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Old 20th January 2013, 08:55 PM   #11
kad is offline kad  Canada
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Quote:
Originally Posted by AlliumPorrum View Post
Quote:
Originally Posted by Loren42 View Post
So, what is the point of the project? Are you trying to add some sort of coloration (a.k.a. distortion) to the signal chain?
No, I´m trying to get best possible sound for "reasonable" price. And pretty much all the best DAC's that I have heard have been using tubes.

So basically, the answer to your question is: I'm trying to minize transistor based coloration & distortion from the signal chain, since it seems to be worst kind of coloration for me.
Personally, I think it is the vacuum tube inherent nonlinearities that introduce coloration to the original signal. That coloration or 'musicality' is what some prefer and perhaps mistakenly perceive it as lack of coloration?

Please do not misunderstand the intent of my post. I'm not claiming that transistors are better than tubes. Likewise, I am not convinced of the opposite: that tubes are better than transistors.

The rationales for my reply are:

Since in all likelihood, the signal you now listen to has probably gone through millions of transistors in the recording phase, for digitization purposes, then what is the point of using a tube in the analog portion for the DAC (Digital-to-Analog) reconstruction of these bits, into an analog waveform?

Since music is merely a summation and differentiation (between channels or phases) of fundamental sine-waves (also existing into the pure science mathematical domain) of varying frequency and amplitudes; technically, a fundamental sinusoidal with an infinite summation of harmonics becomes a square waveform.

Experience dictates (to me at least) that it is more difficult to reproduce a square-wave from vacuum tubes than it is from solid-state physics.

The primary reasons IMHO are the 'microphonic' effect that the valve grid (base in bipolar, gate in FET) is manufactured with venerable yet extremely obsolete processes. Just tap on a tube (or a wine glass for that matter), and if any sound is heard at all the physical level, this will reflect into the electrical signal (electrons) propagating from the cathode to the anode.

Furthermore, even low-level tube preamps still require decoupling from the relatively high polarization voltages required by the anode plate. This is accomplished via a magnetic decoupling transformer, which in itself introduces all sorts of non-linearity starting from the fact that hysteresis is a permanent function of magnetism.

In real life terms, the audio quality will be limited not only by the tube, but the inline transformer methodology used to build it and also the materials involved.

Thus I find your thread interesting, and would appreciate to witness a completed project for further personal edification.

I sincerely wish you all the best in your endeavors and beliefs. And good luck with this cool project!


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An open mind will put you in contact with a bunch of eccentrics. At first, their thinking will confound you. Gradually, though, you'll see a method to their madness. Thinking outside the box can yield impressive results.
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Last edited by kad; 20th January 2013 at 09:02 PM. Reason: Inclusion of context as I replied, a multitude of intervening posts occurred
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Old 20th January 2013, 08:57 PM   #12
cotdt is offline cotdt  United States
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Originally Posted by jrenkin View Post
"Doable" or "theoretically possible"?
It's doable... depending on the design, a lot of passive components can be used to minimize the number of tubes needed. There are discrete DACs on the market that sell well relative to their very expensive prices. They have a different sound.
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Old 20th January 2013, 09:03 PM   #13
Julf is online now Julf  Europe
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Originally Posted by cotdt View Post
It's doable... depending on the design, a lot of passive components can be used to minimize the number of tubes needed. There are discrete DACs on the market that sell well relative to their very expensive prices. They have a different sound.
Well, some of the first computers were made with tubes, so if you can make a computer, you can make a DAC, but it will take thousands of tubes, and mean time between failures will probably be weeks or days... Not to mention the amount of power it will consume and the heat it will generate...
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Old 20th January 2013, 09:06 PM   #14
cotdt is offline cotdt  United States
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Many recordings do actually use tubes in the signal chain. For example, mic preamps often use tubes, guitar amps use tubes.

SS amps have lower distortion because of their circuit. Tubes in the same circuit would actually have lower distortion. People don't use these circuits because they don't sound as good.

