DACs and bass response?


I'm auditioning dacs in my system. One (COS) was way to analytical, overall, but had very tight bass. Another (Aqua La Voce) is what some would describe as "musical"  and sounds  terrific in all aspects except bass. My cdp alone does better in that regard. I have monitors and no subs. Can I expect that dacs that are hyper-detailed will also offer tighter bass as a rule?
stuartk
Steve,

What is your opinion on the stereophile J-test?

It measures analog out of a DAC to a test signal - so it checks for both incoming and intrinsc jitter.

What do you think of the typical SOTA DACs that have a noise floor at -150dB when tested for jitter?

How can perfect performance be improved upon and what do you look for when testing an asynchronous DAC of this level and how could Synchro-mesh or another cable improve upon perfect?

GeorgeHIFI wrote:

As I mentioned in my first post, it has output coupling caps, that's why many owners on the net are changing that cap.
 
If that cap is too small in uF (microfarads) it will roll off the bass too early giving a shallow subdued (cool) bass, increase this cap 3 x in uF and it should fix the problem and give you a deeper stronger bass.

If its 1uFd or more, this should be sufficient for most preamp and amp loads to deliver bass.  No bass roll-off will occur. 

The real issue is the quality and combination of these caps.  For all caps I have tried with my own DAC, one must add a smaller cap in parallel to get the full range out of it.  Highs are ultimately compromised by using larger caps only.  The best names, Duelund, Mundorf and V-Cap all need this.

Steve N.

Empirical Audio


What is your opinion on the stereophile J-test?

It measures analog out of a DAC to a test signal - so it checks for both incoming and intrinsc jitter.

Much better to measure the jitter directly, although this is all you can do if the Master Clock interface is inside the DAC.  Mildly interesting and only gives you part of the picture IMO because the stimulus is not a true music waveform.


What do you think of the typical SOTA DACs that have a noise floor at -150dB when tested for jitter?

Those are good numbers, but what stimulus is used?  A single frequency?  Not good enough.


How can perfect performance be improved upon and what do you look for when testing an asynchronous DAC of this level and how could Synchro-mesh or another cable improve upon perfect?

I have yet to see or hear "perfect performance".  Every time I make an improvement to my own DAC or converter, I think that it cannot possibly get better, but then it does.  If I had to choose the best DAC for a demonstration, cost no object, I would choose mine, even though it's not the most expensive or even DSD capable.

Performance can always be improved.  If you can drive this DAC with S/PDIF signal and hear a difference with different cables, then it is not jitter immune. A simple test. The Synchro-Mesh and a reference BNC cable would likely improve the SQ from it.

If it is an internal Ethernet or USB interface, making changes to the power delivery to the clock circuits and buffers will likely improve it. Sometimes even making changes to the ground-plane or voltage regulators will improve it.  Performance in high-end audio is mostly about good power delivery, which includes optimum board design, power supply, regulators and decoupling caps.

I modded DACs and other digital gear for 10 years and I was able to improve any product a customer would send me.  This is precisely what gave me the bag of tricks that I use on my own products. Given enough time tinkering, I can probably improve them even more too.

Steve N.

Empirical Audio



If its 1uFd or more, this should be sufficient for most preamp and amp loads to deliver bass. No bass roll-off will occur.
Your assuming it's 1uf if it is (and it's plastic looking at the net pics) and it's look at maybe a class-D which many are 5kohm input the the bass roll off is going to be -3db at 32hz. If the cap is only .47uf the the bass roll off is going to be around -3db at 64hz.

As I said before there are many owners putting in big plastic caps in place of what there from the factory which seem to be small in physical size, but still plastic.  

Cheers George  
As I understand it the J-test was developed by Julian Dunn in the mid 90’s.

It appears to be the best test found so far and is used by AP in their lab test gear. (I dont agree with probes on legs of DAC chips as the probe itself is likely to affect the device itself when measuring timing to such accuracy. I think the J-test known test signal in and a careful look at the perfection of the analog out is much more representative as it tests the DAC as a whole as it is designed to function and including the clock timing accuracy)

A LSB square wave at Fs/192 which produces harmonics right across the audio range. This square wave is coupled with a high level sine wave at Fs/4. The sine wave being a very intense digital full on/off work out (nasty stuff that should produce logic Induced modulation in anything but stellar equipment)

Looks like an extreme DAC jitter work out or jitter stress test to me!

No doubt jitter is still there even on the best devices but to have analog artifacts of jitter sitting below a -150dBfs noise floor seems exceptionally good to me.

https://www.stereophile.com/content/case-jitters