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Old 5th July 2004, 04:19 PM   #21
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BRSEL selects the crystal oscillator freq being used. When it is not connected and the cystal is 12.288 MHz, then a 256 fS will be 48 kHz sample rate. Pin 28 (CKSEL) must be low (gnd) for it to lock onto the input signal. Have you tryed 16 or 24 bit data format and 128 fS or 256 fS system clock? What is the crystal frequency?
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Old 5th July 2004, 05:33 PM   #22
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You can also connect pin 28 (CKSEL) to pin 27 (UNLOCK) so that it will go into PLL mode during unlock conditions.
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Old 5th July 2004, 09:36 PM   #23
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OK there im using a 12.288 mghz 20ppm crystal. SCF1 and SCF0 are both connected high, so the DIR is on 512fs for the system clock. I think Ill change this so I can use 96khz if the need arrises. BRSEL is open so yes 256fs crystal oscillator is the default of 48khz.

I am using I2S for the data transfer mode, I thought this best because I couldnt see obvious matches for the DIR and the PCM1798, is this not the best option?

CKSEL is grounded.

Should the chip auto detetect the incoming sample frequency?

Is something wrong with the way Ive got it wired up?

Cheers Matt.
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Old 5th July 2004, 10:04 PM   #24
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Setting the system clock to 256fs didnt do anything at all for the popping noise. It might have reduced how often it pops but I cant tell at the moment.
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Old 5th July 2004, 10:59 PM   #25
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Those were just some things to try to see if lower data and freq are affected by the layout. The DIR will auto detect and change sampling rates on the fly. Ensure the source is good.
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Old 6th July 2004, 11:20 AM   #26
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Actually lowering the frequency of the system clock to 256 did make a large difference to the popping, it hardly ever occurs now. So far I have not got it to lock onto a 44.1khz frequency from either an armcam alpha 8SE CDP or a TEAC VRDS T1 transport. It works in the application its required to work, but its a bit odd that it doesnt lock on, its just woking in the BRATE sample frequency. I shall fault find the next time the lid is off.

Now that the popping is cured I can enjoy the music more!

Cheers Matt
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Old 6th July 2004, 12:45 PM   #27
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You are driving your DAC with 48K from the Soundblaster ?

Are you playing CD's or mp3's that are at 44.1K ?

If so that means that you are using the Soundblaster top resample to 48K. I read that the internal resampling in that is quite poor, im interested cos I have one.

You might get even better sound with a more up to date card.

There might be a way to test this.
Rip your favourite track from CD.
Resample it using top quality software, EG Soundforge etc
Play the new 48K track which will now not be resampled by the Live card.
See if it sounds better. If all the above is true I think it would be.

If you think its better than the T1, I want one!

Any idea of parts cost excluding P/S and boards and box ?
Ie without getting samples.

Thanks,
Brian

ps Well done indeed.
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Old 6th July 2004, 01:52 PM   #28
lucpes is offline lucpes  Europe
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A better player would help, you can use foobar2000 from http://www.foobar2000.org/ , set it to resample to 48kHz (better than the Live!'s resampling) if you have a soundcard that does that anyway and use the Kernel Streaming output mode (make sure to install it when setting things up).
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Old 6th July 2004, 04:50 PM   #29
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Quote:
Originally posted by brianuk
You are driving your DAC with 48K from the Soundblaster ?

Are you playing CD's or <A TITLE="Click for more information about mp3" STYLE="text-decoration: none; border-bottom: medium solid green;" HREF="http://search.targetwords.com/u.search?x=5977|1||||mp3|AA1VDw">mp3</A>'s that are at 44.1K ?

If so that means that you are using the Soundblaster top resample to 48K. I read that the internal resampling in that is quite poor, im interested cos I have one.

You might get even better sound with a more up to date card.

There might be a way to test this.
Rip your favourite track from CD.
Resample it using top quality software, EG Soundforge etc
Play the new 48K track which will now not be resampled by the Live card.
See if it sounds better. If all the above is true I think it would be.

If you think its better than the T1, I want one!

Any idea of parts cost excluding P/S and boards and box ?
Ie without getting samples.

Thanks,
Brian

ps Well done indeed.

Quote:
Originally posted by lucpes
A better player would help, you can use foobar2000 from http://www.foobar2000.org/ , set it to resample to 48kHz (better than the Live!'s resampling) if you have a soundcard that does that anyway and use the Kernel Streaming output mode (make sure to install it when setting things up).
Im already there ive got my CD's ripped to the hard disk as wavs and I play back using foobar with the resampler to 48k using kernel streaming!

Parts..... well I spent 40 from browndog for the SSOP to DIP converters, PCB maybe 20 with all the chemicals but I bought a large number of developer and etchant as small amounts just cost WAAAY to much. So in a large quantity maybe half that for the PCB. I spent 25 at farnell and about the same at maplins, Probably about 100 give or take say 30 but I bought nice caps for the IV stage which are not cheap. Also opamps are not cheap, esp the OPA627's and AD797 in the IV stage. But considering this box outperforms a 500 albeit old, DAC with ease id say its worth it. If you already have some of the more expensive parts, opamps for IV and power supply and case you can do this for 100, less if you can make a SSOP PCB.
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Old 6th July 2004, 05:31 PM   #30
brianuk is offline brianuk  United Kingdom
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Thats a good link, thanks for that, very useful

Sounds like a good Dac for the money!
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