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Scott Nixon USB Tube DAC—low distorted version of signal in background, [TOS #6: was “USB sound card”, i.e. hopelessly useless title]
Aura Evolution
post Jul 4 2012, 17:21
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Hello All,

I've got a bit of a problem with my Scott Nixon USB Tube DAC and hopefully someone has come across something similar before. I think it's probably software related rather than a fault in the DAC itself:

In the background whenever music is playing (be it from mp3, flac, wav or straight from a CD) a low level distorted version of the signal can be heard in the background. If I reduce the volume in the player software (I have tried foobar2000, XBMC and MediaMonkey) the clean component of the signal reduces but the level of the distorted version remains the same.

I've got a Behringer 2020 which I have tried which does not produce the problem. In Windows (XP) device selection the Behringer is listed as "USB Audio CODEC", whereas the Tube DAC is listed as "USB Audio DAC (emulated)", which is the only difference I can find between them. Both are just auto-detected by Windows.

Any help is much appreciated.

Thanks,

Joe
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Arnold B. Kruege...
post Jul 5 2012, 10:58
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Best advice I can give you: Find an appropriate recepticle and dispose of the tubed EFX unit.

This post has been edited by db1989: Jul 5 2012, 17:58
Reason for edit: deleting pointless full quote
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pdq
post Jul 5 2012, 13:17
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QUOTE (Arnold B. Krueger @ Jul 5 2012, 05:58) *
Best advice I can give you: Find an appropriate recepticle and dispose of the tubed EFX unit.

+1
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LithosZA
post Jul 5 2012, 14:08
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Isn't the point of tube amps to add distortion to make the sound 'pleasant'?
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pdq
post Jul 5 2012, 14:31
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Even a tube amp can handle line-level amplification without adding audible distortion. It's just not that difficult. Of course, an inexpensive solid state amp would do the job cheaper, smaller, and with MUCH less power consumption and heat generation.

A tube DAC is especially laughable because the DAC itself is almost certainly solid state, and the USB circuitry is definitely solid state. A tube would only provide the last stage of amplification, a function that the DAC chip itself could probably perform quite well without any help.
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Aura Evolution
post Jul 5 2012, 17:37
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Must be something to do with software. Using Windows 7 and WASAPI output has solved the problem.

I don't have a lot to compare it to but to my ears the Scott Nixon sounds better than the Behringer UCA202 (which only costs £25) and my Marantz CD67se, although there's not a huge difference between the Scott Nixon and the CD player. Partnered with an Aura Evolution mk2 amp and Ruark Prologue One speakers.
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pdq
post Jul 5 2012, 17:53
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Unless you have verified an audible difference by ABX or similar testing, your comparison of the DACs carries no weight here (TOS #8). What you hear in a sighted comparison is far more likely to be due to placebo effect.
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Arnold B. Kruege...
post Jul 6 2012, 12:04
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QUOTE (LithosZA @ Jul 5 2012, 09:08) *
Isn't the point of tube amps to add distortion to make the sound 'pleasant'?


That's the claim that is often made by tube advocates.

It is easy to deconstruct.
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skamp
post Jul 6 2012, 12:19
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QUOTE (Arnold B. Krueger @ Jul 6 2012, 13:04) *
That's the claim that is often made by tube advocates.
It is easy to deconstruct.


What claim are you refuting? That tube amps add distortion, or that it sounds pleasant? I've never heard anyone deny the former, and the latter is a matter of taste. I guess I misunderstand what you mean.


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Arnold B. Kruege...
post Jul 6 2012, 12:29
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QUOTE (pdq @ Jul 5 2012, 09:31) *
Even a tube amp can handle line-level amplification without adding audible distortion. It's just not that difficult.


Back in the days when tubes were all we had, a great deal of effort was put into making tubed equipment that was sonically transparent, and there was quite a bit of sucess.

QUOTE
Of course, an inexpensive solid state amp would do the job cheaper, smaller, and with MUCH less power consumption and heat generation.


Actually building tubed equipment, particularly power amplifiers that were sonically transparent was pretty well understood, but it was expensive. Corners were often cut, and as a result most home audio gear from the days of tubes was a little less than sonically transparent. Once some initial difficulties were surmounted which took several years, SS equipment that was sonically transparent became the rule, and it cost less to build and a lot less to maintain.

QUOTE
A tube DAC is especially laughable because the DAC itself is almost certainly solid state, and the USB circuitry is definitely solid state.


I did a study a while back, and found that the best all-tubed DAC that I could find had very limited performance - if memory serves on the order of 10 bits, and with less-than-audio bandwidth. It was a key component in hybrid computers - a kind of computer that was popular in the 1960s and 1970s that used analog circuits to perform calculations that were still too time-consuming when performed using the limited digital computers of the day.

USB interfaces generally have a dedicated microcomputer encapsulated inside them to manage the USB protocol, and would be room-sized if not building-sized if built with tubes.

Therefore as you say, the so-called "Tube DAC" has just a vacuum tube veneer on a solid state core.

QUOTE
A tube would only provide the last stage of amplification, a function that the DAC chip itself could probably perform quite well without any help.


Exactly. Furthermore, the function performed by the tube(s) is fairly non-demanding so it takes considerable anti-engineering to build something that is sufficiently flawed to sound different.
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Arnold B. Kruege...
post Jul 6 2012, 12:43
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QUOTE (skamp @ Jul 6 2012, 07:19) *
QUOTE (Arnold B. Krueger @ Jul 6 2012, 13:04) *
That's the claim that is often made by tube advocates.
It is easy to deconstruct.


What claim are you refuting? That tube amps add distortion,


It is a fact that everything adds at least a little bit of distortion, so its all about "How much" and "Which knid".

Often the claim that tubed equipment adds audible distortion can be refuted.

QUOTE
or that it sounds pleasant?


Whether you know it or not, you're cherry-picking claims, and in the process avoiding the meat of the discussion. ;-)

The tubed amp advocates claim that tubed equipment sounds different and that the difference is generally more pleasurable. Many suggest that the rest of us are missing the boat by not adding tubed equipment to our systems.

Reality is that a lot of tubed equipment sounds no different, and that which does actually sound different would not be preferred by most listeners aside from sentimentality, hype, and other preconceptions.

QUOTE
I've never heard anyone deny the former, and the latter is a matter of taste. I guess I misunderstand what you mean.


The idea that preferences vary considerably when there are actually sonic differences to hear is at least, debatable.

One very non-techncial piece of support for this idea is the fact that mainstream audio gear has been slowly but surely migrating towards better dynamic range, lower distortion and less noise for the past 80 or more years.

Most of the common audiophile lore about the sound of tubed equipment is most likely the results of hype and the placebo effect.

ABX was invented back in the days when there was still a fair amount of tubed equipment around, and the usual result of unbiased listening tests involving tubes versus SS was that the better the equipment was, the more likely it was that the listeners ended up guessing randomly.
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skamp
post Jul 6 2012, 13:01
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I didn't mean to cherry-pick or avoid anything. I didn't know that tube amps were likely to be transparent. Thanks for the clarification.


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Arnold B. Kruege...
post Jul 6 2012, 13:18
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QUOTE (skamp @ Jul 6 2012, 08:01) *
I didn't mean to cherry-pick or avoid anything. I didn't know that tube amps were likely to be transparent. Thanks for the clarification.


IME modern tubed amps are a lot less likely to be transparent then they were in say 1968 or even 1978. The high end audio industry has turned the product category into a collection of EFX boxes.
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