upgrading CD clock - TCXO

02GF74

Member
2010-07-13 1:38 pm
I am looking at trying out some tweaks on a Marantz cd player and often come across replacing the crystal by a low jitter clock.

So I've been looking a TCXO that have very low jitter e.g. vanguard TCXO as sold on ebay but reading a bit more about it, seems they are no better than a decent xo circuit. So is it worth trying the TCXO? (this is attractive due to the small package vs a small circuit board for an XO circuit)

What are alternatives - I'm sure this subject will have been discussed before.
 
TC means temperature compensated. This reduces long-term drift - irrelevant for audio but very relevant for communications etc. It does not improve short-term jitter (important for audio, up to a point) and may, perhaps, worsen jitter. Having said that, a TCXO may be a good quality oscillator with a good quality crystal and it is that which matters. If you can find an XO with the same quality as a TCXO then you don't need the TC!
 

02GF74

Member
2010-07-13 1:38 pm
Do clock mods ever improve anything, especially when a long cable is used to connect the clock to the board... doubt it unless the original circuit is so bad...

From what I read, the lower the jitter the better. I can't see how a cable can make the jitter worse.

re: oxco, that is a possibility as there are small 14 pin DIL packages available, just need to find one for 16.9344 MHz.
 
02GF74 said:
I can't see how a cable can make the jitter worse.
What if your cable introduces RF interference? Or couples ground-bounce into the circuit? As marce says, unless the original oscillator is particularly bad any 'upgrade' is likely to be worse; even a perfect oscillator badly coupled in will make things worse. How are you going to check that result is an improvement - measuring jitter is not easy, and 'hearing' jitter is prone to all the usual audio 'upgrade' biases.
 

02GF74

Member
2010-07-13 1:38 pm
if you cant see how a cable can affect jitter , you should better live your device like it is !!! ;-) lol

in audio every small change affect the result :)

.

That would depend on the switching voltage on the clock input as well as the voltage level of the interference.
For example CMOS switching levels, which is the likely technology for the chips, I'd be very surprised if voltage of 1V or more will be picked up by the wires, and these wires are not wound round transformers or anytihng crazy like that.
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anyways, let's get back to the original question of improving the clock.

The clock is crystal with two capacitors, I 've read somewhere that it can be improved by using a buffer with its own low noise power supply, such as circuit ont the irgh below.
[IMGDEAD]http://www.kyocera-crystal.jp/eng/wp-content/uploads/2014/09/osc_01e.gif[/IMGDEAD]
 
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