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Old 26th January 2013, 10:43 AM   #151
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Quote:
Originally Posted by Julf View Post
Just because there are measurable differences doesn't in any way imply that the differences are audible.
Do you mean that you can't hear any differences between solid state devices at all? If you can hear them, it means that they add different kind of coloration to the signal. Do you think that DSP can remove or even alterate that coloration?

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Originally Posted by Julf View Post
Why not? Familiar with control theory?
Because, if all coloration could be removed, we would have a 100% perfect amplifier that does not change the input signal at all. And after that culd be done, we could not hear any differences between the amplifiers.

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Originally Posted by Julf View Post
And where does it say it is a positive term?
In my own listening experience with dozens of solid state and tube devices, that's what I'm trying to say all the time!! I don't care about theories and technologies, sound is all that matters. It seems that you like to measure your devices, and I like to listen them. I'm just OK with your approach, but why you can't be with mine?

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Originally Posted by Julf View Post
I think significant amounts of distortion is bad, whatever harmonic you are looking at.
I have read one university thesis were this was in fact approved to be wrong. Unfortunately it is in Finnish so it wont help you guys. I tried to search for a brief explanation in English from internet, this is what I found from Stereophile:
"It's the overtones, or even-order harmonics, that give a musical instrument—or a voice—its tonal color. So if a tube amp (or preamp) adds a bit more even-order distortion, it matters very little. It won't scrape against the ear. Solid-state amps, on the other hand, tend to produce odd-order harmonic distortion, which, even in scarcely quantifiable quantities, will scrape against the ear—even more than the jagged bits and pieces of digital sound."


McIntosh Laboratories MC275 power amplifier | Stereophile.com.


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Originally Posted by Julf View Post
And since when has "warmth" meant "accuracy" in English (my third language)?
Well, maybe since the same day that "coldness" means accuracy ;=) Once again, a matter of taste.

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Originally Posted by Julf View Post
In many cases you can. There are a lot of audible distortions that are easily measurable.

Shouting doesn't change the fact that a lot of the measurements (requency response, distortion etc.) do correspond to perceived sound quality.
Yes, you can see from a measurement if something is wrong with this one measured variable. But you can't see anything if all other variables affecting the sound are OK or not.

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Originally Posted by Julf View Post
Yes.

Amplifier modeling - Wikipedia, the free encyclopedia

Virtual Valve Amplifier - Wikipedia, the free encyclopedia

"No audible coloration" is very different from "no coloration at all".
So do you mean that you change your Creek to sound like nCore with your DSP? Why won't you?

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Originally Posted by Julf View Post
Would be quite an effort to list all the equipment I have worked with over the years - but it does include things like the Voimaradio tube amps designed by renowned Finnish guru Tapio M Köykkä...
Respect! :=)
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Old 26th January 2013, 11:09 AM   #152
Julf is offline Julf  Europe
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Originally Posted by AlliumPorrum View Post
Do you mean that you can't hear any differences between solid state devices at all?
I wouldn't say "at all", but no, I can not reliably tell any differences between reasonably modern solid state hi-fi amplifiers in a double-blind ABX test. I thought I could tell differences until I actually tried it in properly controlled circumstances.

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It seems that you like to measure your devices, and I like to listen them. I'm just OK with your approach, but why you can't be with mine?
Probably because I am an engineer - I like to understand *why* things sound (or don't, as the case might be) in a specific way, and how to improve it.

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I have read one university thesis were this was in fact approved to be wrong. Unfortunately it is in Finnish so it wont help you guys.
I have no problem reading Finnish

Quote:
I tried to search for a brief explanation in English from internet, this is what I found from Stereophile:
"It's the overtones, or even-order harmonics, that give a musical instrument—or a voice—its tonal color. So if a tube amp (or preamp) adds a bit more even-order distortion, it matters very little. It won't scrape against the ear. Solid-state amps, on the other hand, tend to produce odd-order harmonic distortion, which, even in scarcely quantifiable quantities, will scrape against the ear—even more than the jagged bits and pieces of digital sound.
While Stereophile isn't the most scientifically accurate source, I totally agree with the first part - it is usually the added even-order harmonics that give tube amps the "warm" and "pleasant" sound - but adding harmonics is not accurate. On the second point - modern semiconductor amps have so little distortion (unless driven to clipping) that it is inaudible.

