2. digital
  3. 140110-20253

DAC's : The missing feature: Signal quality

One thing I wish DAC's would provide is some idea of how much jitter and noise a particular input provides. This is something which I think with a little work could be gleaned from the input circuits.

I want something that tells me "woah, that's a really dirty signal coming in, but i"ll do the best I can with it."

One common source of noise is ground loops. Another may be high jitter from a source like Apple TV. This would also help us evaluate the benefits (if any) of various signal cleaners and reclockers.

Best,
E
erik_squires
audioengr
3,282 posts
 
I just returned a very highly regarded high-end low noise DAC. It has some of the best specs in the industry, lowest distortion, lowest jitter, super quiet dark background. It produced super clean, open, two dimensional "sound". Not "MUSIC".

While the digital designers were seeking absolute perfection, they also managed to completely eliminate the three dimensional and sweet sound of music right out of the equation. Could not wait to get back to my older distorted imperfect DAC. Once I did, real music returned.

Seems perfect digital specs on paper don’t always make for good music and maybe some of the good stuff gets filtered out of the "signal quality" to achieve sound perfection, not musicality


Based on 22 years of modding other companies DACs and designing my own, I have concluded that certain things compromise SQ in digital audio.  Here is my prioritized list:

1) Jitter

2) Digital Filtering

3) Poor power regulation and decoupling in both digital and analog sections

4) Compression from too many stages or poorly designed OP-Amp stages or both

5) Poor ground-plane design

6) Long traces on circuit boards, over 1"

5) Insufficient drive from the output stages

Steve N.

Empirical Audio

audioengr
3,282 posts
 

Depending on your budget Ifi Audio has a Usb -3 purifier$129 a steal,  that removes 40 dB of noise , plus regenerates a totally new signal
parts quality excellent

I have 2 iFi SPDIF iPurifiers in my home theater system to reduce jitter.  Makes big difference for movies.  For 2-channel, my Synchro-Mesh reduces jitter more.

Steve N.

Empirical Audio

ianrodger
164 posts
 
I remember a Darko review of a DAC, Schiitt from memory, where he stated that the pulsing (my word) of an input light meant that the upstream source signal was not as good as it could be, due to jitter (again, my word).So, the technology out there.
audioengr
3,282 posts
 

There is no way this was a jitter detector.  This was a classic S/PDIF receiver error detector.  Even my DAC has this.

Most logic families used in DACs are too slow to make these type of determinations.  We are talking about gates with propagation delays of 1nsec trying to detect a jitter of 10psec.  Not going to happen.

Steve N.

Empirical Audio

erik_squires OP
16,041 posts
 
Hey Steve! I saw your purifier on your web site. One thing that caught my eye was incompatability with XMOS based inputs. Is this because they require a +5 V input?
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