About tube DACs?

[AlliumPorrum]

Hey, now I found one interesting option: Audio Note Kits - L3.1 DAC Kit

Does anyone here have experience on these? Not a cheap option anyway since balanced 3.1 costs way over 2k$, but how about the sound quality...?

[Julf]

Originally Posted by kad

As a side note, the reason I believe 32-bit DAC signal processing sounds better than 24-bit or 16-bit is the 'staircase' effect above the SNR floor.

There is no "staircase effect" as the DAC will have a reconstitution filter (sinc function).

It follows that even a 16-bit Analog to Digital Converter (ADC) used to quantify any analog waveform, such as used in the recording industry to produce mere "CD Quality" will have gross amplitude quantization steps (65,536) of them. These are known as .wav files. A CD .wav file can be compressed without any bit-loss via the lossless FLAC codec. Usually the standard specifies 44.1KHz sampling rate.

Then comes "DVD-Audio" quality, mostly 16-bit quantization @ 48KHz sampling rate. But also allows 24-bit quantization @ 192KHz sampling rate.

Then comes "SACD" quality which is a single bit quantization (the prior bit defines the next level) but is sampled at 64x44.1KHz. Currently this is the ultimate in terms of Audio Quality.

Eh?

FLAC allows 24@192, and that is definitely higher resolution than the 2.8224 MHz x 1 bit (64 x 44.1 kHz, but only 1 bit) DSD encoding used on SACD.

It utilizes 32-bit DSP (Digital Signal Processing).

Only 32 bit? For DSP you do need to use a much higher bit depth to avoid rounding and accumulation errors (precisely the cumulative errors you pointed out with the analog signal). That's why most DSP's are 48, 64 or even more bits - but the output is still only 24 or 16.

All my digital audio media accumulated over the years, now truly sounds better! Sweeter. More definition. Things I never heard before, such as the pluck of a string, or the slightest brush of a snare, now become clearly audible. It is like rediscovering a whole new library of music!

Really!

Enjoy the cool-aid!

[DF96]

Dither has a role to play too, but let us not introduce too many facts into the discussion.

I'm not quite sure what this thread is now about. 'Valve after DAC chip' DACs are quite common, aren't they? When properly designed they may sound as good as a conventional circuit; valves don't have to insert noticeable distortion, although some people seem to prefer it when they do. So what does the OP actually want that is not provided by existing designs?

[AlliumPorrum]

Originally Posted by DF96

I'm not quite sure what this thread is now about. 'Valve after DAC chip' DACs are quite common, aren't they? When properly designed they may sound as good as a conventional circuit; valves don't have to insert noticeable distortion, although some people seem to prefer it when they do. So what does the OP actually want that is not provided by existing designs?

Nothing.

Once again, this thread is NOT about:
- some strange "discreet" DAC designs, or any DAC *designs* at all
- tube vs. solid state comparisons
- technical issues, measurements or SNR´s

What I would like this thread to be is:
- experiences and recommendations on high quality DIY tube kits
- comments on tube DIY kits against high end commercial ones

Thanks!

[cotdt]

You might be interested in taking a look at the Lampizator page. He is both DIY and commerical, and his tube output stage is well regarded.

[DF96]

Lampizator's designs and views are certainly not universally "well regarded". It is a while since I last looked at his website, but "best avoided" would be my verdict.

[kad]

Originally Posted by AlliumPorrum

Nothing.

Once again, this thread is NOT about:
- some strange "discreet" DAC designs, or any DAC *designs* at all
- tube vs. solid state comparisons
- technical issues, measurements or SNR´s

What I would like this thread to be is:
- experiences and recommendations on high quality DIY tube kits
- comments on tube DIY kits against high end commercial ones

Thanks!

Since you are the OP, I shall respect your wishes. Please forgive the next few replies (I feel compelled to correct some disinformation); after which I'll only focus onto your wishes which also happens to correspond to mine.

Cheers!

