a speaker that’s moderately efficient with low impedance with various impedance dips and peaks and if the amplifier itself…has high output impedance or it’s not extremely low output impedance then that can change the frequency response and change the sound”
-Gene DellaSala
Now, from the article a little about Julian Hirsch who for decades has been incorrectly labeled as the father of the - "All Amps Sound The Same" ideology.
“After exhaustive testing of several amplifiers with several different speakers (some known to be “easy” loads and some known to be “difficult” to drive), Hirsch made some interesting observations that simultaneously explained why there were potential sound differences between amplifiers while at the same time remaining utterly faithful to the quantifiable, repeatable scientific process. It remains, in my view, the best explanation for this entire topic that I have yet seen.
Starting with the huge and all-important assumption that the amplifier under test is not being driven into distortion or being operated in a way that could elicit bad behavior, overheating, or engage any protection circuitry, Hirsch found the following:
- Some pre-amp/power amplifier/speaker systems combined in such a way as to produce a very slightly rising or drooping frequency response across the entire 20-20 kHz audible spectrum. It could be a combination of the way the pre-amp and power amp combined on an input/output impedance basis, it could be because of the way a particular amp behaved with the specific load presented by that specific make/model of speaker, but there were system combinations where the frequency response showed a variation across the band.
These were not big variations. Perhaps on the order of + 0.5 dB in the bass to - 0.5 dB in the treble. A 1 dB total tilt, +/-. But over a wide range of frequencies—many octaves—that’s definitely audible. As a matter of fact, this phenomenon is formally known in audio engineering circles as “spectral tilt.” If system “A” is tilted up a dB across the band and system “B” is titled down a dB across the band, experienced listeners will definitely hear that, without question. Godehard Guenther, head of ADS Speakers in the 1970s, talked at length about this effect when voicing his then-top-of-the-line ADS 910 speaker. Extremely slight changes to the speaker’s “tilt” made a dramatic difference in its perceived bass-treble balance and “weight.” Therefore, depending on the program material being used, the interaction of the different components, etc, such a spectral tilt variation could unquestionably lead a listener or reviewer to characterize the amplifier’s sound as “harsh” or “sweet” or “musical,” etc.
- Hirsch also found that small—minute, even—differences in amps’ comparative signal-to-noise ratios often had a tangible impact on their perceived sound.
The SNR difference was not audible as hiss per se. But he did find that a few extra dB of noise could subliminally mix with the program material and lend a very slightly “brighter” or “harder” character to the sound. Granted if amplifier “A” had a SNR ratio of 80 dB and amplifier “B” was 75 dB, both would be considered more than “quiet” enough for high fidelity purposes. But the difference between their SNRs could show up as a perceived difference in tonal character.”
