Hi,
An update on USB clocks.
As mentioned above the battery powered TXCO have really been useful in proving to me the value of improved clocks for the transmitting and receiving end of the USB audio link. Messing about with the clocks and with Paul's Paul Pang USB Card showed that there is headroom for sound quality as qlock quality is improved. With this in mind what things have changed again and I hope will be the final stopping off point is now in place.
I ordered a couple of reference quality 3rd party upgrade clocks (Dexa Neutron Stars, that brings the total to 3 of them now in my system !) in special order 24mhz frequency. These are now fitted to the PC PCIe USB card and the NOS1 interface together with matching separate high quality mains powered Dexa linear supplies for the clocks.
What were the results ? Well things are running in so I’ll come back with an update if needed. For now this is what was done and the sound quality changes.
The clocks were put into the music system one at a time to get a feel for their impact.
USB PCIe reference clock.
Putting the reference clock on the PCIe USB board improved sound quality a lot (again ). The Dexa delivers the smoothness and tone of the Paul Pang card with the bass extension and drive of my DIY clock. In addition it extends, cleans, and tidies up music top to bottom. The surprise was the dynamics which are much closer to real presentation very enjoyable to listen to. I would say that the required volume XX setting for a listening given sound pressure level has lowered buy 1.5 to 3 db (eg -33db now sounds like -30db did before) this seems to be down to a much richer and fuller sound but still with detail and not at all congested.
NOS1 USB interface (USB 24mhz) clock added to the above
With the reference clock applied to the NOS USB interface as well as the PCIe USB card things get interesting. Tone especially is much improved, very convincing and easy to listen to for hours. Again hash (that you would not really have pointed out before at all) drops away. Ability to sort out difficult congested tracks is great (there is nothing right now that I can really say trips the system up badly), is like a major cartridge upgrade on a vinyl set up. The system “tracks” the complex and makes much better sense of it.
Now the interesting part with all of this perceived improvement there is a slight reduction on dynamic presentation. Its very slight and I take this to be a good thing. Jitter can falsely increase the perception of dynamics and it sounds to me like what is playing now is much more realistic so Ill keep an eye on this.
With the two changes above in place XX software settings are not nearly so sensitive as before but at the same time different settings are needed. Next step is to tune the software parameters suit the new response of the "down stream" system.
Ill update more as things settle in. For now having made a considerable investment in these clocks on a hunch I can say that I am delighted by the results and there is absolutely no way having heard this that they would come out of the system again.
Now onto packaging of the new components, my poor NOS and PC are looking a like electronics projects at the moment
I know that Paul has also invested in one of these clocks so it will be great to get Pauls impressions as well when he has fitted it.
Cheers Nick.