Word Clock Generator

[Rochey]

that there is officially "post of the week" in my book.

 

[jdbakker]

Thanks Jim, and welcome.

It's a nice, straightforward digital design; no programmable logic, no microcontrollers. I'm not sure why they use the ACT logic gates in this configuartion as cable drivers; maybe they have some inside knowledge that each gate's driving impedance is about 150R (IME you're looking at closer to 15-20R for that technology), otherwise the output is not matched to either 75R or 50R. Perhaps a miscommunication between engineering and production: either use a single gate and the specified 51R1 termination, or have three gates with a 150..180R series resistor each in parallel.

It's not going to win any prizes for jitter. The signal passes through a lot of gates, and those HCT393s they use to divide the MCLK down are rather noisy. They spec an unqualified 20ns jitter. I might believe that if they have very low-noise crystal oscillators, but for either that TLC2932 PLL or the AES in through the CS8414 I'd expect several hundreds of ns worth.

All in all a nice design, with some cute mixed-signal tricks. The performance appears limited by the engineer's budget rather than his skills, which is always good to see. I wouldn't recommend DIYing this unit; due to economy of scale your build cost will easily exceed a second-hand or even new unit of equivalent specs.

JDB.

 

[mhelin]

[quote author="Jim Zuehsow"]You can find a complete word clock schematic at the following link. It is at the Symetrix site:

http://support.symetrixaudio.com/

Search for the GENx6 which is file #142

http://support.symetrixaudio.com/cgi-bin/symetrix.cfg/php/enduser/std_adp.php?p_faqid=83&p_created=1132273590&p_sid=kaCKGMri&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPSZwX3NvcnRfYnk9JnBfZ3JpZHNvcnQ9JnBfcm93X2NudD01MTEmcF9wcm9kcz0mcF9jYXRzPSZwX3B2PSZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX25sJnBfcGFnZT04&p_li=&p_topview=1[/quote]

OT: That long URL makes this thread unreadable (at least on my monitor with only 1280x1024 resolution).

 

[Jim Zuehsow]

Sorry about the long url. I just pasted it the way it was. Just click on it.

 

[Rochey]

I spent last night breaking down the circuit into bits I understand.

If anyone would like a "breakdown" of the circuit, then I can put it into a pdf if you like.

cheers

R

 

[Jim Zuehsow]

I had thought about building my own unit last year, but when I considered all that was involved in order to make a really high quality unit, I opted to just go out and buy a Big Ben. I was going to go with crystal oven references and PLL to generate clocks, but I realized that I really didn't have the proper equipment in my shop to tell what kind of jitter I would wind up with. I figured a company that dealt in this sort of equipment would have a product quit a bit better than what I would come up with.

 

[smallbutfine]

Hi guys,
I wanted to take a look into the GENx circuit and noticed the information is not available on the symmetix site anymore.
Would anyone be so kind and share the schematic again?

Thanks in advance and kind regards,
Martin

 

[Davo]

It's still up there... I just did a search and voila:
http://www.symetrixaudio.com/kb/GENx6_sch.pdf

cheers,
dave

 

[smallbutfine]

??? seems I am getting old. Thanks alot, that was fast, and sorry for bothering.

Kind regards,
Martin

 

[Davo]

;D