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Many companies, the makers Soundblaster in particular, make a lot of soundcards that "fake" full duplex. True Full Duplex is the ability to record an input while playing back an output, and it requires two Digital / Analog converters. Where they only have one, I believe they fake it by lowering the sample rate and then devoting every other sample to the other signal (I could be wrong about this).

I own a Soundblaster LIve, which is one of these "faker" cards. I don't know whether to be unhappy.

Currently, if I record while playing back, the playback sounds normal (although it could be missing some superhigh partials and I might not notice), while the recorded input is totally mangled. Said mangling involves chopping it up so it sounds like I'm singing from behind a fan, and dropping the pitch a few octaves so I sound like a demon.

However, it might be correctible.

Signal quality is not very important to me. I'm using the thing for composing, not recording -- I just want to hear various ideas at the same time, so I can tell my band how to play something. Multitracking is very important -- like, the only important thing. [There's the wind-up. Now the pitch.]

Should I be grabbing a sound card with true full duplex, or can I cut the sample rates on the recording & playback (playback especially) so that recorded tracks beyond the 1st are recognizable?

Best tinkerings,
Jeff Brown
Comming for a recording guy, I would say that what you really want is the ability to do full duplex recording. Cutting the sample rate doesn't seem to be the right solution. If you lower the sample rate, than your only getting half of a lower sample rate.

Even with a fake duplex you should be able to get a decent sound though. There might be some issues with the drivers, they might not of gotten it compleatly right.

My advice to you is simple, play with the settings, try somethings, and if you can't get it to sound the way you want, upgrade. There are lots of greate audio I/Os out there, M-Audio makes some nice stuff in particular, so find something better. Just make sure if you want to be using it in linux, that you look around for compatibilty before you go spend the cash on a new card thats just going to do the same thing.
Thanks, Lest. It's great somebody knows what I'm talking about.

Yesterday I borrowed a Sound Blaster Audigy 2 ZS Platinum, which according to some accounts has true full duplex, although it's not advertised. I'm beginning to doubt that it does, though, because I get the identical problem -- tracks after the first sound like a demon talking behind a fan.

Are you sure that fake full duplex should be able to produce a recognizable sound? Because my card's certainly got fake full duplex capability; if you're right I'll hunt around some more.

But regarding that hunt: I don't see much to change. Half of the only parameters I can see to change are in KDE Control Center, under Sound -> Sound System -> Hardware. They are "use full duplex", "use a custom sampling rate", and "choose the quality (8 or 1 bits, or "default")". I've tried toggling all, without effect. The other half of the parameters I know to adjust are in KMix, and there's a zillion; I've tried toggling them individually, but if they interact much, I'm up factorial's creek without a diploma.

Terrified of boring my audience,
Jeff Brown


I had more than half an inkling to go buy an M-Audio as soon as I read your endorsement. However I must steel myself to this plan, which is to compose on the computer only to the point where I know how to score the piece, and then get it played. The only good a quality signal will do is I'll be tempted to produce from my computer, and I'll never get the band thing going.
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