PS: Beer And Food and Music is good.

~~~~~~~~~~~
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This world is comedy to those that think, a tragedy to those that feel.
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I would propose that life is very much like a game and that a comparison between the two is very enlightening. In any game, you need to be fit, possess certain skills and have a good knowledge of the rules in order to participate. In life, we need to have a good knowledge of the rules that apply and to use this knowledge continuously in order to assess and make decisions in every situation that we face. The more intensely we play the game of life, the better our knowledge and application of the rules, the better the results we will achieve, much like a football player who is skilled, trains hard and knows the rules.

During the course of our lives we progress from being dependent on our parents for food and shelter and emotional support, to being independent as we become young adults. We learn to make decisions for ourselves, and as we see the results of our decisions we get feedback and the resultant experience adds wisdom to subsequent decisions.

The next stage is to develop relationships with others, or interdependence, and it is through these relationships that significant personal growth can occur. Many of us however have a low sense of self-esteem which holds us back in relating to others.

How then do we make significant progress in our lives, as evidenced by personal growth or an increase in wisdom? We look at the results we have and are achieving in our lives. If our results are unsatisfactory, we reassess our beliefs and make adjustments to our actions. Additional important feedback is our emotions (fear, anger, unhappiness, disappointment etc.) which acts as warning signs and which leads us to evaluate either our rules or beliefs, or our actions. Our target is to lead a joy-filled, intense yet balanced life, leading to good life results and continually increasing wisdom.

Author's Bio:
Tony Orbin is a chemical engineer with a passion for the field of self-improvement. He is in the process of starting to give courses in this field. Tony can be contacted on aorbin@iafrica.com.

[stephensank]

Originally Posted by AlliumPorrum

Hey, now I found one interesting option: Audio Note Kits - L3.1 DAC Kit

Does anyone here have experience on these? Not a cheap option anyway since balanced 3.1 costs way over 2k$, but how about the sound quality...?

I have a good deal of experience on a very, very similar, earlier AudioNote dac, with the same AD1865 dac chip & i/v transformers, but a different tube selection. I was not terribly impressed, even after upgrading many of the unit's shortcomings. I think they have taken a step down from that earlier unit on this one, in choosing the oddball 5687 tube for output. There is no good reason to use this tube versus a conventionally-pinned-out 12a*7 or 6DJ8 type, and I have always found it extremely close to impossible to find 5687's that both sound good & are not badly microphonic. All of the good, vintage ones seem universally microphonic. I have also found AN's circuit boards to be of fairly poor quality, with very thin aluminum cladding & poor quality plate-through holes. The transformers they use for i/v, despite what they tout about them, seem to be the limiting factor on sound quality, at least with their AD1865 based units. They don't seem to be nearly as good as they should be, or have ill-chosen primary impedance for the dac chip and/or ill-chosen pri:sec ratio.

My suggestion would be a Monarchy 24 dac, with a fair amount of upgrading/alteration. Very reasonable average used cost, and not too hard to make into a seriously superb sounding dac. Main thing they did wrong is to not factor in that the SRPP circuit used after the passive i/v resistor only sounds it's best at one specific load impedance, with the distortion rising sharply more than one percent above or below that value. So, the key is to either feed it to a preamp with a known input impedance that calculates, with the unit's internal 220k output load resistor, to the right(42k by my running measurements) ideal load impedance for the circuit, or add a very high quality buffer stage, with it's own input Z calculated to total 42k with the 220k unit's load. I prefer the latter approach. Sounds really spectacular. The failure to account for the SRPP's specific load demands is no doubt why the 24 has gotten mixed reviews, from glowing to tepid, as the stock unit will sound very, very different according to each preamp's input Z.

[kad]

Dear All:

Please forgive my multi-posts here, but I'm hitting the limit on the number of quotes within a single post reply. Thus I shall organize them by paragraphs.

Originally Posted by Julf

There is no "staircase effect" as the DAC will have a reconstitution filter (sinc function).

Oh yes there is a staircase distortion. The DAC output low pass filter is designed to have a time constant following the Nyquist-Shannon sampling theorem.

Which basically states if one samples at 44.1KHz (44,100 samples per second) then the highest sinusoidal waveform that can be faithfully quantified and then later reproduced is 22.05KHz.

This only relates to the sampling interval. Then comes in the amplitude of the sampled signal, in the case of a 16-bit ADC/DAC means 2^16 or 65,536 levels of amplitude that can be captured.

What you call the reconstitution filter (analog low pass) must then be able to pass from 0Hz-dc to 22.05KHz ideally without altering the signal in any way, but must reject any distortion component above 22.05HKz by at least 95 dB, which is practically impossible to achieve using analog methods.

You can get a simple low or high pass filter using R/C constant (via a capacitor and resistor) of the first order @ 6dB/octave type. Second order filter @ 12dB/octave. Third order filter @ 18dB/octave. The problem is phase shift. The more filters sequences, the more phase distortion of the signal. What 'tube' audiophiles would call 'pace' or 'coherance' or 'sound stage'... While some others, more eclectics, use the proper terminology 'phase'.

Here is an excerpt on the subject:





Further details can be revealed by actually reading the PDF.

Much more detailed info here:
Fundamentals of Sampled Data Systems - Analog to Digital Conversion
(Of use only if one reads it, alas)

Oh do you remember the first high-power amplifier brand? Phase Linear (of Bob Carver's fame)?

And there are less anti-aliasing glitches with a smoother waveform rather than a gross one. So oversampling the 16-bit quantization at 32-bits depth produces substantial and tangible results. Towards perfection.

Have you even actually auditioned what I am talking about? I suspect not.

Bottom line: your 'reconstitution filter' is what affects the sound quality, or 'coloration' for some? And the exact same principles would occur whether using solid-state or vacuum tube technology (as far as the low pass filter is concerned).

PS: It would be nice towards the diyAudio members community, if you would post some independent verifiable substantiation to support your claims and beliefs. Just say'n.

~~~~~~~~~~
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[kad]

Continued from above.

(Apologies, I forgot to include a link to the PDF, so here it is.)

Originally Posted by Julf

Eh?

FLAC allows 24 @ 192, and that is definitely higher resolution than the 2.8224 MHz x 1 bit (64 x 44.1 kHz, but only 1 bit) DSD encoding used on SACD.

How so? Since the 'master' recording usually is in DSD format? And require conversion from DSD to PCM for most?
SA-CD.net - FAQ


Are you saying that a FLAC encoded @ 24 bits / 192Khz is definitely superior to SACD? Oh really?




Then please tell us where to find a DSD compatible DAC, high-end or low-end, tube or otherwise for under $2K? With a true 32-bit DAC and 32-bit Signal Processing?

While I might propose a potential solution?
Pioneer DSD SC-67




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