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UPGRADING THE CRYSTAL (X0) ON ESSENCE STX - Page 7

post #91 of 238
Thread Starter 
Please tell us! What caps will you upgrade and whit which one? What capacity?
post #92 of 238
Thread Starter 
I have informed me about the caps upgrade.
Stock caps are very good and when you want to change them the results would be little or maybe worse!
Here are the key MKT caps that stand besides the buffer opamp! This
caps need to be changed because they are not good!
I will change them whit some MKP caps (1,7nF).
Has someone a good idea which firm should I take?
Here is a picture:
post #93 of 238
Hi,

Sorry for the late reply - work is v busy and I'm trying to upgrade the clock on my ST too.

You are right about the white caps - they form part of a feedback circuit and are directly affecting the analogue signal.

I would replace these with Relcap RTE but you might need to solder them in from the other side. I would be very careful about changing the values - you might seriously affect the negative feedback frequency bandwidth. If you look up the datasheet for the DAC, you'll probably find a suggested I/V circuit. Asus engineers seem to go by the book so it'll probably have been copied exactly, values and all. I think it is a PCM1792 ? If so, check page 35 of the datasheet here :

http://focus.ti.com/lit/ds/symlink/pcm1792a.pdf

In a perfect world, you would change the values in this circuit to match your op amps.

There are also some smt caps near the op amps in the I/V stage.



I am looking into replacing them but at this stage I haven't done any measurements to find out what values etc.

The other caps worth changing are the 220uF/270uF electrolytic caps - nine of them in all on the board - they are the power supply caps closest to the components.

Nichicon caps are renowned for being bright and detailed with high-bandwidth - and the card has this sound. Changing the electrolytics can have a surprising effect. It's not that the FG are bad but they have a signature and changing them can help to tune the card to your preferred tastes. I like SilmicII and Philips BC but everyone has their own favourites and finding ones that balance with the rest of the card is the real trick.

Have fun !

Tom

PS Here is a pic of my ST with a Vanguard clock. Still working on this...
post #94 of 238
Thread Starter 
Very nice! How its sounding??
post #95 of 238
Thread Starter 
Here is a picture how to upgrade the clock crystal on stx!
1 POINT: unsolder the stock crystal
2 POINT: solder a wire to point 1(red mark) and connect to output of your new crystal
3 POINT: solder a wire to point 3(red mark) and connect to ground of the new crystal
4 POINT: solder DC 12V power supply wires to new crystal
THATS IT!
post #96 of 238
Hi,

The Vanguard has gnd, 5V supply, and output so I tried to use the ground and 5V supply on the expansion card pins on my ST as they were the closest to the pins on the Vanguard, but for some unknown reason, this didn't work. I am still looking into why but I must admit I am still not sure. I have checked and double-checked the connections and PCB tracks etc. It SHOULD work, but it doesn't. It may be the Vanguard is not suitable but actually, it should be. Um.

I'll keep trying ! I want to get the clock and the power done before anything else because these can have the biggest effect. So when I change caps etc, it will be one of the last things I do - a fine tune almost.

Have you finished your card now ?
post #97 of 238
Strange, if you connected up the GND and the 5V you should be getting a signal on the output. Maybe see if you can get the XO working on a protoboard first as maybe there is something wrong with the XO itself? -If your sure the connections are proper.
post #98 of 238
Yes, strange indeed....

I've been thinking about this for ages now and just can't figure it out.

I'll put the old crystal back on and check the card works fine like that - maybe I did some damage at some point...
post #99 of 238
Where I would start is verifying the XO works as perhaps it was damaged in someway.

If you have power and the conenctions are all correct and you have no signal output, I would say you need a new XO.
post #100 of 238
Thread Starter 
I have spoken to an expert and you should not kidding whit the crystal signal. If the av100 chip does not get the freq. signal it can be damaged...
post #101 of 238
Hi,

I think you're right Rob - it might just be the XO. I'll take it back and get them to test it.

Gworld - damage ? how ? The card still 'works' but all sounds are played back at the wrong speed, so I shut down immediately. If I pumped in a voltage I'm sure that would do damage but no crystal signal just means no PLL lock ?

Cheers
post #102 of 238
Thread Starter 
Ok.
post #103 of 238
I refitted the original XO - card works fine again. I'll take the card and XO into a local shop where I got the XO and see what they say.
post #104 of 238
Quote:
Originally Posted by GWorlDofSPACE View Post
Here is a picture how to upgrade the clock --...
Very nice picture, thank you for sharing
post #105 of 238
PPM has nothing at all to do with jitter. PPM measures how close the oscillator's true (long term) frequency is to the specified frequency. Nothing to do with jitter whatsoever. There are very high ppm oscillators with very low jitter and vice versa.
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