traderbam said:
Don't forget
3. The listener has an idea of perfect reproduction which differs from realistisc reproduction.
My point here is something I have said several times before, that unless the music used to judge the equipment has some kind of reference for how it should sound, I cannot see how one could judge objective perfection by listening. That is, I think only acoustic music is meaningful for such objective evaluation. If the instruments are electric from the start and can only be heard via amps and speakers even in concert, then how do we know how it should sound and what is right? For me, reading other peoples listening opinions are only relevant if they have listened to classical mucsic or some other acoustic music, like jazz. Since most people don´t say what they listened to even if asked about it, I find their opinions uselss, at least for me as a classical music listener.
Of course we still don't have an exact reference for how it sounded at the actual recording location from a certain seat in the hall, but if one has been to a lot of concerts, one knows a bit about how the various instruments sound, even if it differs between concert halls.
I agree with your point, Christer, but not with its priority. My experience is that hifi is still so far from realistic that the subtleties you are talking about do not invalidate the listener's judgement.
The scenario I use when someone tells me their hearing is not good enough to judge a hifi system, is to ask them if they could tell the difference between a saxophone solo played on a hifi and a live one in the same room. When you think of it that way, it would be easy to tell. Indeed, if you couldn't tell your partner would send you to your GP for an ear examination. In fact, Linn tried this experiment using a live vocalist and an recording of the same vocalist...even on the best Linn system the blindfolded TV presenter had no trouble whatsoever telling them apart.
The sort of distortions that electronic circuits produce are unnatural and so our brains notice them easily; and hate them. Of course, if you are listening to synthesized music it is hard to tell which distortion is which. But if you are listening to accoustic, then I think it doesn't matter too much about the recording venue and make of instrument and so on, the electronic distortions still dominate our perception of realism.
For example, such perceptions as "edginess", "lack of soundstage", "loss of rhythm and pace", "playing too fast", "loss of emotional expression", are usually electronic problems rather than recording condition problems.
In my opinion, if one could hear a system with no electronic distortion at all it would sound astonishingly realistic.
The scenario I use when someone tells me their hearing is not good enough to judge a hifi system, is to ask them if they could tell the difference between a saxophone solo played on a hifi and a live one in the same room. When you think of it that way, it would be easy to tell. Indeed, if you couldn't tell your partner would send you to your GP for an ear examination. In fact, Linn tried this experiment using a live vocalist and an recording of the same vocalist...even on the best Linn system the blindfolded TV presenter had no trouble whatsoever telling them apart.
The sort of distortions that electronic circuits produce are unnatural and so our brains notice them easily; and hate them. Of course, if you are listening to synthesized music it is hard to tell which distortion is which. But if you are listening to accoustic, then I think it doesn't matter too much about the recording venue and make of instrument and so on, the electronic distortions still dominate our perception of realism.
For example, such perceptions as "edginess", "lack of soundstage", "loss of rhythm and pace", "playing too fast", "loss of emotional expression", are usually electronic problems rather than recording condition problems.
In my opinion, if one could hear a system with no electronic distortion at all it would sound astonishingly realistic.
Traderbam, while I agree we are far from realism, I still think my point matters a lot, at least to me. A very interesting factor is how the acoustics of the concert hall is reproduced, that is, subtle echo effects etc. That is completely missing in most types of music, and unfortunately also in many classical recordings due to close up microphones and mixing. As for instruments, I seem to be very sensitive to the difference between real pianos and digital ones. If the piano sounds digital from the start, then how could I judge if it sounds realistic in a reproduction? OTOH, a grand piano usually does sound lika a grand piano even in old recordings with a lot of noise and distorsion.
Okay, so I guess your comments about "high-bias Class A" versus "low bias Class A" are directed at Nelson, not at me. After reading his note, I found it easy to understand what Nelson meant by those terms, BTW.AndrewT said:
I agree that there can be only One True bias current for a particular Class A topology+output power, but the same OPS can be set at various different bias currents to deliver various levels of power and distortion, hence Nelson's comments, I thought.
tcpip said:
Why? The higher the bias, the more linear the transistors. In theory you can raise the bias as much as you want to lower the distorsion. It may not be very practical, however, to have a bias of 500 A in an amp intenden to produce 5 W output.
The important thing is that as soon as you bias the amp to stay in class A up to clipping levels, you get rid of the crossover distorsion, even if there is still distorsion left that you could lower by even higher bias.
Me too. I am very sensitive to MP3 compression too. I also notice that some very old recordings, sound considerably more realistic than some newer ones. Eg: some Ella Fitzgerald and Louis Armstrong (tube to tape) have had less of the music sucked out of them than most 1980s recordings. Just listen to 1970s Joni Mitchell recordings. Much of this recent loss of quality is due to early transistor circuits and digitization techniques. On Phil Collins' "Hello, I must be going", you can hear which tracks were digitally mastered and which were tape. For a period in the 1980s, Kate Bush refused to record digitally after having been shown its problems by Linn (I think).Christer said:
Fortunately, most current CDs I buy are very well recorded. And, happily, Itunes now provides a lossless compression format.
tcpip said:
Hi,
There seems to be a previous misunderstanding of D.Self.
