John Curl's Blowtorch preamplifier part II

[dimitri]

It is possible to build a 24 bit converter, but as far as I know no one does.

Try harder, Simon

http://www.bksv.com/doc/articles/dynx_tech_article.pdf

[scott wurcer]

Originally Posted by dimitri

Try harder, Simon

http://www.bksv.com/doc/articles/dynx_tech_article.pdf

Cool, before we get carried away lets talk no-nonsense 24 bit INL and DNL with no gain ranging or other sleights of hand. That is a straight line from 1V to -1V with no deviation greater than 1/2^24 Volts. Instantaneous no averaging allowed, which means p-p noise in the signal bandwidth. That figures out to about 71 pV/rt-Hz not bad, I want one of those.

[Terry Demol]

Originally Posted by dimitri

Try harder, Simon

http://www.bksv.com/doc/articles/dynx_tech_article.pdf

Originally Posted by scott wurcer

Cool, before we get carried away lets talk no-nonsense 24 bit INL and DNL with no gain ranging or other sleights of hand. That is a straight line from 1V to -1V with no deviation greater than 1/2^24 Volts. Instantaneous no averaging allowed, which means p-p noise in the signal bandwidth. That figures out to about 71 pV/rt-Hz not bad, I want one of those.

These guys have the highest DR ADC that, AFAIK, doesn't use gain ranging.
It achieves (specs) a full 24 bit DR at 48k.

They are an interesting company that has a mix of seemingly cutting edge
digital design with some traditional hi-end subjectively driven design.

An example is the abundant use of open loop circuitry. Even their power
amp is void of global or inter stage FB, so it won't win any numbers
races. Gets great reviews though.

[scott wurcer]

Originally Posted by Terry Demol

These guys have the highest DR ADC that, AFAIK, doesn't use gain ranging.
It achieves (specs) a full 24 bit DR at 48k.

Maybe from a 1 Ohm source impedance.

[Terry Demol]

Originally Posted by scott wurcer

Maybe from a 1 Ohm source impedance.

Not the case, but it's irrelevant anyway.

I presume they would only get those numbers in low gain IP mode, 0dBFS =
9.3V RMS. I don't have to tell you this a bit over 4nV/rt Hz which is
achievable, if only on the test bench to verify the spec.

Regardless, if this is in fact a true spec then I say good luck to them - I'd
like a dollar for every stupid thread I've had to wade through that argued the
merits of 24 bits and the ability of ADC's to even come close.

[scott wurcer]

Originally Posted by Terry Demol

Not the case, but it's irrelevant anyway.

I presume they would only get those numbers in low gain IP mode, 0dBFS =
9.3V RMS. I don't have to tell you this a bit over 4nV/rt Hz which is
achievable, if only on the test bench to verify the spec.

Regardless, if this is in fact a true spec then I say good luck to them - I'd
like a dollar for every stupid thread I've had to wade through that argued the
merits of 24 bits and the ability of ADC's to even come close.

Well I can't follow the way they keep throwing around equivalent measurement BW. That's a peak voltage of 12V or more and the answer is within 700nV at every code, thermals? They shouldn't need the hand waving.

[john curl]

B&K?

[rsdio]

Originally Posted by Jakob2

But wrt to dither theory, i think that Widrow and colleagues today argue that, despite theoretical conflicts, gaussian dither is preferable during A/D conversion compared to triangular dither.

I am not aware of any theoretical conflicts. For that matter, I am not even aware of any conflicts resulting from actual listener tests. If you can point to some conflicts, I'd love to read them.

The most I've seen is the claim that listener testing revealed no detectable advantage beyond triangular, but at the same time those tests certainly did not indicate that Gaussian or other dither of a higher order (>2) was worse than triangular. For those specific tests, my first reaction was to intuit that future tests on better equipment might make it possible to discern finer details that might put higher-order dither at an advantage. In other words, my take away was indications that people can clearly hear problems when there is less than 2nd-order dither, but above 2nd-order dither the results seemed inconclusive.

Do you have links to specific articles from Widrow, et al?

[ThorstenL]

Ed,

Originally Posted by simon7000

Would you like to sign a non-disclosure agreement?

I see Pavel is already volunteering, may I say Me2? I am looking at a working on a line of interesting pro stuff, so this interests me immensely.

Ciao T

[ThorstenL]

Hi,

Originally Posted by Joshua_G

Are there any real 32 Bit or 24 Bit DAC chips?

If by REAL we mean that they measure 24 Bit ENOB or more, no.

The ESS Sabre currently leads the field with around 22 Bit ENOB on the DAC Side. Plus, I kind of take exception to the use of lowish bit parts with dither to get there, though some disagree.

On a hardware level the ESS Sabre has enough hardware resolution to handle 16/44 directly (no noise shaping), which is probably why it reportedly sound so good and is so much better than competitors chips. They have given the Chip enough real resolution to take on old multibit chips, but the penalty is a very large die and a cost that makes you think of buying a pair of K Grade PCM1704 instead, if you are me...

If we mean with real 24 Bit's implemented in a multibit architecture, there is the TI/BB PCM1704, however it's ENOB is more like 18.5 Bits. You can theoretically parallel several and implement "analogue oversampling" into the bargain, with 16 pcs in parallel you should get 20.5Bit ENOB without any mathematical tricks.

Then there is the MSB DAC, but last time I looked you could not buy it (internal use by MSB only) which is what we called a hybrid integrated circuit in the old days and the long announced Arda Tech DAC, which to this day appears to be lacking shipping silicone.

If you are lucky, the PCM63 and AD1862 can still be found despite being long discontinued. Both are "only" 20 Bit but they offer close to 20 Bit Enob and as they can run at 8 or 16 Times Oversampling one could combine them with a PWM Modulator to gain 8 or 16 more levels, which is 3 or 4 extra Bits...

Ciao T