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

I was interested in the responses to a related post by leemaze this week, saying that a Synchro Mesh was a good way to improve a DAC with subpar jitter.  I have a Cambridge CXU, with an inboard DAC; how could I determine how much jitter it has? 
128x128cheeg
gdhal's avatar
gdhal
1,641 posts
 
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.

But which sounds better? :)
melm
1,084 posts
 
I suppose my response was an "all things being equal" one.  Of course if the rest of the circuit is screwed up, the best jitter clock in the world will be of little use.  So I assumed the circuit was otherwise competently designed and executed.  

A good example of the importance of the clock in an otherwise pretty well designed circuit is the optional upgrade to the femto clock by Wred4Sound.  Apparently the improvement is SQ is undeniable just by going to a better clock.

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?

I'm not here to show off what I know about bad circuits.
audioengr
3,282 posts
 

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

melm
1,084 posts
 
The issue posed by the OP was about a better clock.  So my response was about clocks.

At the current state of the art, a femtoclock, while not a sufficient condition is IMO a necessary condition to the best possible SQ.

Also, generally speaking, if a maker implements a femtoclock, chances are the rest of the unit compliments it.  In other words, it's a good sign of quality . . . generally.  If Steve N. wants to provide exceptions that he knows of, I'm all ears.
cheeg's avatar
cheeg OP
247 posts
 
Thanks, everyone, for your inputs.  Unfortunately, much of what was said went over my head.  Could someone recommend a good, readable reference on dacs?

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