[325xi]

I've ran into few opinions that tend to advise strongly against getting DAC based on the aforementioned technology.
Can anyone explain the major disadvantages of Delta-Sigma DACs?

 

[Duncan]

1 bit DACs (Delta/Sigma) are a love them or hate them thing...

...Go with your ears... You might find they sound slightly more metallic when compared to the potential lushness of multi-bit DACs... but then again most of the time, the analogue stage accounts for various nasties that can be found in the digital domain

 

[325xi]

They say "True 24 bit Delta Sigma DAC"...

At the end I'll go with my ears, but at this moment I'm interested to understand "why".

 

[Carl]

No delta-sigma DAC really has 24 bit, 198kHz resolution. To do so would require a sampling rate of about 2.8MHz (as they're 1 bit). They're actually quite a bit lower resolution (works out to the equivalent of about 9 bits), and they use noise shapping (ie, cutting the out of band noise from one frequency and pasting it into another, inaudable frequency) so you "don't hear" the difference.

Never did like the technology myself, although there are a few nice sounding DACs out there that use it.

 

[Ferbose]

Quote:

Originally Posted by 325xi They say "True 24 bit Delta Sigma DAC"... At the end I'll go with my ears, but at this moment I'm interested to understand "why".

What is true 24 bit sigma-delta DAC?
As far as I know, 24 bit DACs are mostly 4-5 bit sigma-delta design.
A true 24 bit DAC would use R2R (?) resistor ladders, but it would not be sigma-delta at all.
One bit DACs are sigma-delta DACs but most DAC chips aren't 1-bit either, but 4-5 bit sigma-delta.
No 24 bit DAC in the world actually has 24 bit resolution, meaning 144 dB S/N ratio. All of them self dither due to thermal noise at 19 or 20th bit. This is not to say that the last four bits buried in thermal noise can't be heard, either. Since thermal noise is now dithered by the last four bits, there may still be information in there. I hope I didn't get any of this wrong...

 

[325xi]

Read yourself, http://www.aprilmusic.com/products/products_da220.htm
scroll down to Features.

 

[Carl]

Quote:

Originally Posted by Ferbose No 24 bit DAC in the world actually has 24 bit resolution, meaning 144 dB S/N ratio. All of them self dither due to thermal noise at 19 or 20th bit. This is not to say that the last four bits buried in thermal noise can't be heard, either. Since thermal noise is now dithered by the last four bits, there may still be information in there. I hope I didn't get any of this wrong...

The PCM1704 has a real world 23 bit accuracy in the digital domain, but the analogue circuitry in them doesn't get anywhere near 144db. Best I've seen is high 120s from them, but, well, I haven't really been looking.

All very well and good to have a 130dB + source, but pretty meaningless if your amp and speakers/headphones top out at 110.

 

[JahJahBinks]

see http://www.stereophile.com/features/374/index1.html

 

[325xi]

Quote:

Originally Posted by JahJahBinks see http://www.stereophile.com/features/374/index1.html

Oh well... I'd better not read this.

Now the question. If this delta-sigma design has so many disadvantages versus one major advantage - price, why on the Earth virtually all the known DACs use it, including very high priced?

And, are there consumer DACs using different designs?

 

[DigiPete]

Quote:

Originally Posted by Carl The PCM1704 has a real world 23 bit accuracy in the digital domain, but the analogue circuitry in them doesn't get anywhere near 144db. Best I've seen is high 120s from them, but, well, I haven't really been looking. All very well and good to have a 130dB + source, but pretty meaningless if your amp and speakers/headphones top out at 110.

I read somewhere that the best mics only go up to about 110dB S/N.
So only computer synthesized sounds could possibly get you above 110dB S/N.

 

[Duncan]

Quote:

Originally Posted by 325xi Oh well... I'd better not read this. Now the question. If this delta-sigma design has so many disadvantages versus one major advantage - price, why on the Earth virtually all the known DACs use it, including very high priced? And, are there consumer DACs using different designs?

One simple factor....






...Cost - Its more expensive to make a decent multi-bit setup.

 

[memepool]

Quote:

Originally Posted by 325xi Oh well... I'd better not read this. Now the question. If this delta-sigma design has so many disadvantages versus one major advantage - price, why on the Earth virtually all the known DACs use it, including very high priced? And, are there consumer DACs using different designs?

I think you just answered the question. price is usually the overiding determinent.

Multibit DACs exist, but most are pretty old like my Marantz DA94. To my ear it equals and in many respects betters high-end Delta Sigma machines like Linn's Ikemi.

 

[ezkcdude]

Just did a quick calculation...Assuming a 2 V output at full scale, the value of the 24th bit is roughly 0.24 uV (microvolts). That's a tiny, tiny number, and would have to believe it's well below the noise floor of most consumer audio reproduction systems.

 

[Carl]

Quote:

Originally Posted by ezkcdude Just did a quick calculation...Assuming a 2 V output at full scale, the value of the 24th bit is roughly 0.24 uV (microvolts). That's a tiny, tiny number, and would have to believe it's well below the noise floor of most consumer audio reproduction systems.

Right, the advantages of extra bits is limited, which is why lower resolution, older DAC chips like the TDA1541 and D20400 still sound amazing even when used for SACD and DVD-A conversion.

It never ceases to amaze me how few companies, even in the high end, use multibit DACs.

 

[akwok]

Heads up, the Storm D01/D03 are multi-bit (PCM1702/4)