Sony SACD clock circuit - suggestions? - diyAudio
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Old 8th December 2002, 10:47 PM   #1
dorkus is offline dorkus  United States
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Default Sony SACD clock circuit - suggestions?

hi all,

after hacking up (then shorting out the power supply of) my Sony DVP-NS500V DVD/SACD player, i've moved on to modding my C222ES SACD changer. it has a much nicer layout that's more open to mods than the NS500V. i've got ideas for the analog stage but i'm wondering about the clock circuit... one nice thing is that Sony put the crystal right on the DAC/analog board, very close to the DACs, instead of on the digital board. however i'm not so sure about the oscillator circuit employed... take a look below. the hex inverter is used for the oscillator, as well as to feed three DSD1702 DAC's and the main digital board. i'm not sure how the jitter performance of this circuit is but i'm thinking it could be improved. suggestions?
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Old 8th December 2002, 10:56 PM   #2
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Guido Tent/Elso Kwak clock.
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Old 12th December 2002, 05:53 PM   #3
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Default Re: Sony SACD clock circuit - suggestions?

Quote:
Originally posted by dorkus
hi all,

after hacking up (then shorting out the power supply of) my Sony DVP-NS500V DVD/SACD player, i've moved on to modding my C222ES SACD changer. it has a much nicer layout that's more open to mods than the NS500V. i've got ideas for the analog stage but i'm wondering about the clock circuit... one nice thing is that Sony put the crystal right on the DAC/analog board, very close to the DACs, instead of on the digital board. however i'm not so sure about the oscillator circuit employed... take a look below. the hex inverter is used for the oscillator, as well as to feed three DSD1702 DAC's and the main digital board. i'm not sure how the jitter performance of this circuit is but i'm thinking it could be improved. suggestions?
Yuck !

TOO many inverters in the circuit, and they are in parallel .....

Yes, the crystal may be where it should be, the design however does not have low jitter in mind.

Get rid of them, as much as possible, and use the lowest nr of gates possible to distribute the clock

I myself never encountered an 04 based clock circuit that measured / sounded well, so throw it out

succes
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Old 12th December 2002, 05:54 PM   #4
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hi guido,

what is your clock circuit? is it similar to Elso's?

cheers,
marc
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Old 12th December 2002, 05:59 PM   #5
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Quote:
Originally posted by dorkus
hi guido,

what is your clock circuit? is it similar to Elso's?

cheers,
marc
Marc

My circuit differs from Elso's. I supply a canned module (DIL8 based), which only needs 5V (low noise please) and puts out a neat square wave, measured jitter 3 ps (rms, 3-sigma).

I also have complete boards with power supply and SPDIF reclocker available

all the best
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Old 12th December 2002, 06:08 PM   #6
dorkus is offline dorkus  United States
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how is the current drive of your clock chip? in this application the clock will need to drive at least 4 chips.
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Old 12th December 2002, 07:52 PM   #7
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Just to let you know, Dorkus, I've got Guido's clock in my 775 Sony, which is the same circuit, and it is terrific. Cheap, too. - Pat
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Old 12th December 2002, 09:21 PM   #8
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I would leave IC304 in place for buffering clocks to distant / noisy circuitry, but wire the replacement oscillator's output directly to the DAC if possible. IC304 is inverting, so if you remove C303, R323 and X301, then inject your clock into IC304 pin 1, this will pretty closely preserve the clock timings and hopefully prevent problems. You can simply lift the IC304 pins which are outputs to the DACs, and instead wire those pads directly to the oscillator. A canned oscillator will probably do a fine job to test if it will work, and then I'd move to a more sophisticated oscillator later.
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Old 12th December 2002, 09:58 PM   #9
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Quote:
Originally posted by hifiZen
I would leave IC304 in place for buffering clocks to distant / noisy circuitry, but wire the replacement oscillator's output directly to the DAC if possible. IC304 is inverting, so if you remove C303, R323 and X301, then inject your clock into IC304 pin 1, this will pretty closely preserve the clock timings and hopefully prevent problems. You can simply lift the IC304 pins which are outputs to the DACs, and instead wire those pads directly to the oscillator. A canned oscillator will probably do a fine job to test if it will work, and then I'd move to a more sophisticated oscillator later.
My oscillators drive 15 pF, that is 3 or 4 gates, assumed little wiring capacitance is present.

Good suggestion, directly drive the DAC where conversion takes place, distribute other clocked gates using buffers. I always advise the use of series resitors, by the way.

My oscillator is not an off the shelf type, though it may look like this.

It has been selected among over 20 oscillators. After I measured all of them, and listened to them too, I selected this one, went to the manufactuer, sat down and talked about improvements. Once these where caried out I was really satisfied, as all of my customers are.

best regards
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Old 12th December 2002, 10:05 PM   #10
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> I always advise the use of series resitors, by the way.

yes, good to damp the lines. here is one area where Sony appears to have really done their homework - you can't see them in the schematic but there are series resistors before all the clock lines to the DACs, and they are different values depending on the length of the line - 22, 33, and 47 ohms for the shortest to longest PCB traces. a nice touch.

as much as we scoff at the mass-market nature of Sony products, i have to admit there is a lot of solid engineering behind them (Nelson Pass has mentioned this himself). in particular, the diagnostic modes on the player are unbelievable - it's like The Terminator or something.
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