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In Reply to: Re: Maybe it helps, but I doubt it can alter DSP algorithms... posted by Jack G on August 22, 2004 at 07:07:33:
I heard the commercial Evo2 amp on an excellent setup. I played with the 2x20W demo kit from Tripath (including battery powered). I had the opportunity to listen to many examples of these amps at Tripath demo room (which is quite impressive!). I also talked with a person from Tripath, who's familiar with what those chips do. It confirmed to me what I was hearing.
I'll admit that the "artifacts" are at very low level, but they're there. You just can't hide what's there!
As for analog amps, some do have considerable noise, but it's not the noise LEVEL that bothers me. I can listen to an amp with considerable hum and enjoy every minute of it (but it won't be my first choice either...)
What really bothers me is what the digital amps do to TONE when playing at low levels. This is a different kind of distortion, and to my ears worse than IM (i.e., mixing products). Maybe this is a subjective statement. I listen to extremely low level nuances. For me, harmonic structure is what makes the music "complete" and realistic, and those natural harmonics are at levels close to the noise floor.
My ear and brain can tell hum from harmonics but have a tough time coping with pseudo-random noise that's not "white noise" in nature.
There are many so-called "high-end" analog amps which I can't live with, because they come across too "clinical" or too euphonic. That's not music for me.
Can I live with an Evo or the Panasonic? Probably so, but neither would be my first choice!
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Follow Ups:
when the Evo4 is run in bridged mode you have double the Evo2 processing power, 2 tripath chips in place of the one in the Evo2... my understanding is that each doubling of a processor results in a 3db reduction of "computation noise"... Accuphase used to have a brute force implementation where they had something like 8 (or was it 16) Burr brown DAC chips per channel... with the right preamp you could, potentially, run an Evo4 as a monoblock with a hyper bridged configuration and gain an extra 3 db in the process.Another thing to consider is that while chips are information processing systems, they are physical systems too. Some of that low level grunge may be the result of the chip's own self exitation as it converts an analog audio signal into radio frequency pulses. I believe those fine vibrations contribute to the chip's overall sonics. With the RF-57 tuning buttons in place, both the resolution of low level information and the quality of it was markedly improved. I was hearing little wispy tones and nuances that simply weren't there in the stock amp. I also noticed that as the amp played for a while this quality of "organicity" would improve to the point where I wasn't thinking about amplifiers or hardware....
Unless bridged systems are very well balanced, they'll add up their noise. That noise is a product of the algorithms that were built into the design and no vibration control will reduce those.
But the chip and board vibrations may be reduced, obviously.
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"What really bothers me is what the digital amps do to TONE when playing at low levels. "You are lumping every Class D amplifier into the same group. I will imagine, that ICE, TI, Sony, Sharp,Yamaha, Tripath etc all have different signatures. Your brush seems rather broad, as the implementations are very different and it unlikely that their tonal signature will be similar accross the board.
I agree that the sonic signatures would be slightly different, due to differences in processing. However, all digital technologies share common problems, like clock jitter. They are no different in that regard from DACs. Some people are more sensitive to such distortions, some people less.
The bottom line is really the issue of your priorities. If you values dynamics as the most important aspect of realistic sound reproduction then the excellent efficiency and seemingly infinite power reserves of digital amps just cannot be matched.
I'll admit that I'm willing to sacrifice loudness and bass slam for the utmost tonal neutrality and coherency (by way of excellent instrument separation). My preferences limit me to small amps (just a reality, not a law of nature) and reasonably efficient speakers (and not necessarily horns). I hear sonic degradation (in long term listening) from amps with with parallel devices and bridged or push-pull configurations. Some people don't - or don't care.
Similarly for digital artifacts. Just different trade-offs!
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My analog ICE loaded H2O monos, powering 1 ohm Scintillas, produce a music scene that equals the ear's ability to discern instrument separation. I can literally hear the individual violins in an orchestral violin section. Each instrument maintains correct tonality, micro inflections, macro dynamics, and relative size plus placement at all times.
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> > However, all digital technologies share common problems, like clock jitter. < < <
Agreed, but jitter is easily addressable-its been known about and dealt with for a long time now. Out of curiosity, do you have the Jitter measurements of any of the digital amps?> > > The bottom line is really the issue of your priorities. If you values dynamics as the most important aspect of realistic sound reproduction then the excellent efficiency and seemingly infinite power reserves of digital amps just cannot be matched < < <
With speakers that are 100db efficient, the last thing I needed was a seamingly infinite power reserve. I can get that with 20 watts. There are always trade offs, and I certainly agree that everyone has different sonic priorities, but I'm not sure I agree with that assesment. I had great dynamics with my SETs, and I don't really consider that one of the eVos better sonic traits. The eVo was a step up in neutrality, tone. timbre and harmonic structure.> > > I'll admit that I'm willing to sacrifice loudness and bass slam for the utmost tonal neutrality and coherency < < <
As will I, though I suspect we may have different defintions of coherency-possibly neutrality too. Either that or we hear differently.> > > hear sonic degradation (in long term listening) from amps with with parallel devices and bridged or push-pull configurations. < < <
As a *gereneral* rule, so do I.
As you say, there are always trade offs, and we all must choose what serves our needs the best.
enjoy,
Jack
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Yes, I bet we hear slightly differently.
As for jitter, I can hear it in somewhat imprecise positioning and size. The amps don't suffer as much from the jitter as DACs, maybe because they constantly vary the operating frequency. The one-bit DACs are the most sensitive to jitter, which affects a partial sample.
It will be complicated to measure jitter directly when the operating frequency varies all the time at an unknown rate...
Perhaps it can be related to the variation in harmonic distortion on a fixed tone. Maybe we have to ask the source!
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"As for jitter, I can hear it in somewhat imprecise positioning and size"thanks for further clarification on the subject, the digital amplifier I own definitely does not suffer for this artifact rather one of its stand out qualities precise positioning and image size, it rendition of chimes and such like is very good, tonally accurate and precise positioning within soundstage. just my observations.
I am not sure I agree on the instrument separation and tonal neutrality, but thanks for the clarification anyway.
I would expect different digital amps to sound quite different-even different tripath or ICE etc. to sound different.I find the tone of the eVo to be quite consistant despite volume.
As for the "grunge" at low levels, it would not surprise me if different tchnologies have their own distortions-in fact I would almost expect it. That said, they don't seem to bother me-perhaps because I have lots of vibe control, which seems required.
Jack
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