For Class B/aB/AB crossover distortion is the dominant mechanism.
It is not the only mechanism, but can be the only one that matters.
Class A has no c/o distortion but each stage is not perfectly linear.
As Self shows the input stage driving the Vas creates hf distortion,
3rd order, the Vas ~ constant 2nd order, and the output stage for
class A "wingspread" diagrams are not flat either, mainly 2nd/3rd.
Self has not attempted to identify the limiting areas for class A,
i.e. the relative levels of each stage, but suspects the input.
It should suffice to say it is at a very low level, mainly below
the noise floor except at h.f., it has low high harmonic content,
unlike non - class A, and with standard single pole compensation
a rising distortion with frequency level is inevitable, for the
standard topology this is also true open loop.
Double pole compensation .... for class A ?
/sreten.
I will add to this debate as Dougs name keeps cropping up. The NE5532, the ultimate audio device. Right then SandyK knows what I am talking about. To cut a long story short an audio preamp built with TL072's sounded great, then I used NE5532 for the final version and it was awful. Why ? A particular bar in a piece of music had a Dischord in it that should not be there. I could put the CD on A-B repaeat and keep hearing it. Go back to the TL072 and the Dischord vanished.
The mysteries of audio
SandyK knows what I am talking about. To cut a long story short an audio preamp built with TL072's sounded great, then I used NE5532 for the final version and it was awful. Why ? A particular bar in a piece of music had a Dischord in it that should not be there. I could put the CD on A-B repaeat and keep hearing it. Go back to the TL072 and the Dischord vanished. The mysteries of audio
I don't to wander off the original thread really, but did it suit the TL072 better. Possibly ? It was a peculiar (but all standard OpAmp configurations, modest gains etc) circuit I built around 10 years ago from a design in Wireless World that aimed to recreate a better image on speakers and was based on the work of Alan Blumlien.
Whats your view on the NE5532 or the 5534 Andrew. My Micromega used the NE5534 and I found that even TLO71's subjectively sounded "better" --- a nicer sound to be non technical. I eventually used OPA604's and AD845's and it's brilliant.
Whats your view on the NE5532 or the 5534 Andrew. My Micromega used the NE5534 and I found that even TLO71's subjectively sounded "better" --- a nicer sound to be non technical. I eventually used OPA604's and AD845's and it's brilliant.
Someone invites you to drive your car on a flat test track. They have drawn a yellow line along the track, that looks like a mile long sinewave of constant amplitude and wavelength from far above. All you have to do is keep your speed constant and keep the yellow line at the centre of the car's bonnet. How much you deviate will be measured by computer. You get to try this several times, first at 10mph, then 20mph, then 40mph, then 60mph.
The result is that you managed to track the line very accurately at 10mph. Your total deviation rises with speed, moreso above 20mph, and at 60mph you nearly lost control of your car.
Cross-over distortion is not a feature in this system.
traderbam said:
Yes, I often prefer older recordings, mostly because of the performances, but many have very convincing sound despite techinical shortcomings. I have been in love with the early RCA Living Stereo recordings for a while now. That was before some idiot got the idea to use more than two or at most three microphones. And the haven't tried to remix the original tapes either when reissuing them.
Interesting with Kate Bush. I think she is very demanding about her own recordings, and she is originally played classical piano, I think.
When Glenn Gould did his second recording of the Goldberg variations in 1981 (or maybe 82), the actually used both a digital and an analog tape recorder, since digitial was still quite new and they didn't yet trust the technology. They found that it worked well, however, to record digitally and it was free of noise and fantastic etc., so they used that recording and the analog tape was more or less forgotten. When they made a reissue recently of both his recordings of this work, they decided to also try out the analog version of the second recording. They decided it was in fact better than the digital one that had earlier been used, and decided to use it rather than the digtial one.
AndrewT said:
Hi,
A lot more feedback (up to 30dB) over an extensive high
frequency range compared to single pole compensation.
However the way it is provided can increase
the Vas stages inherent distortion.
(but this is mainly 2nd harmonic, so not a major issue unless
you are after mindless number chasing rather than what
could be described as an optimum distortion profile)
It can exacerbate output stage oscillation problems, (below
the theoretical stability loop frequency), but for overall stability
there should be no issues as long as the loop criteria is met.
It is a common topology for high performance, high frequency
active filters, where open loop gain errors cannot be ignored,
(i.e. the op-amp gain is not "ideal" enough), not used much in
known audio amplifiers, but it works, and it can work very well.
/sreten.- Status
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