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Old 4th November 2008, 01:44 PM   #1
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Default Tapping master clock

Well, I'v been searching google and the forums for about 2 weeks or so trying to learn the basics on how dacs work and communicate with a source. But I can't seem to find any information on how to tap an spdif out from a dac (In my case a tda1541) so that i can feed the signal into my M-audio Firewire. The M-audio can lock onto the signal, becoming the slave, and the dac would then be the master. This would reduce jitter substantially. At least this is my limited understanding of the whole thing Any help would be appreciated!

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Dave
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Old 4th November 2008, 11:31 PM   #2
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Here are some pics of the dac, and the schematics

http://www.analogmetric.com/store/ga...id=194&img=318
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Old 5th November 2008, 06:31 AM   #3
amc184 is offline amc184  New Zealand
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What you have asked doesn't really make any sense. Are you trying to slave the digital source to the DACs clock? If that's what you meant, then yes, it normally would be a good idea.

However, your DAC is already running on its own separate clock independent to that of the source (your firewire). This system makes your DAC more or less immune to the source, but has a drawback in that the reciever (CS8412) must repeat or drop samples if the DAC and source clocks are even slightly different (which they will be).

To counter this disadvantage you can synchronize the source and DAC word clocks with the DAC as a master, which your source might allow (what model of Firewire do you have?).

If your source does allow slaving to a work clock (or sync, as it is sometimes called), then you can tap, buffer and drive the signal back to the source.
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Old 5th November 2008, 01:30 PM   #4
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Thanks for the reply! Yes I am trying to slave the digital source to the DACs clock , I just didn't explain it very well. The firewire model is the M Audio Firewire Audiophile. The more I learn about clocks, The more I realize how MUCH there is to learn. It's quite daunting.
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Old 5th November 2008, 08:37 PM   #5
amc184 is offline amc184  New Zealand
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Unfortunately your source doesn't support slaving to an external clock. Unless you want to do a lot more research and some serious modification, there's not much you can do.

Looks like a nice DAC kit you bought though. Have you tried removing and bypassing the SAA7220? That's one easy mod to get you started that might give you a bit of improvement.
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Old 6th November 2008, 02:07 AM   #6
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buy an old Squeezebox 2 and slave it to your tda1541a dac like this....

synchronous reclocking project
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Cheers ~ Mike
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Old 6th November 2008, 02:09 AM   #7
amc184 is offline amc184  New Zealand
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habsrock93 PMed me a message saying it was a shame that in couldn't be slaved, and that he saw that there was a sync option in the control software. The manual had this to say about that option:

Quote:
Sync Source – This field allows you to choose between the FireWire Audiophile’s internal clock and an external clock source. Internal selects the incoming clock fromthe FireWire bus as set by your audio software. Use external when you wish to record from the S/PDIF inputs, or otherwise lock to the sample rate from an external S/PDIF source.
This 'sync' option refers to which clock the FireWire uses when receiving digital audio via the S/P DIF input, either the recovered S/P DIF clock or its own internal clock. Nothing to do with the output unfortunately.

Also, another thing I would check it that the FireWire source is using a 44.1kHz sample rate. Some computer sources default to 48kHz, and since your DAC expects 44.1kHz sampled audio, and won't adjust, sending it 48kHz sampled audio might degrade performance.

Anton

PS: It is probably better to say things in the thread rather than PM, if only so that people with a similar question might be helped by reading this. And you should definitely try the SAA7220 bypass mod.
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Old 6th November 2008, 02:45 AM   #8
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Thats a good point. In the future I will post to the fourm. Thanks for clearing my confusion up (even though it's not what i wanted to hear ) I'll try the SAA7220 mod and post some pics, sadly it's going to be awhile before i can try the squeezebox out. There is not enough time in the day!

Thanks for the replys


Dave
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Old 7th November 2008, 04:42 AM   #9
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Does anyone know of any pc source that allows slaving to an external clock?

Thanks

Dave
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Old 7th November 2008, 06:41 AM   #10
amc184 is offline amc184  New Zealand
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Generally you'd be looking at pro-audio type gear to do that. Check out RME.
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