External DAC connected to S/PDIF output - please help - diyAudio
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Old 21st July 2004, 09:52 AM   #1
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Default External DAC connected to S/PDIF output - please help

Here is what I'm thinking about doing:

I have a very crummy soundboard, one of those with custom poor on-chip DACs/ADCs, and I'm thinking about connecting an external quality (or at least better) DAC to the S/PDIF output. Here are my questions concerning this:

1. Can this be done?
2. Is it worth doing? I'm not asking this in the "wouldn't buying a better souncard be cheaper/simpler" sense, but in the "would the sound quality improvement be worthwile" sense.
3. If the answer to 1 and 2 is "yes", what DAC do you recommend? Here is where the price factor enters the scene. To be frank I don't know what the prices are for reasonable quality DACs, and since I live in Romania, scratch that, make it some distant exotic country with very nice people, I will probably have to consider ordering the DAC dirrectly from source, and the delivery taxes may be not so small.

Many questions may come in time, if you will be kind enough to take the time to answer these Thank you in advance.
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Old 21st July 2004, 11:19 AM   #2
OliverD is offline OliverD  Germany
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Hey Mr. push_pull,

it will work the way you described.

Some caveats:

- The digital output signal should be plain S/PDIF, no mulitchannel / compressed format. You should be able to adjust this in your soundcard setup.

- Most soundcards heavily process the output signal in the digital domain and you cannot bypass this. The DSPs which are used have a crappy resolution and algorithms, so the quality of the digital signal might not be as good as you expect. For example, most soundcards resample to 48kHz no matter what the input is.

- The jitter performance won't be very good...

However, the sound quality will still be much better than the analog output of the soundcard!

As for the DAC, do a search for the keywords "non-oversampling", TDA1543, CS8412... Excellent sound for little money. And all chips DIP
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Old 21st July 2004, 11:49 AM   #3
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Quote:
Originally posted by OliverD - The digital output signal should be plain S/PDIF, no mulitchannel / compressed format. You should be able to adjust this in your soundcard setup.
As crummy as my soudcard is, I would expect it to be plain S/PDIF.

Quote:
Originally posted by OliverD - Most soundcards heavily process the output signal in the digital domain and you cannot bypass this. The DSPs which are used have a crappy resolution and algorithms, so the quality of the digital signal might not be as good as you expect. For example, most soundcards resample to 48kHz no matter what the input is.
Yes, this sucks

Quote:
Originally posted by OliverD - The jitter performance won't be very good...

However, the sound quality will still be much better than the analog output of the soundcard!
Well, no comment.

Quote:
Originally posted by OliverD As for the DAC, do a search for the keywords "non-oversampling", TDA1543, CS8412... Excellent sound for little money. And all chips DIP

I will do this, maybe they are avalaible even in Romania. And DIP is good I'm not afraid of SMD though, I've seen hand-made PCB's with SMDs.

And thanks for the reply.
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Old 21st July 2004, 12:34 PM   #4
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Other comments are also welcome!
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Old 21st July 2004, 01:17 PM   #5
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If you use Winamp(maybe XMMS too), try to configure most of the plugins to play 48k, so the sound card will not resample it and will give a much better sound quality.

Best sound quailty in winamp:

MP3/2/1 playing, can't resample, use MAD plugin, better sound.
WMA, can't do anything.
MIDI, use resampling and set it to 48k.
MOD player, stop using it, use BASS.dll MOD plugin(better sound) to 48k instead.
Vorbis, can't do anything.
MP4 Demuxer, can't do anything.
CD/LineIN, use digital input.
Wave, NSV, dshow : nothing.

Output, download the "Software Resampling Output plugin" from winamp.com . If you want to use less CPU, use sampladelic, which it's final revision is a beta.
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Old 21st July 2004, 01:33 PM   #6
MWP is offline MWP  Australia
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Quote:
Originally posted by DragonMaster
If you use Winamp(maybe XMMS too), try to configure most of the plugins to play 48k, so the sound card will not resample it and will give a much better sound quality.
A better idea.... use Foobar2000.

http://www.foobar2000.org/download.html
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Old 21st July 2004, 01:39 PM   #7
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OK, I will consider that, I'm sure a good Winamp plugin makes a way better resampling than my 5$ soundcard.

Edit: I will check foobar2000 too (you posted after me hitting "reply" and before "submit thread") Just trying to keep everybody happy
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Old 22nd July 2004, 07:45 AM   #8
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Hi Folks ! ;-)

A Soundcard with a very crappy Digitalout are cards with the ForteMedia FM801 chip. I don't know what they doing, but it sounds very bad, independent of the samplingrate :-(


Regards

Jobstens
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Old 22nd July 2004, 08:11 AM   #9
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Sorry for asking such a stupid question, but are S/PDIF and I2S the same thing? I'm looking for the S/PDIF spec, I tried the Philips site, Google, can't find anything.
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Old 22nd July 2004, 09:23 AM   #10
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Quote:
Originally posted by mr_push_pull
Sorry for asking such a stupid question, but are S/PDIF and I2S the same thing? I'm looking for the S/PDIF spec, I tried the Philips site, Google, can't find anything.
No, it isn't.

SPDIF (or AES-EBU or IEC958) is e.g. between CD-Player and DAT-Recorder. It is a serial signal with including clock and subcodeinformation.

I2S (or IIS) is a serial signal with seperate bit- and word-clock which contains only audio.

There are some chips that convert between this formats:
SPDIF -> I2S
YM3623 (old), DIR1701, DIR1703, CS8411/12

I2S -> SPDIF
DIT4096, DIT4192, CS8401/02/03/04

Both directions:
CS8420/27


Regards

Jobstens
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