Clock input to transport

[joeling39]

Dear all,

I must admit I am a novice in DIY Hifi. Recently, I experiemented with PC sound card & was quite impressed with what I heard. However, I still feel that there is room to improve. basically, I am using a PC with sound card digital output & HDD to replae my CD tranpsort.

My sound card, a RME DIGI96/8 PAD has an add-on module called the word clock module (WCM). The function of the WCM, among other things, is to sync external devices (i.e. a DAC in my application) so that jitter is thorwn out the window (somthing like that). My DAC, the AN DAC 1.1 kit does not have a separate clock signal input or output to allow for this feature of the sound card to be utilised. I am thinking rectifying this situation but am not entirely sure how to go about it. Here is my proposal :

1) Take the M Clock output of the CS8412 receiver ship in the DAC (pin 19) & use it to form a clock out signal & feed to the WCM of the sound card

or

2) Use a precision clock module (e.g. LC clock, trichord clock, Elso clock) to be placed in the PC & use it to feed the input of the WCM.

Do you think I am nuts ? Or the above proposal is something that can work. I am inspired by the following diagram taken form LC audio site.

Regards,
Joe Ling

[jwb]

Word sync inputs don't attenuate jitter, they simpley synchronize two frequency domains. If you want a low jitter system, you need to start with a good master clock and feed that into your DAC. Then feed a divided word clock dervied from the master clock into the word sync input of the sound card. This way you won't need a SRC in the DAC.

BTW, I'm also looking at the RME cards because I need multichannel ADAT I/O for my crossover work. How do you like the card?

[joeling39]

Dear jwb,

Thanks for your insight & correction. I guess a better (revised) approach would be to use a good clock & feed it to the word clock input of the WCM & at the same time feed this clock to the DAC. My problem here is that the DAC 1.1 does not use the MCLK. Instead, it uses the SCLK which is the freq. of the MCLK divided bt 4 (I think). I have looked around & could not find a circuit to divide the clock signal into 1/4 so that I can feed this to the CLK of the DAC while feeding the original clock signal to the WCM. Anyone who can assist in this area would be greatly appreciated !

The RME is a good sound card. I have compared this to my M Audio Revolution on SPIF out & RME is a clear winner. M Audio, which I thought was pretty decent, was clearly outclassed. of course the RME is nearly 4X more expensive. No experience on the ADAT though.

Regards,
Joe Ling

[joeling39]

Ok, after much huffing & puffing, searching & seeking & copying, I come up with a clock divider circuit to divide a clock signal by 4 so that :

1) I can use an after market clock of 11.xxx mhz to feed the WCM of the sound card

2) Use the divided clock of 2.8xx mhz to feed the DAC chip of my AN 1.1

What do you think ? Will this work ?



Regards,
Joe Ling

[rfbrw]

Originally posted by joeling39
Ok, after much huffing & puffing, searching & seeking & copying, I come up with a clock divider circuit to divide a clock signal by 4 so that :

1) I can use an after market clock of 11.xxx mhz to feed the WCM of the sound card

Wordclock runs at the sample rate and in the case of the WCM is 44.1/48KHz or 88.2/96KHz. RME do not seem all that keen on Superclock which does run at 256Fs.

2) Use the divided clock of 2.8xx mhz to feed the DAC chip of my AN 1.1

The four CS4812 signals SDATA,SCLK,LRCLK(FSYNC) and MCLK are all synchronous in the case of the AN1.x. Even though MCLK is not used in this case SCLK,LRCLK and SDATA are all in sync with it which means they are in sync with each other. An external SCLK signal would violate this.

What do you think ? Will this work ?

Back to the drawing board. Not a good idea and it will not work well it the unlikely event it works at all.

ray

[joeling39]

Dear rfbrw,

Thanks for your insight. I have realised my wrong assumption. Word Clock is not what I think it is. Anyway, back to the drawing board as you say.

Regards,
Joe Ling