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Old 12th February 2009, 12:57 AM   #21
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I'm just saying that it sounds like a cop-out to say on one hand that they are more accurate but on the other hand that one will only accept one's own listening experiences as evidence of their accuracy, which I hear all the time.>>

Well, it's not a cop out - if I had tons of measurement gear and knew how to use it, I'd gladly do so.

But how do you specifically measure timbre? You can hear it but I don't know how you measure specifically for this. I'd be interested to know.

andy
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Old 12th February 2009, 01:04 AM   #22
SY is offline SY  United States
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You don't measure timbre, you determine if the preamp is audibly altering the signal that goes through it. That's easy to do with a low impedance source and a bypass test. You do need to carefully level match, but that takes nothing more exotic than a good voltmeter. Again, you may LIKE the way your preamp alters the signal, and that's fine if "sounds good" is a design goal for your preamp. But the preamp cannot be called "accurate" if you can hear any difference in a bypass test.
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Old 12th February 2009, 01:07 AM   #23
Salas is offline Salas  Greece
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Originally posted by andyjevans
I must look at the Salas.
andy
Here's the link for you. Nice discussion about timbre by the way.
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Old 12th February 2009, 01:20 AM   #24
Salas is offline Salas  Greece
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Quote:
Originally posted by SY
You don't measure timbre, you determine if the preamp is audibly altering the signal that goes through it. That's easy to do with a low impedance source and a bypass test. You do need to carefully level match, but that takes nothing more exotic than a good voltmeter. Again, you may LIKE the way your preamp alters the signal, and that's fine if "sounds good" is a design goal for your preamp. But the preamp cannot be called "accurate" if you can hear any difference in a bypass test.
Having a goal, i.e. to achieve timbre close to live instruments intimate knowledge, does not mean that it is actually captured like that in the various recordings, and for venues or mic distances that those took place. Of course accuracy to the recording can be less pleasing day in day out for some (most?) people, than approximating some ideal. So I am with SY when looking for the truth. But what is a successful design in general? There is no success reference system or ways to achieve if we don't determine that. To me the answer is: Whatever design meets its predetermined standards is successful. If monitoring is the standard, then we must use criteria of a certain order. If some certain timbre quality always present in the mix is the standard, criteria change.
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Old 12th February 2009, 01:37 AM   #25
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by andyjevans
I believe I'm saying that as far as I can hear, DHTs ARE more accurate in terms of timbre, and are so as a class. I'm not talking about illusion either, like situating speakers in such a way to create a "soundstage".
Please note what I said about accuracy - meaning as SY said, no change from input to output. This is precisely my point - that accuracy (at any point in the chain) and realism of the final product are not the same thing. If in fact DHT's are more accurate, then distortion must be lower. Timbre is nothing mysterious - it's the fundamentals and all the harmonics. If you think it is something magic, then I'll bow out right now.

Like it or not, you are talking about illusion. I don't quite understand why people turn up their noses at this concept. The only thing you can possibly have is, by definition, an illusion.

Quote:
Originally posted by andyjevans
The bit I personally have diffidulty with is that in the recording chain there are God knows how many solid state devices and transformers. So the difficult part is believing that a recording can go through all that lot, and when it encounters a single preamp DHT somewhere in the chain the sound reverts to a more realistic timbre.
You are making my point for me. The preamp (or amplifier), with the rest of the system, doesn't have to be accurate in the absolute sense, it just has to tickle your senses in a way such that you are reminded of the real thing, and your brain does the rest. I don't think that this is a very exotic concept in psycology. Heck, we've all had the experience of a sensory input that triggers very vivid recall. Ever smell something and been transported to a specific recollection? Get the sound close enough (probably in very specific ways) and it will sound "real". Is this necessarily accurate in the objective sense? I don't think so. Does it matter? No, if you are guided by you own ears and you have found what you like. Yes, if you want to understand the mechanisms and want to be able to design for specific outcomes.

I have no problem with your assertion that DHT's do it for you, and IDHT's don't. I do take issue with this statement: "Clearly the preamp stage is critical - it establishes the sound that then gets amplified through the chain. Lose something and it's lost." How do you reconcile that with the above quote about all the devices in the recording/mixing chain? How can you recover what has been already "lost"? And what is a preamp anyway, but just another amplification stage? Why should it take out information that all that other stuff doesn't? Logically, it doesn't add up.

