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In Reply to: Re: Hi Paul. You and I e-mailed when I had my ASL 805 SETs for sale. posted by Ralph on December 27, 2006 at 10:10:37:
...talking about Jerry Siegal's comments on A-S equipment?When I saw that you had posted, I hoped you had added something to the SET-v.-OTL question. How about it? How 'bout my transparency v. richness feelings? How about SETs' high 2nd-order harmonic distortion? Is that bad or good?
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Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
Follow Ups:
but I always am dealing with my own biased viewpoint, so you have to keep that in mind.SETs have a richness that OTLs do not have. The reason for this is that SETs have even ordered harmonic distortion that we perceive as richness. The 'lack' of richness found in OTLs is really neutrality.
A proper OTL will be every bit as easy going, in fact more so as OTLs often lack the loudness cues that SETs have. It is these loudness cues BTW that give SETs their apparent dynamic qualities that belie their power output. The loudness cues are odd-ordered harmonics that are masked by the presence of even-ordered harmonics (which plays into the way the human ear hears, so the loudness cues create an illusion). On transients the harmonic distortion will be several orders of magnitude higher than in-between transients; thus the 'dynamic' quality.
Once you are aware of this fact, it is a lot easier to hear the distortion itself when you know what to listen for. Since OTLs can have quite a lot of distortion cancellation (even with no feedback), they often sound more laid back than the best of SETs.
I have found that in 90% of all audiophile conversations, if you substitute 'distortion' for 'dynamics' you get a far more truthful conversation as a result. It is a simple fact that there is far more distortion in reproduced audio than most manufacturers would have you believe, tube or solid state.
Anyway, the other thing about SETs in general is the lack of hysteresis loss in the output transformer that allows them to have the low level detail ('inner detail') that is one of the things that makes them so magical (combined with the lushness of even ordered distortion) compared to push-pull transformer coupled amps.
Take away the OPT and you take with it the argument for SETs; IOW an OTL will have the same or better low level detail, but combined with the greater power, bandwidth and lower distortion of push-pull. Its sort of like having the best of both worlds.
There are several caveats IMO: feedback, pentodes and class of operation other than A will detract from the music and add odd-orders which will be easy to hear with everything else laid bare. That is why we build our amps the way we do- Class A, zero or nearly zero feedback and triode. Those parts of the formula work, as far as I can tell...
I am going to post my thoughts here. I am listening to a pair of A-S OTLs right now, on loan from local dealer.These are the things that occurred to me within the first few moments (I now have 4 hours listening):
1) They sound a bit 'thin' (compared to what I am used to), yet still VERY 'pure'.
2) The bass is astonishing. These are MA-1s run with 4 sets of tubes to simulate 60W M60s. It is far tighter and punchier than my 845 monoblocks.
3) Vocals, for whatever reason, are just not giving me the same tingles of realism.
I have never bought the "yummy 2nd-order harmonics" argument as explaining SETs' realism before because blind listening tests have shown up to 3% 2nd order HD to be inaudible, and no SET is producing that much when mated intelligently to speakers, except on transients. You may be right on the money about the distortion adding to the dynamic effect, but most vocal-only passages are drawing no more than a few watts in typical listening.
I am undoubtedly very conditioned to SET sound at this point. I'm quite open to the possibility that this OTL sound is, in fact, more correct, but I'll be darned if I know how to determine that.
One inescapable conclusion I can offer at this point is that these are fabulous amps. It is truly a unique sound, not like solid-state, or chip-amps, or transformed push-pull tube amps, or SETs. It's another category, and certainly does some things better than all of those.
> > I have never bought the "yummy 2nd-order harmonics" argument as explaining SETs' realismI don't buy the 2ndH argument either and posted some of my own findings in Tube DIY some time back. My own SET design has very low distortion, even 2ndH. In fact most well designed SETs have low distortion at normal listening levels, well under 1% in most cases but certainly under what is commonly accepted for SETs.
Anyway, I experimented with distortion cancellation between driver and OP stage and while I was amazed how great the human ear is at picking minute changes in distortion. Lower distortion sounded sweeter but the thing is, I heard it BEFORE I measured it so it wasn't a case of fooling myself. In fact I only took measurements in an attempt to explain what I was hearing because something initially wasn't adding up. BTW, my measurements were made using a very accurate spectrum analyser with an exceptionally pure signal source.
" I have never bought the "yummy 2nd-order harmonics" argument as explaining SETs' realism before because blind listening tests have shown up to 3% 2nd order HD to be inaudible, and no SET is producing that much when mated intelligently to speakers, except on transients. "It is true that with simple sine waves 2% of even ordered harmonics would be next to inaudible. With a full spectrum of music it is another matter!
What has been shown about even-ordered harmonics is not that we cannot hear them, but that we do not find them *objectionable*. We can definitely hear them- here are some terms that describe even-ordered harmonic distortion in ascending order of distortion present:
warmth
bloom
rich/richness
loose (as in bass)
muddyOne problem with our vernacular is real music has inherent built-in warmth as a function of the way a musician wants it to sound.
This neutrality v. richness issue is a tough one for many of us to get a good handle on. But I keep coming back to the way the SYSTEM sounds--simply more like music with SETs. But I've not heard an A-S OTL in my system!One thing I'm convinced of--SETs seem to have a much-more-linear distortion 'curve' than PP amps, that is, distortion rises more rapidly in the middle of the power band v. a PP amp's very gradual slope and then a sharp increase just before and at clipping. This caused me to buy higher-power SETs than others might have for my 97dB-sensitive speakers. My power indicators PEAK at only a few Watts, leaving my 22-Watters with LOTS of headroom.
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Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
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