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Old 20th January 2013, 10:06 PM   #21
cotdt is offline cotdt  United States
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kad, I can't seem to understand what point you are trying to make.
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Old 20th January 2013, 10:50 PM   #22
kad is offline kad  Canada
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Quote:
Originally Posted by cotdt View Post
kad, I can't seem to understand what point you are trying to make.
Please forgive my convoluted logic?

What drove me to reply was the OP's statement:
Quote:
Originally Posted by AlliumPorrum View Post
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.
This peaked my interest and triggered my reply. While I don't pretend to know which is 'better' than the other, as I believe there are specific tools best suited to each particular task; my point was that coloration is a property of vacuum tubes technology. Whether that adds or detracts from the enjoyment of music is a completely subjective and personal matter for individuals. Further amplification of the subjective topic here.

Back to topic: Speaking of buffering after the DAC resistor switch array, this damn fast buffer (now probably defunct since NS was bought by Ti?) would probably be a candidate worthy of consideration?
Click the image to open in full size.

Quote:
damn fast op amp datasheet and application note, data sheet, circuit, pdf, cross reference | Datasheet Archive
Abstract: National Semiconductor Semiconductors Linear I.C.'s- Operational Amplifiers LH0033C LH0033C, LH0063C LH0063C Fast and Damn Fast Buffer Amplifiers GENERAL DESCRIPTION The LH0033C LH0033C and LH0063C LH0063C are high speed, FET , amplifiers, op amp isolation buffer for driving reactive loads and high impedance input buffers for high , , see AN-48 AN-48. * FEATURES Damn fast (LH0063 LH0063) 6000V/uS Wide range single or dual supply operation , degrees Fast rise times 2 ns High current gain 120dB High input resistance 101°0 ABSOLUTE MAXIMUM ...
Now 6000 volts per microsecond slew rate, that ought to be able to provide decent square waves?

Just attempting to contribute to this discussion and these diyAudio community forum knowledge base, best as I can.

Cheers to all!

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Old 20th January 2013, 10:58 PM   #23
cotdt is offline cotdt  United States
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That's true... tubes will have their own coloration. The OP needs to be more specific.

How would one know that the reproduction will not have colorations? There are just too many factors involved.
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Old 21st January 2013, 10:34 AM   #24
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Quote:
Originally Posted by kad View Post
BTW I think the OP meant a tube output circuitry, not entirely a DAC made with tubes?
Well I didn't even know that there are so many different kinds of tube DACs...

But, if I have understood correctly, when we talk about "normal" commercial tube DACs, we are talking about tube output circuitry, aren't we?

And just to be sure; actually I really don't care about different technologies or implementation methods or if there are tubes or not. But, as I said, the best commercial DACs that I have heard have always been using tubes (on output?). And that's the only reason why I'm interested on them. I have heard lots of 3-5k€ solid state DACs, and none of them comes even close to DACute, for example. And I prefer the balanced MHDT over any < 2k€ DAC that I have heard.
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Old 21st January 2013, 01:01 PM   #25
marce is offline marce  United Kingdom
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As the signal is digital up to the output of the DAC, the tubes are only going to have any affect on the analogue output. If you managed to build a DAC section from tubes, as long as it didn’t affect the signal integrity of the digital waveform, it would not make any difference to the output. But the question is could you build a DAC out of discrete tubes that would be as good as a silicon based solution, nope, and not with the rise times of todays digital signals, the stray parasitics between the tubes (caused by the long traces required to get the signals from a to b) would probably destroy any signal integrity, plus size and power requirements would be ridiculous. So for the actual conversion a DAC chip is going to be the best solution, with a tube output stage if you wanted. Not only that but building a discrete tube DAC stage is very likely to be noisy in EMC terms, so youd require a hugh great metal case to try and keep the extra EMC noise from polluting everything around you.
DF96 was probably referring to tubes getting less upset over stray RF than some op-amps, ie the op-amps likely to be used for the output stage of a DAC.
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Old 21st January 2013, 02:54 PM   #26
kad is offline kad  Canada
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Apropos, here is another high-end tube output DAC thread I stumbled upon. This may be of use from the perspective there is yet another "Maverick D1 Pre-amp" which unfortunately is a bit obscure to me, since diyAudio doesn't return much more info when searching for this term?

