Slow playback after replacing crystal on soundcard

[terranigma]

I tweaked with my cmi8788 based soundcard by replacing traditional crystal oscillator with Rakon brand oscillator chip at same 24.576mhz.

I thought that if i could supply oscillator chip via clean power source then it would be an improvement.

I removed two little capacitors and crystal and applied oscillator chip like schematic below.

It worked but playback is too slow. Rebecca Pidgeon sings like Hulk Hogan.

I tried 10 nf cap, 100r resistor at output and 3.3v supply but same result.

I used oscillator chip from an old soundcard. Maybe it's a faulty or non accurate chip.. have you any idea?

[kevinkr]

Have you measured the oscillator to make sure it is actually producing a 24.576MHz output? You might also try a new oscillator module from one of several sources like Tent Labs, etc.

[Eric_R]

Why don't you remove the 1M resistor also, it leaks signal from XO to XI.

[wa2ise]

Originally posted by Eric_R
Why don't you remove the 1M resistor also, it leaks signal from XO to XI.

I agree, that resistor may be what's goofing it up.

[weissi]

I would also put an series resistor of ~100Ohm between Oscillator Output and CMI8788 Input. Otherwise you might get some ugly overshoot.
But I'have modded my CMI8788 in a similar way, so it should work.

[terranigma]

Originally posted by kevinkr
Have you measured the oscillator to make sure it is actually producing a 24.576MHz output? You might also try a new oscillator module from one of several sources like Tent Labs, etc.

I have no any facilities for measuring. I'm trying to find another one at the moment. If i could find Crystek or Petermann Technik brand low jitter oscillators, it would be good enough instead of expensive ones.

Originally posted by Eric_R
Why don't you remove the 1M resistor also, it leaks signal from XO to XI.

First, i tried without it, when this problem occurs, then i resolder it after checking for similar modifications. Then, i will try without it again...

Originally posted by weissi
I would also put an series resistor of ~100Ohm between Oscillator Output and CMI8788 Input. Otherwise you might get some ugly overshoot.
But I'have modded my CMI8788 in a similar way, so it should work.

My soundcard is Club3D Theatron DTS (Bluegears B-enspirer). I tried with 100ohm resistor as i mentioned in first message. Which parts did you remove? Did you remove 1M resistor? Can you give a little explanation please?

[weissi]

I also have the Theatron. Basically I have removed the 1Meg Resistor plus the to ceramic caps and connected the output of the oscillator via a 100Ohm resistor to XI of CMI8788. But I used an 3.3V oscillator. Normally this shouldn't effect the CMI8788 but I don't know if its Ports are 5V tolerant....

[terranigma]

Originally posted by weissi
But I used an 3.3V oscillator. Normally this shouldn't effect the CMI8788 but I don't know if its Ports are 5V tolerant....

Maybe this is the trick. That seems it wouldn't be clear unless getting a new 3.3 oscillator.

Thank you all.

[weissi]

I have used this one, although not low jitter, but I guess it will work much better than the crystal oscillator that's onboard:

http://at.rs-online.com/web/search/s...duct&R=4785216

[terranigma]

I ordered Crystek C3391 's from Mouser. I have to find a low noise regulator solution. ON Semi NCP700 looks up for this job with 15uV rms noise level.