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So do you mean that you change your Creek to sound like nCore with your DSP? Why won't you?
Why would I? Both sound much more neutral than my speakers will ever be capable of. The nc400 just has much better current drive capability and efficiency. No way I would do a 4-way active 1.2 kW system with linear amps.
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Old 26th January 2013, 12:29 PM   #153
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Quote:
Originally Posted by Julf View Post
While Stereophile isn't the most scientifically accurate source, I totally agree with the first part - it is usually the added even-order harmonics that give tube amps the "warm" and "pleasant" sound - but adding harmonics is not accurate.
I hold that tube amps are the more accurate in the mid-range so I don't believe in 'tube warmth' rather 'SS cold' I agree adding harmonics is inaccurate but this is something of a red herring (see below for why).

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On the second point - modern semiconductor amps have so little distortion (unless driven to clipping) that it is inaudible.
It depends how you measure distortion. Presumably you're talking THD in which case I agree. But THD isn't the dominant distortion when listening to music - IMD is. So the fact (undisputed by me) that the THD of most modern SS amps is inaudible is irrelevant in practice. Do you have any multitone IMD measurements for the tube amps you've played with?
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Old 26th January 2013, 01:07 PM   #154
Julf is offline Julf  Europe
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Originally Posted by abraxalito View Post
It depends how you measure distortion. Presumably you're talking THD in which case I agree. But THD isn't the dominant distortion when listening to music - IMD is. So the fact (undisputed by me) that the THD of most modern SS amps is inaudible is irrelevant in practice.
Not entirely irrelevant. For IMD to occur, you have to have a nonlinear system. Nonlinearity also produces harmonic distortion, so there is a correlation between the two. In any case, both are easy to measure.

Anyway, this really seems to have turned into Yet Another Tubes vs Solid State Debate - and if that issue hasn't been resolved in the last 40 years, it probably won't be resolved this week either. All I can do is repeat my original advice to the OP - go for a reasonably-priced pure-semiconductor DAC that is easy to upgrade as technology changes, and add a tube buffer stage to get the tube sound. Yes, in that solution there might be 2 or 3 more semiconductors in the path compared to a minimalist "tube DAC", but will you really hear the difference between 100 semiconductors and 103 semiconductors in the total audio path (probably more like 1000 vs 1003)?
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Old 26th January 2013, 02:24 PM   #155
DF96 is offline DF96  England
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Quote:
Originally Posted by stephensank
Feedback does NOT correct colorations in actual practice, a more often feedback corrects most, but then adds distortion of it's own, due to the time delay involved.
I assume you are referring to re-entrant distortion. This is not caused by time delay. It is simply a matter of algebra. No delay needed. In fact, no feedback needed either. You just need to ensure that a non-linear circuit element 'sees' its own output. Wiring a non-linear component in series with a linear component can be sufficient to see this distortion. Interestingly, the only people who worry about re-entrant distortion are generally the people who don't really understand distortion and/or feedback.

Someone quoted from Wikipedia, which says something like 2nd-order distortion comes from a valve interacting with the inductance of the output transformer. Not true. Don't rely on Wikipedia for audio engineering. 2nd-order comes from the valve itself (and 3rd order, and 4th order etc.).

In the current context "properly designed" could mean not sending the raw output of a DAC chip straight into a circuit (opamp?) which cannot cope with the sharp pulse edges. That requires either a very fast opamp, or a diplexer circuit to divert the HF energy to a resistor. "Properly designed" could also mean not grossly violating the output voltage swing spec of the DAC chip, as almost all 'passive I/V' circuits do; the result is a severe testing of the linearity properties of the chip current sources. 'Passive I/V' 'designers' sometimes seem never to have read (or understood) the chip datasheet.
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Old 26th January 2013, 08:12 PM   #156
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When I speak of bad effects of feedback, I refer primarily to what Nelson Pass was addressing in his "stasis" amp designs. Distortion of non-repetitive waveforms caused by feeding back signal to the differential input of a circuit that has been delayed by time it takes the original signal to get through the circuit. The simpler & physically shorter the signal path, the shorter this delay will be, but it nevertheless exists. Feedback works really superbly on waveforms we can readily measure, but it can work very badly on actual music. I don't advocate that all feedback is bad, just that it needs to be used far more carefully & sparingly in audio circuits than is generally done.
As for passive i/v and dac chips, as an example, published and my own measurements on the PCM63 verify what I hear, that this chip copes extremely well with a 100ohm passive i/v load. My own measurements & ears also tell me that the PCM1702 & PCM1704 cope quite well with 10 and 20ohms. Likewise, I see & hear absolutely no problems with a 6DJ8 or a 2SK170 jfet coping with the pulse edges from these chips.

Mr. Julf:
"I wouldn't say "at all", but no, I can not reliably tell any differences between reasonably modern solid state hi-fi amplifiers in a double-blind ABX test. I thought I could tell differences until I actually tried it in properly controlled circumstances."