Quote:
Originally Posted by kad View Post
Quote:
Originally Posted by dmbaile2 View Post
I was trying to disable the "direct" switch which bypasses the volume knob. The switch has led to trouble in the past, it will get flipped and blast my speakers with more wattage than they were ever designed for...

Anyway, I cut the cable directly next to the plug thinking that it would disable it... It didn't.. In the pictures it looks like a plug but it actually is not, which is why i had to cut it. There is plenty of room for me to re solder it.

But is there anyway for me to disable it?
Click the image to open in full size.
The "direct" Switch is all the way to the left.
  1. I would suggest carefully reconnecting whatever you cut.
  2. It is possible to disable a bypass switch but you must find the appropriate portion of the switch used. Only then can you disconnect the wire going to that terminal.
  3. It might be helpful if you removed the volume / bypass switch assembly? For inspection of the PCB traces? If the potentiometer and switch go to the PCB, it is possible no wire can be disabled. Thus you must look at the traces on the PCB and find the appropriate cut.
Please focus onto the potentiometer LEVEL (volume control) R47 as an example of the way your volume control works.

The bypass switch simply shorts the portion of the resistor on the wiper arm gliding over the surface. Thus 'direct' I suppose?
Click the image to open in full size.
And then again, I could be wrong? Good luck!

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Old 21st January 2013, 03:10 PM   #27
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Quote:
Originally Posted by marce View Post
As the signal is digital up to the output of the DAC, the tubes are only going to have any affect on the analogue output. If you managed to build a DAC section from tubes, as long as it didn’t affect the signal integrity of the digital waveform, it would not make any difference to the output. But the question is could you build a DAC out of discrete tubes that would be as good as a silicon based solution, nope, and not with the rise times of todays digital signals, the stray parasitics between the tubes (caused by the long traces required to get the signals from a to b) would probably destroy any signal integrity, plus size and power requirements would be ridiculous. So for the actual conversion a DAC chip is going to be the best solution, with a tube output stage if you wanted. Not only that but building a discrete tube DAC stage is very likely to be noisy in EMC terms, so youd require a hugh great metal case to try and keep the extra EMC noise from polluting everything around you.DAC.
Ok, now please let's forget these "discrete tube DACs" or such. As I said in the first post, "What I'm looking for is a tube DAC kit that would sound quality wise be a clear step up from MHDT, but wouldn't cost quite as much as those high end commercial tube dacs such as DACute".

If I have understood correctly, both MHDT and DACute use "normal" solid state DAC ships, and tubes on the analog output section.
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Old 21st January 2013, 03:40 PM   #28
kad is offline kad  Canada
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Quote:
Originally Posted by AlliumPorrum View Post
Well I didn't even know that there are so many different kinds of tube DACs...

1. But, if I have understood correctly, when we talk about "normal" commercial tube DACs, we are talking about tube output circuitry, aren't we?

2. And just to be sure; actually I really don't care about different technologies or implementation methods or if there are tubes or not. But, as I said, the best commercial DACs that I have heard have always been using tubes (on output?). And that's the only reason why I'm interested on them. I have heard lots of 3-5k€ solid state DACs, and none of them comes even close to DACute, for example. And I prefer the balanced MHDT over any < 2k€ DAC that I have heard.
1. You are correct, the output section (analog) could be done with one tube as exemplified in the above picture. So you would achieve your 'tube sound neutrality or warmth' resulting in a satisfying sound you prefer.

