My first DAC hurrah.

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5th element

5th element

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Joined 2002
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.
 
5th element

5th element

Member
Joined 2002
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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brianuk

Member
Joined 2004
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! :D

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

Thanks,
Brian

ps Well done indeed.
 
5th element

5th element

Member
Joined 2002
brianuk said:
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! :D

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

Thanks,
Brian

ps Well done indeed.
Click to expand...


lucpes said:
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).
Click to expand...

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.
 
L

lucpes

Member
Joined 2003
pburke said:
woudn't it be better to use a sound card that works at 44.1kHz natively and ignore all the resampling?


Peter
Click to expand...

You mean a card that plays 44.1 without resampling :)

IMO a better transport (better soundcard in this case) would help in most cases and one may find audible differences between better cards/cheap cards/onboard (due to jitter amount on SPDIF out) rather stunning. So far it's been a general consensus regarding positive experiences using M-Audio, RME cards or possibly the new EMU 1212M marketed under Creative name.
 
5th element

5th element

Member
Joined 2002
Would another option be to get the I2S signal from the output of the EMU10K chip and make your own SPDIF output with low jitter? or is this asking for trouble? Kinda like an opposite DIR1703. I have been thinking about getting a better soundcard but thats only after several other things I wanna get first.

But the thing is how much improvement are we talking about here; from SBLive to Maudio - the TEAC VRDS T1 is meant to be a pretty good transport and if a £27 soundcard albeit with the data on the harddisk, sounds better, MUCH better this was no small difference. Then how much better can it get? I can hear vast amounts of detail in the sound, every little percussive flicker, vocal reflections from the environment natural or otherwise. Multiple voices or instruments are wonderfully separated making the sound really clear. I dont doubt that a better soundcard could sound better, but HOW much better is the question. All I really want one for is the SPDIF output, paying more gets you better opamps and DACs on the output stage, which im not interested in at all. One thing I would miss is the EMU10K chip and the KXdrivers on the SBlive. Does any specialist audio company make a high quality SPDIF output for a computer without anything else besides the digiout?
 
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lucpes

Member
Joined 2003
At least in the <$200 range no one bothers to go beyond mainstream sigma-delta AKM DACs and NE5532s. An M-Audio Revolution uses the same digital output circuitry (75ohm, transformer coupled) as other M-Audio cards and costs around $100 - it's a best buy if you want to go digital for music / or analog out for Home Theater use.

Best bet would be to try to 'loan' a better card for testing and see if there's any difference.

PS. There's no reason why you cannot fool around a bit with using better capacitors/bypass the existing ones for decoupling (clock supply/ICs in the digital path of the SB Live! :D ). Rubycon ZA low esr caps are small in size & fit like a charm for this purpose, albeit a bit on the expensive side from Farnell.

To desolder caps & clean trough-holes effectively and not ruin the board (I managed to do that by not using this method) due to hard to heat ground plane, carefully pull the existing cap out without using desolder pump, heat the through-hole on one side then quickly move to the other side & heat while applying the desoldering pump on the side where you first heated. All solder should come out in 5 seconds at most this way without any damage.

And regarding playing wavs from the HDD there's absolutely no reason not to compress those using lossless compression (ape/flac). Should save you some space - see my post in this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=32506
 
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