Really? If this is true, I must further doubt your opinions. But let me give you some hope that I am not prejudiced in the opposite direction of that which I have accused you of being. I think it damn near impossible to design, e.g., a preamplifier that has an entirely tube signal path which I could call "accurate" in the best sense of that word, which I like to qualify by saying "accurately musical". As I said previously, tubes are best used for voltage gain & transistors best used for current gain. Any preamp or power amp needs to do both types of gain in a linear fashion to achieve accurate sound. A preamp is primarily for voltage gain, but it's final stage needs substantial current to drive the line & the amp input, and the amp's final stage needs a lot of current gain to drive the speaker. Tubes just don't do this job extremely well compared to ss devices. But tubes are more capable of linear voltage gain, so I am very strongly an advocate of hybrid designs, where one uses tube purely for voltage gain(to the extent possible, which is not always completely) and ss devices purely for current gain(pretty well always possible). It seems to me that every time I hear anyone complain about tube sound, when queried, I find that their negative opinions have been based on tube gear that has used tubes to also do current gain, such as an all tube power amp, or a *dac that uses tube for final output*, like the stock Monarchy. Had I not added a high-current ss current amp after the Monarchy's tube stage, it would not have a prayer of competing with the other dacs it is now exceeding.

Not to say that there is no such thing as a great all-tube preamp or amp, just that I have never heard one that I could call "accurately musical". However, I have heard tube gear that has sounded so utterly gorgeous that I did not give a damn about accuracy. Anyone who has heard a Marantz 8B with UK Genalex KT77 or Holland Amperex EL34 output tubes installed, on a great pair of adequately efficient speakers(in my case Yamaha NS2000 w/upgraded internals) would have to agree. The sound is absolutely not accurate, but it made me feel like I had died & gone to audio heaven.
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Old 26th January 2013, 08:31 PM   #157
DF96 is offline DF96  England
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Quote:
When I speak of bad effects of feedback, I refer primarily to what Nelson Pass was addressing in his "stasis" amp designs. Distortion of non-repetitive waveforms caused by feeding back signal to the differential input of a circuit that has been delayed by time it takes the original signal to get through the circuit. The simpler & physically shorter the signal path, the shorter this delay will be, but it nevertheless exists. Feedback works really superbly on waveforms we can readily measure, but it can work very badly on actual music. I don't advocate that all feedback is bad, just that it needs to be used far more carefully & sparingly in audio circuits than is generally done.
As I said, time delay is irrelevant in audio amplifiers. It becomes an issue for higher HF or VHF amplifiers, at 1000 or 10000 times the frequency of audio. People sometimes confuse low pass filtering with time delay; I assume that is the case here.

I do agree that feedback has to be used more carefully than some do; in some cases this might mean using more feedback, not less.
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Old 27th January 2013, 07:40 AM   #158
Julf is offline Julf  Europe
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Originally Posted by stephensank View Post
Really? If this is true, I must further doubt your opinions.
As you should - doubting is good, and verifying facts is even better.

Have you ever "tested" your golden ears in proper, controlled, double-blind ABX situations?
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Old 27th January 2013, 08:19 AM   #159
marce is offline marce  United Kingdom
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I do believe that there has been numerous occasions mentioned, where in blind tests most people who tried could not distiguish between solid state amps. I have tried at home with my amps and could not distinguish between them. Not one of the chosen ones who can hear a wasp F*** in a thunderstorm, but at least it allows me to enjoys my systems, one valve one solid state.....
On design I find it strange that there is so much argument, you cant design without measurements, certanly you could not design a product by listening alone. And by the same token you have to test what you design and part of the testing (assesment) is listening.
I just wish I could be so sure of my delusions that I could believe what I hear, but I dont trust my brain, so I always have a bit of skeptism regarding what I hear and whether I percieve changes, so cant be so arrogant in my views regarding listening tests. These are hard enough when only yourself is involved (self delusion) when there are numerous people involved...
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Old 27th January 2013, 08:51 AM   #160
Julf is offline Julf  Europe
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Originally Posted by marce View Post
On design I find it strange that there is so much argument, you cant design without measurements, certanly you could not design a product by listening alone. And by the same token you have to test what you design and part of the testing (assesment) is listening.
Absolutely. You design by numbers, and verify the result both by measurements and listening.

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I just wish I could be so sure of my delusions that I could believe what I hear, but I dont trust my brain, so I always have a bit of skeptism regarding what I hear and whether I percieve changes, so cant be so arrogant in my views regarding listening tests. These are hard enough when only yourself is involved (self delusion) when there are numerous people involved...
Indeed. I used to believe I could hear all sort of system differences - until I actually verified it, and realized how powerful an effect perceptual bias can be.
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