2. I do not believe such preamplifiers with tube output would / should cost that much more. At least in part component cost, it's probably only another $20 or $30 more? However, with the marketing appeal of 'tubes' this could go hundreds more? But certainly not thousands? And if they are, then it is a ripoff.

The most expensive part in any preamp (which has to use DACs nowadays anyway) will probably be the Digital to Analog Converter chip itself. Depending on if it is 16-bit, 24-bit or 32-bit deep.

It is simple to visualize mathematically:

2^16 = 65,536
2^24 = 16,777,216
2^32 = 4,294,967,296

From Wikipedia regarding Signal to Noise Ratio
Click the image to open in full size.

So for a 16-bit DAC the Least Significant Bit (LSB) noise floor is: 96.3 dB
Click the image to open in full size.

Similarly, for 24-bit DAC, the level of quantization can resolve: 144.5 dB
Click the image to open in full size.

Finally, for 32-bit DAC, the level of quantization can resolve: 192.7 dB
Click the image to open in full size.

But practically, and in reality, no analog circuitry to my knowledge can have a SNR as low as that, provided by the digital domain. Which means even a 32-bit DAC will be submerged into the analog noise floor. The best I've seen so far in audio implementation sits at around -105 dB noise floor.

So the info might be there digitally, except it is completely obliterated (buried within) by analog circuitry noise floor.

Anyway, I personally believe 32-bit DAC sounds better. But the difference in purchasing price isn't linear. 32-Bit DAC are much more expensive, due to the precision integrated circuit (solid-state) DAC. Not the tube output.

Also DAC require extremely tight precision 'resistor ladder' temperature controlled etc... It is a natural side effect of solid-state microelectronics to have all 'transistors' and intermediate passive components such as resistors matched by the simple fact they are built at the same moment using the same substrate on the chip die. It is an oversimplification, but it makes sense? Whereas in discrete macroelectronics, each resistor, transistor, tube, or whatever must be manually 'matched' with corresponding parts of effective similar value.

Another reason why I think solid-state DAC on a chip are superior to discrete component implementations.

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Old 21st January 2013, 03:58 PM   #29
kad is offline kad  Canada
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Quote:
Originally Posted by AlliumPorrum View Post
Ok, now please let's forget these "discrete tube DACs" or such. As I said in the first post, "What I'm looking for is a tube DAC kit that would sound quality wise be a clear step up from MHDT, but wouldn't cost quite as much as those high end commercial tube dacs such as DACute".

If I have understood correctly, both MHDT and DACute use "normal" solid state DAC ships, and tubes on the analog output section.
Yes you understood correctly.

I still would like to see actual implementations using tube output and a solid-state DAC chip be posted into this thread. I am particularly interested in the schematic diagrams? To see how it's done?

Just out of curiosity?

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Old 21st January 2013, 04:45 PM   #30
kad is offline kad  Canada
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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.

You can visualize the 'staircase' quantization between different types of DAC by the ratios (numbers of steps) above.

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.

The problem with analog circuitry is the noise is cumulative. Which means during the recording & mastering process, each track adds its own noise floor, substantially lowering the available dynamic range.

With digital recording, the noise isn't added, so ultimate recordings do not suffer from distortions, deviations, due to mastering recursive manipulation.

Here is a real-life example of why I believe 32-bit A/D and D/A sounds better. I bought a new receiver this month a Pioneer Elite SC-65.

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

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!

Pioneer Hi-bit 32
Click the image to open in full size.

This YouTube will describe the process and is worth a watch:
Pioneer AV receivers - Hi-bit 32 - YouTube

This YouTube will describe the high-level technical details concerning the SC-65
Pioneer Elite SC-65 - YouTube

The nice thing about that receiver is that it has 9.2 analog outputs. So this is the DAC I'm satisfied with, for my entire sound system.

Hey, I just go for what really works, within my price budget.


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Last edited by kad; 21st January 2013 at 04:57 PM. Reason: Added the specifics to SC-65 via YouTube
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