The value of equipment depends on end user acceptance and how much the market is willing is pay for it. It does not depend on distortion measurements. People are more interested in the soundstage it can throw, the dynamics, the clarity, the realism effect, the tone, etc.
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Old 20th January 2013, 09:07 PM   #15
cotdt is offline cotdt  United States
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Originally Posted by Julf View Post
Well, some of the first computers were made with tubes, so if you can make a computer, you can make a DAC, but it will take thousands of tubes, and mean time between failures will probably be weeks or days... Not to mention the amount of power it will consume and the heat it will generate...
Looking at the discrete designs for DACs... it looks like it can actually be done with under 100 6SN7s.

It will be expensive... so I agree a poor college student who just wants to listen to Lady Gaga shouldn't shell out $20k to build a discrete tube DAC. A hotel CEO who loves audiophilia, it would be nice to have as a showpiece for guests.

Last edited by cotdt; 20th January 2013 at 09:09 PM.
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Old 20th January 2013, 09:22 PM   #16
DF96 is offline DF96  England
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Where can you buy resistors which are accurate to, and/or stable to, 0.0015%? People don't seem to be building discrete SS DACs either, yet they would be much easier than a valve DAC.
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Old 20th January 2013, 09:34 PM   #17
kad is offline kad  Canada
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BTW I think the OP meant a tube output circuitry, not entirely a DAC made with tubes?

This is what I really like about diyAudio, one thing leads to another. While I have my opinion on vacuum tube technology, I stumbled onto this interesting article:

Quote:
http://www.enjoythemusic.com/magazine/equipment/1212/eastern_electric_minimax_dac_plus.htm

Sound Bone Stock
The EE DAC Plus comes stock from the factory with two NE5532P (dual) and two NE5534P (single) op-amps. The tube socket, accessible from the back, comes equipped with one Shuguang 12AU7 dual-triode tube. When solid state output is chosen, both NE5532 and NE5534 are in the signal chain, and when tube output is chosen, only the NE5532 and the 12AU7 tube are in use. When used in stock solid state configuration, the overall sound was detailed, bold, rich, and energetic, with plenty of bass power. While not as smooth and refined as the Weiss DAC202u, music was extremely involving and fun. You will not find some limp, pale, wimpy, and overly-refined sound with the EE Dac; the listener is more likely to be bobbing his head and moving his feet to the groove and simply getting into it. A strong, forward, and dense center image anchors the soundstage, while instruments at the edges of the stage can easily be heard and seen, a nice 3D performance for a somewhat budget DAC. Detailed and exact descriptions of things like soundstaging, level of resolution, and tonality changed with different op-amps, but the general stock sound quality was already very high and enjoyable.

The tube output stage option can be a blessing for many audiophiles, especially for those who do not employ a good tubed component or two in the system. Interestingly, the sound quality difference between solid state and tube output on the EE Dac was not as large as one might have guessed. With the decent stock Shuguang 12AU7, the tube output had a smidge more bass warmth, a bit more uneven upper frequencies, and some of that tube harmonics, which some may call "tube distortion." My system already sports a highly-modified and tweaked Transcendent Grounded Grid tube preamp as well as tweaked-out 2A3 tube amps, so EE DAC's tube output really was not needed to add additional tube magic. In fact, the solid state stage came across as slightly more pure and transparent in my system, but the preference could easily run the other way for systems with less tubes.

Tube And Cable Rolling
With a bevy of 12AU7/5814 tubes in my boxes, I did roll a bunch of them into the EE Dac. Without going into excruciating detail about various tubes, I will mention a few. The often-recommended Psvane 12AU7 was indeed cleaner and clearer, although the degree of change was not huge by any means. E80CC tubes can be rolled into EE DAC without problems, and the Tungsram E80CC did what it usually does, i.e. dynamic, large, and detailed. Raytheon 5814 brought its usual refinement, balance, and clarity, proving once again its well-deserved reputation. The rare Siemens 5814A early long-plates are one of my favorites, and it did power forward with its supreme resolving capability, speed, and cleanliness. However, since the EE DAC Plus also tends to lean in that similar direction, the combo was perhaps a bit too much of a good thing in this instance in this system.

Going forward, I ended up taking out the tube altogether and using the solid state output for most of the op-amp rolling. Taking the tube out did improve the sound a bit in terms of clarity and ease, probably by reducing the power demand on the power supply. It's also reasonable in order not to continue using up tube life when only solid-state output is used. As usual, USB cables and digital cables made their differences. I settled with the Cardas Clear USB cable, which is probably too underrated in the boutique USB cable world. Now it was time for some serious op-amp rolling!

