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-   -   CD master clock (http://www.diyaudio.com/forums/digital-source/22113-cd-master-clock.html)

ftp838 29th October 2003 06:11 AM

CD master clock
 
I am glad to sent my first message in audio.com and English is not my first language, please accept if my expression is not good .
I am using a China make Cd player-Cayin cdt-15A. I have done a few modifications: changed the film caps to old style oil caps, changed the op amp to AD627(ceramic package), changed the tube to Siemen gold pins E88CC etc. Last two nights I just changing the 2 master clocks in the CD.(Where the idea is just come from Audio.com) The player use two Master clocks, one is 16.9344 to drive SAA7327 (Vin is 3.3V), another is 24.576 to drive CS8420 (Vin is 5V) for 96kHz and 24 bit oversampling. I found a TCXO of 24.576 (1 ppm) and another general purpose XO of 16.9344 (50ppm) (just because cannot found TCXO at the moment). Both crystals powered by an 5V old dc-dc converter module made by Ericsson and decoupling by a few caps (1000u,2u,0.1,500p) and it worked fine at the beginning. Both dc voltage of the XO output are less than 5V, so there is no burning problem. Now the player is fine in run-in for about 36 hours and it will continue until 72 hours. The sound is great and the improvement is dramatical. I just want to say modifcation of the master clock is the most worthy to do so for a cd player and just want to share my experience.

Netlist 29th October 2003 08:19 PM

Hi and welcome to the forum.
Elso and Guido among others will confirm your findings; but as I read your post (I know very little about clocks except they wake me up in the morning :D)
you changed almost everything in that player.
How are you so sure that the clock was the most improving?

Well, never mind, it simply must be fun to do and hear all these mods I guess. ;)

/Hugo

ftp838 30th October 2003 01:37 AM

Thanks for your reply!
I changed the things one by one and every change give some solid improvement. The last one is the clock so the improvement is definely identified. Also this time the change is greater than the previous. The most valuable improvement is less loudness but more detials in high frequency, more air in vocal and high frequency hence less fragile to the ear. Smoother bass. Good resolution for some complicated records. ie. hear more that previous cannot hear. As a whole, listening is more comfortable and the sound is more noble. (My English is no good to explain in more detials)
By the way, modification is enjoying the result and also the process!

Elso Kwak 30th October 2003 06:51 AM

Masterclock
 
Hi ftp838,
Those 1 and 50 ppm are these jitterspecs or a frequency deviation spec?.
TCXO have generally better jitter specs but are harder to find and of course more expensive.
I would be curious to see how my clock compares to a precious TCXO. Can you disclose any source? I have given up knocking on crystal oscillator manufacturers doors......:headbash: :bawling:

ftp838 30th October 2003 08:16 AM

:o Hi, Elso, thanks for your response.
The TCXO I got it from a local (Chinese)XO manufacturer. If my understanding is correct, the seller claimed it is 1ppm/degree C accuracy. (Actually I do not have the machine to verify this but only by listening). This manufacturer cannot suppy XO of 16.9344 as he told me his old engineer resigned and the new engineers cannot produce a within tolerance XO. (As you may know talents in China is precious at the moment) But 24.576 is within spec.
He will further to try to make some for me. The price is terribly low. (If you interested in the source please let me know and I will clarify and e-mail more info' to you)

lok 1st November 2003 08:04 PM

which place to get the DC source
 
High FTP... I am now planning to modify my cdt15a also. Would you tell me in which place you get the power supply to the clock module?

Guido Tent 2nd November 2003 11:23 AM

Re: Masterclock
 
Quote:

Originally posted by Elso Kwak
Hi ftp838,
Those 1 and 50 ppm are these jitterspecs or a frequency deviation spec?.
TCXO have generally better jitter specs but are harder to find and of course more expensive.
I would be curious to see how my clock compares to a precious TCXO. Can you disclose any source? I have given up knocking on crystal oscillator manufacturers doors......:headbash: :bawling:

dear all,

The unit of jitter is time

TCXO have better VLF jitter spec (tomorrows freq is about the same as today) but that is not relevant for sound quality (as long as it is within redbook spec)

1 out of 50 "standard" canned oscs is worth listening, but needs improvement

Low noise power supply is key !

regards

wuffwaff 25th March 2004 09:12 AM

Hi,

can anyone tell me wich of the two master clocks in the CDT-15A has the greatest influence on sound quality?
A friend of mine want´s me to modify his player but doesn´t want to spent too much money. At the moment it´s not sounding very good on both solid state and tube output (grainy, not much air around the performers etc.)

thanks,

William

Guido Tent 25th March 2004 05:17 PM

Quote:

Originally posted by wuffwaff
Hi,

can anyone tell me wich of the two master clocks in the CDT-15A has the greatest influence on sound quality?
A friend of mine want´s me to modify his player but doesn´t want to spent too much money. At the moment it´s not sounding very good on both solid state and tube output (grainy, not much air around the performers etc.)

thanks,

William


the one that doesn't support the microcontroller

cheers

wuffwaff 25th March 2004 06:14 PM

Hi Guido,

for digital dummies you´ll need to be a bit more specific.

As far as I know the CS8420 is an upsampler chip with digital in/out, reclocking by external clock.

Quote from Phillips website: "SAA7327 (CD7 II) is a single chip combining the functions of a CD decoder, digital servo and bitstream DAC, especially designed for Video CD applications. The decoder/servo part is based on the SAA737x (CD7) and is software compatible with this design. Extra functions are controlled by use of ‘shadow’ registers."

So I would guess that the last chip before the DA conversion is the most important (CS8420).
Does this mean that jitter in the path before the reclocking is unimportant or that I have absolutely no idea how this cd player works?

Many thanks,

William


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