spdif problem

[dobro]

I bought a spdif add-on from Gadgetlabs shortly before they breathed their last, and I've never been able to get it working properly. When I run a loop test (one cable running from spidf out to spidf in), I'm able to record copies of existing tracks, but there's loads of pops and clicks on the new track.

I've enabled DMA, and I've tried different buffer settings suggested by Cool Edit. I'm using the soundcard clock (recommended) and sample and bit rates match for all settings. I'm using the proper type of cable.

I've heard that pops and clicks in digital transfers commonly arise out of synching problems. True? Can anybody suggest anything?

 

[tubedude]

I've heard that running s/pdif without a clock will force the clock signal onto the s/pdif line, and that it can cause uglies. Can't confirm, just a rumor.

 

[Track Rat]

The clock information is embedded in the S/PDIF signal itself. As far as the clicks are concerned, it sounds like a master/ slave issue. When you're recording into the computer from an external S/PDIF source, the computer has to be set as the slave with the incoming digital signal as the timing master. All the other parameters should also match up between sourse and recorder like bit depth and sample rate but the pops and clicks sound like the recorder don't know who's boss.

 

[dobro]

Okay, I'll focus on clock and master/slave issues - thanks dude and rat.

I know how to make the soundcard the master, and I know how to make my outboard digital gear the master, but is there a clock anywhere else in the computer that I have to set as slave? I've only got the one soundcard. Is that the only clock in the system?

Small detail: how do you pronounce S/PDIF? I always say 'spidif', because I live in Singapore and have only ever heard one other person say it, and I didn't believe him.

 

[Riegs]

dobro,

just emailed you about it, but unfortunately i know even less than you do. i have an article in my guitar player magazine on the whole thing; it may not help, but i'll scan it if you'd like. creative labs (i use a soundblaster live) have been about as helpful as, well.. they haven't been the least bit helpful. "are you using the right cable? have you installed our latest drivers?"

also, i heard it's pronounced as "spee deef". i'll keep calling it "spidiff" myself at less risk of sounding like a moron in case the situation arises where it comes up in conversation.

good luck to ya,

 

[dobro]

dobro confessed to spdif he loved it
spdif said dobro you can go shove it
all of your brains are down in your cock
you don't even know where to locate your clock

Track Rat - if you read this, there's one thing I don't understand. When I do a loop test (spdif in and out to the computer, playing back and recording to itself) I get loads of clicks and pops. How can it be a clock issue if it's its own clock?

 

[Senor Cactus]

dobro confessed to spdif he loved it
spdif said dobro you can go shove it
all of your brains are down in your cock
you don't even know where to locate your clock

Nice rhymes.

Are this clicks and pops evenly spaced? If there is a definite even pattern to them then it's got to be a clock issue. Have you located anything in your soundcard settings that deals with clock source?
Have you tried to record anything with spdif from an external device? If so, does it work?

Another possibility: how hot is the signal on the audio you're playing? I've had problems with levels being too high in spdif recording. It recorded at a much higher level than it played at. If this is the case, some of those pops might be clips.

 

[dobro]

Cactus - the clicks and pops are *not* evenly spaced, and for what's it's worth, each click or pop appears either above or below the center line of the waveform, not both.

As for level: the level's fine. In a loop test like I've been doing, you're recording a copy of something you've already recorded before - the level of the copy is the same as the level of the original.

Thanks for your ideas - it is, indeed, time to start experimenting. It can't be that difficult to figure out - loads of people make this work all the time. It's the people who have had the same problem as me I'm hoping to attract.