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Old 20th January 2013, 10:30 PM   #18
DF96 is offline DF96  England
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Who knows? Putting a valve immediately after a DAC chip might work better than a poorly design opamp circuit, as valves are better at handling RF than many opamps. A well-designed opamp circuit ought to be better, as it will present the virtual ground which DAC chips assume as their load - so reducing distortion.
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Old 20th January 2013, 10:40 PM   #19
kad is offline kad  Canada
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Originally Posted by kad View Post
The primary reasons IMHO are the 'microphonic' effect that the valve grid (base in bipolar, gate in FET) is manufactured with venerable yet extremely obsolete processes. Just tap on a tube (or a wine glass for that matter), and if any sound is heard at all the physical level, this will reflect into the electrical signal (electrons) propagating from the cathode to the anode.
Someone else's opinion appears to support my perception of the non-linearity (distortion, deviation, coloration) introduced by the 'microphonic' effect in vacuum tubes:

Quote:
Naim NAP 140 clone power amplifier? - DIY HIFI - HIFICRITIC FORUM - HIFICRITIC FORUM : hi fi audio systems forum

Vibration control within an amp is a matter of sound design - there's no need for fancy feet, rubber bits, ebony bits etc etc, just proper attention to component selection, PCB design, physical construction. It's a routine thing in some of the fields of design I have worked in, where sensitive electronics are mounted on bits of equipment which have colossal vibration levels - for instance compressors running at 60,000 rpm, cutting-heads of oil-well drills, probes in the wake of a warship with twin 28,000bhp motors at full throttle, and have managed to get induced vibration effects to well below the LSB of a 16-bit acquisition system (-96dB).

Similarly when I was designing active speakers I specifically tested for the INAUDIBILITY of vibrational effects on the commercial amps I used as well as my own designs. I am sure if it was possible 30-40 years ago it should be a doddle for current designers. Of course if you insist on using valves then you really are cutting off your nose to spite your face - there are huge problems with pickup, especially as the audio field usually uses B9A-based and similar valves. But you will need to attack this at the amp design stage, not try and cure the problems externally.

But the real question is - do these effects actually exist? Are they actually audible? There's loads of anecdotal evidence, on this site as well as lots others, where people have listened with and without various shelves, brackets, pods etc. and claim to hear differences. But of properly conducted blinded, randomised placebo-controlled trials virtually nothing. And of course if a particular aftermarket accessory cures the faults on one particularly susceptible product, you can assume nothing at all about its effect on another product, which if it has any of these faults at all will probably lie in a completely different area.

And of course the manufacturer is in an awkward position - if he has eliminated any vibrational pickup effects and then points out this fairly routine achievement in his publicity material "Will work perfectly on any shelf, any floor. No need for fancy feet, special mains cable" he alienates the dealers who actually make a handsome profit from these aftermarket products.
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Old 20th January 2013, 11:00 PM   #20
kad is offline kad  Canada
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Originally Posted by DF96 View Post
Who knows? Putting a valve immediately after a DAC chip might work better than a poorly design opamp circuit, as valves are better at handling RF than many opamps. A well-designed opamp circuit ought to be better, as it will present the virtual ground which DAC chips assume as their load - so reducing distortion.
I think a properly designed circuitry of any type be it solid-state (discrete or integrated) or vacuum tube based will perform adequately within its design specifications.

However I question your assumption that "valves are better at handling RF than" solid-state. Nowadays, the state-of-the-art RF transmitter/receivers are all solid-state based.

Examples would be cellular towers operating in the Gigahertz range or Lasers (Light Amplification by Simulated Emission of Radiation) which are usually made out of solid-state materials (such as in laser diodes and phototransistors).

Furthermore the distance connecting all these electronic 'modules' practically running close to the speed of photonic light via electrons are subject to electrical distances measured in micrometers and nanometers. As evidenced by current CPU's using 0.28 nM, 0.22 nM eventually reaching 0.14nM at which point we will need to go to graphene nano-technologies.

Thus a traditional vacuum valve macro-technology doesn't even qualify as micro-electronics; having visibly lengthy 'pins' plus connectors (sockets) to introduce artifacts in the transmission line of the electrons would certainly add to some of the 'coloration' so esteemed by some, loathed by others?

But who knows?

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