However, if we postulate that the music needs something to make up for the inherent artificiality of the entire reproduction chain, it's perfectly conceivable that a single component in the chain will do that. More than one might be better. Seems the problem may be a hang up about purity. DHT's are seen by the DHT only crowd as somehow more "pure". The implication that they might actually add some "impurities", however beneficial, just doesn't jive with the orthodoxy. That's no more useful than the orthodoxy that the only good amp is one with wire with gain (which is true for a laboratory amp). If the point is to create an illusion that works for you (and that's the best you will ever be able to do), then relax and accept sin into your life. If it sounds good, do it.

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Old 12th February 2009, 01:57 AM   #26
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You do need to carefully level match, but that takes nothing more exotic than a good voltmeter.
Historically amplifiers have been measured using static measurements. THD, IMD..... they are all measured under static, unchanging conditions. And yes they are fairly easy to do. A good sound card and some (often free) software and you can make these measurements. We can often measure and talk about slight harmonic distortion differences between diferent amplifiers. Are they responsible for what we are hearing? Do we like the sound of a big solid state wall thumper with 1.21 giggawatts of power and .0000000% distortion? Do all of the amplifiers that measure great sound the same? There must be something else going on here.

However as we all know, music is far from static. Can we make dynamic measurements? That is a hard question to answer. There have been numerous attempts, but the results have been inconclusive. When my daughter lived at home, she and her friends played instruments. My daughter played the drums. I made some recordings using a mike and a PC using cakewalk software. Play the recording through a stereo, and record it again with the same microphone. Then compare the WAV files. I can tell you that the sound of a drum stick hitting the rim of a snare gets distorted. The worst offender is not the amp, it is the speaker. Different speakers do different things to this highly dynamic sound.

Unfortunately I did all this about 10 years ago, and lost interest about 9 years ago. The PC with all the wave files is long since dead. My daughter and her drum set (and xylophone) have been gone for 5 years.

So, we do what Kodak did, build some audio Kodachrome! After all what we want is to please our own ears. What good is an amp that measures real good and sounds like an iPOD?

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The analogy is apt. I love Kodachrome, too.
Kodachrome printed on Cibachrome that was the ticket. Unfortunately when I got married I could no longer justify having a 3 bedroom house, 1 bedroom, 1 electronics lab, and 1 darkroom, so the darkroom went away, and I went over to the dark side (digital). At least all of the glowing tube pictures that I post are photographed through Zeiss glass!
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Old 12th February 2009, 02:46 AM   #27
JoshK is offline JoshK  Canada
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Quote:
Originally posted by SY
Have you tried comparing output to input?

There's a well-known designer for whom I have the greatest respect who believes (not unreasonably) that much of the attractive "vivid" quality of DHT comes from the mechanical resonance of the cathode. That's OK, but it is an addition and signal processing, so should be recognized as such. Which means that there is certainly a reason to use another technology- if you want the electronics to not add "niceness" to the sound but merely to amplify.
That is an interesting observation. It seem reasonable, on the surface, as uncorrelated (if it is that) noise can have a distracting effect on our brain and cause us to focus less on the unnaturalness of the reproduction. I don't know if I am doing a good job of explaining that, but I am thinking of a parrallel with jitter of the uncorrelated versus correlated nature.
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Old 12th February 2009, 05:14 AM   #28
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"Is it worth using anything other than DHTs for preamps?"

Depends: open loop, or NFB?

These small signal DHTs almost always seem to have low u-factors, but with large r(p)'s and small g(m)'s. Does that make a difference?

In the final analysis, if you've got something that you like to listen to, then you done right.
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Old 12th February 2009, 05:51 AM   #29
Bitrex is offline Bitrex  United States
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Why not take two preamps of the same design, one with a DHT and one with an IDHT, feed them with two out of phase signals, sum the outputs in a passive mixer and see what the difference signal looks like?
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Old 12th February 2009, 07:55 AM   #30
Jaap is offline Jaap  Netherlands
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Quote:
Originally posted by Bitrex
Why not take two preamps of the same design, one with a DHT and one with an IDHT, feed them with two out of phase signals, sum the outputs in a passive mixer and see what the difference signal looks like?
Then you suppose that:

- of any sound that is different valued by the brain ear combination of a certain individual than another sound, it is possible to make that change in appraisal (indirect) visible on an electronic measuringinstrument that is connected to the sound producing "system".

- because the sound is produced in a long chain of different components that interact with each other it must be possible that, if you exchange one or more components, you isolate all kind of causes and effects that occur and also prove that there is a relation with the psychological appraisal of it.
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