Emotiva UMC-1 Audio board clock mod

[tubeing]

Hi everyone,
I'm thinking about replacing the xtal of my UMC-1 analog board with something more stable. Could you suggest me some clock modules? It's the first time I have to deal with clock mods, so any hints will be appreciated! I've found modules from Tents, Effective Audio Mods, Valab, Burson Audio, but other suggestions are welcome. Naturally, if the clock module use a well regulated, low noise power supply it'll be better.
The crystal is used as OSC input (XTI/XTO) for a cs497004 DSP, then I think the clock is routed all over the digital part of the board. The DSP specs say external crystal load capacitance (parallel load) 10-18pf load and 50Ohm max crystal equivalent series resistance. The mounted crystal is a zgc metal can running at 24.576MHz, with an ESR of 120Ohm max, if the datasheet i'm reading is the correct one, 30ppm.
Clock modules found in the web are crystal's direct replacement? I mean, a crystal must be excited from a specific circuit to work properly, while usually clock modules output a square wave and it's not the same...Maybe I'm saying horrible things , but I need to understand things clearly before doing something
Thanks in advance.

Stefano
Stefano

[singa]

Hi, A crystal is just that, which means it consist of crystal resonator
in a metal can when fed a dc voltage it will oscillate at the frequency
depending on how the material is cut,eg. AT or XT etc. also the waveform
is a sine wave.The crystal is only part of an electronic oscillator circuit
which acts as the regulating part (frequency) to the actual invertor circuit in the ic or dsp in your case.The waveform is also square because it is switching
on and off except that it is continuous because of 100% feedback.

Clock modules depending on the design may just be a standard crystal
oscillator in a metal can with the active circuitry included which mean that
supplying a dc power is all it takes to ocillate to produce a square wave because the circuitry is digital.Because moudule is external to the ic it is
less affected by circuit noise,it's selling point.Others may include dedicated
or it's own power supply which is not that great either with standard
7805/lm317 type voltage regulators.

If your crystal has accuracy of 30ppm it is as good as you can get and
I don't see any need to upgrade. The specifications that these clock
providers give is dubious as there is no proof except what they say.Yes
there are 1ppm clocks and they are not cheap and what's the point of it
when your power supply is normal 7805/lm317? You need a good power supply.But those that say super regulator is also doubtful.

If you really want to learn then go to Agilent website (HP) and
download articles about frequency counters and clocks.And you will
laugh when these people try to sell these clock upgrades.How about
a GPS disaplined clock oscillator or atomic clock? Now that's what I call a ultimate clock upgrade. If what you have gets the job done then it is enough.