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Old 12th December 2002, 10:10 PM   #11
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Quote:
Originally posted by dorkus
> 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.
Hi

In my humble opinion, they should be at the transmitting side, that is, if you only use one series resistor. Situation changes if you fully work with a characteristic system, but there is no need for that as long wiring is kept short.

Sony engineers are talented, but designing audio equipment requires a lot of skills, as most among us (including yself) find out in daily practice.......

enjoy
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Old 12th December 2002, 10:14 PM   #12
dorkus is offline dorkus  United States
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yes, the series resistors are near the HC04 chip, before the PCB traces to the DAC chips. i assume that's what you mean by transmitting side. i dunno if the values were chosen arbirtraily, or if the actually modelled the impedance of the board. would be impressed if it were the latter.

guido do you have a web page for your clock? how much is the module?
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Old 13th December 2002, 09:40 AM   #13
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Quote:
Originally posted by dorkus
yes, the series resistors are near the HC04 chip, before the PCB traces to the DAC chips. i assume that's what you mean by transmitting side. i dunno if the values were chosen arbirtraily, or if the actually modelled the impedance of the board. would be impressed if it were the latter.

guido do you have a web page for your clock? how much is the module?
Hi

Then the Sony engineers did the right trick. I myself see 47 to 100 ohm a s a right value to start with. If you choose a too high value, the slope of the 0/1 transition will be to low, which might lead to jitter.

The final impedance is a tradeoff between

- slope
- RF current reduction alongside the board

The slope obviously is important wrt jitter, the current amplitude and frequency are too (lees obvious)

Currents across the PCB yield voltage build-up in th egroundplane, which in turn leads to induced jitter at the receiving end as well.

Looking at average PCB designs, with thin traces (heavy traffic....) board trace impedance might be something between 100 and 200 ohms

As for the XO info: You may look at the site of my HK or USA distributors:

http://www.southernelectricaudio.com

http://www.southernelectricaudio.com

and look for XO or accesoires

all the best
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Old 13th December 2002, 09:59 AM   #14
jcarr is offline jcarr  United States
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The 74HCU04 is a hex inverter, yes? How about replacing it with something else?

I wouldn't suggest an AHC, but I find that the VHCs (74VHCU04) usually sound better than the HCs.
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Old 13th December 2002, 10:10 AM   #15
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Quote:
Originally posted by jcarr
The 74HCU04 is a hex inverter, yes? How about replacing it with something else?

I wouldn't suggest an AHC, but I find that the VHCs (74VHCU04) usually sound better than the HCs.
Hi

There are 2 issues

- the fact that inverters are paralleled
- the family of logic

I do not like parallelling inverters for several reasons, so always try to use only 1. If you want the non-plus-ultra, just use picogates !

Yes, you are right about VHC or HCU logic, it is better than HC, but has lower fanout: no free lunch !

enjoy
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Old 14th December 2002, 05:26 AM   #16
Art is offline Art
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Hi Guido,

How do you think about F family such as 74F74, 74F04? Any benefit from F family do you think about.

The HCU and VHC families are not available in my country. I have only HC and F to playing on but still looking for experiment.

Thanks in advance,
Art.
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Old 14th December 2002, 12:23 PM   #17
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Quote:
Originally posted by Art
Hi Guido,

How do you think about F family such as 74F74, 74F04? Any benefit from F family do you think about.

The HCU and VHC families are not available in my country. I have only HC and F to playing on but still looking for experiment.

Thanks in advance,
Art.
Hello Art, others,

I do not know what is inside the F type of logic. Once some time is free, I will have a look and carry out some measurements.

all the best,
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Old 14th December 2002, 10:31 PM   #18
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While my knowledge of digital audio is limited it seems like one thing that hasn't been mentioned is that most of the inverters that are run in parallel are for the six channel audio. If the CD player is going to be used for stereo the clock only needs to be sent to the DAC and Main board. I don't know if you would want an inveter for the line from the audio board to the main board, but that should be the only one you need...
Doug
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Old 14th December 2002, 10:36 PM   #19
dorkus is offline dorkus  United States
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i most definitely plan to use all 6 channels of my player! i enjoy multichannel SACD very much.
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Old 15th December 2002, 09:56 AM   #20
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Quote:
Originally posted by dcole
While my knowledge of digital audio is limited it seems like one thing that hasn't been mentioned is that most of the inverters that are run in parallel are for the six channel audio. If the CD player is going to be used for stereo the clock only needs to be sent to the DAC and Main board. I don't know if you would want an inveter for the line from the audio board to the main board, but that should be the only one you need...
Doug
Hi all

We need to discuss clock distribution here....

I'd suggest to

- Place the clock as close as possible to the DAC chips
- Directly feed the stereo channels
- Use 2 single inverter buffers (picogates) to drive the other 4 channels

Th measter clock here needs to feed 4 gates, which is feasable to my practice

best regards
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