DAC's : The missing feature: Signal quality

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

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

Having some sort of Green/yellow/red indicator about signal quality and noise I think would be helpful. For instance, there are a number of reclockers and signal cleaners on the market. Wouldn't it be nice if our DACs could indicate directly if a particular source might benefit from it?

That would be really nice.  Unfortuntately, the industry does not even have any metrics for jitter versus audible correlation yet.  I'm working on this actually.  Equipment that can actually measure direct jitter accurately is very expensive, on the order of $100K.

Steve N.

Empirical Audio

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 - Purifier??  I don't know what product this is.  Do you mean the Short-Block?

There is no incompatibility with XMOS-based USB interfaces.  Sometimes they need +5V from the USB cable depending on the design.  The SB cuts this voltage.  It doesn't matter because it out of production now.

I would highly recommend this product for USB:

https://sotm-usa.com/collections/sotm-ultra/products/copy-of-tx-usbultra-regenerator-1

This is the ONLY thing I have tried that makes my USB almost as good as my Ethernet interfaces.

Steve N.

Empirical Audio

The OTL upgrade simply removes the output isolation transformer. If the DAC has a transformer on the input, there is no reason to have two in series. The pulse transformer is really not necessary, but helps with ground-loop noise in some systems where the DAC does not have an input transformer. Both the standard and OTL versions of SM reclocker have very low jitter, but the OTL is slightly lower. If you want the lowest jitter, then OTL is recommended. Plugging the AC power for the DAC and the SM into the same outlet usually minimizes ground-loop noise, so the OTL works fine.

Steve N.

Empirical Audio