How can I tell if I need a better clock for my DAC?

The best way to keep jitter to a minimum is to see that your component has one of the high quality, high specification, clocks. If it doesn’t, sell it and buy one that has a great clock.

A good oscillator is a good start, however, there are a lot of other things that take that 80 Fsec and turn it into 200psec. These things include:

1) bad choices for logic family for the associated circuitry

2) poor board design, sliced-up ground-planes and crosstalk

3) Poor power delivery and decoupling caps choices and locations

4) slow reacting power supply and regulators

5) too much sharing of the power between oscillator and other circuits

6) no clever circuit design to minimize jitter

It turns out that these things are actually more important than having an oscillator with 80Fsec of jitter or one with 1psec of jitter.

there seems to be little doubt that the quality of the incoming digital signal (jitter, noise) will affect the amount of correction the DAC has to do and so affects SQ.

Yes, but it’s not correction, it’s simple D/A distortion.

It’s not so much the accuracy of the clock that is important, its the jitter and phase noise specs.

Steve N.

Empirical Audio

This Stereophile AES J-test includes a very high level signal mixed with a LSB (smallest signal) and is a great test for interface jitter and any modulation distortion.

Ex 1. Benchmark DAC3 HGC, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit TosLink data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

https://www.stereophile.com/images/1117BDAC3fig11.jpg

There is no jitter (spurious signal) visible above -150 dbfs noise floor on the analog output. This means there is excellent interface jitter rejection.

—-&————————

Ex 2. Schiit Yggdrasil, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit USB data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

https://www.stereophile.com/images/217Schiitfig12.jpg

There is jitter (lots of low level spurious signal at very specific tones).... probably inaudible but it is there.

Yes, "a good oscillator (clock) is a good start". Without a good start, you have nowhere good to go. So what is this argument about?

The issue is implying that only a good oscillator is required. That's what the argument is about.  It purveys the wrong impression.

This is like saying that only a good D/A chip is required and you have the perfect DAC.  Not by a long shot.

Like most things, the devil is in the details.

Steve N.

Empirical Audio