Comments on: Linux-based audio toys

By: bryguypgh

bryguypgh — Mon, 04 Oct 2004 09:36:19 +0000

I’m using an M-Audio Delta 44 PCI card (4in/4out balanced or unbalanced 1/4″ jacks) with very good results under Planetccrma, and if you play with the jack paramaters you really can get the latency down under 5ms, suitable for using as a real-time guitar or mic effect. Jack-rack works like an effects rack, although the quality of the included effects in the version I’m using (which I admit is almost a year old) is hit and miss.

I’m curious about the USB setups – does going over the serial bus introduce extra latency/bandwidth limitations? What if you share it with a mouse/keyboard/whatever?

By: Rich

Rich — Wed, 17 Mar 2004 12:27:16 +0000

Yeah, but when you record a bass direct, you go through a DI box (like this) to match impedances. In any case, it looks like I’m going to have to buy or borrow some kit to make this all work. I’ll probably just go cheap PC or karaoke mic to begin with, and maybe solder up an xlr-to-1/8″ cable to use the DI on my good bass amp.

By: genericus

genericus — Wed, 17 Mar 2004 12:08:29 +0000

I don’t know about the math.

Bass is commonly recorded direct (though usually well-compressed). Guitars tend to not be recorded direct because they sound like ass that way, especially if you’re running through a distortion pedal.
It is not preferred way, and you certainly would not want to record this way ‘for keeps’, but it should do in a pinch if you need to record some ideas in.

Also: strike the whole audio driver thing. Some smrt monkey decompiled the drivers for the unused 8-channel audio card currently sitting on my shelf. When I find some time (HA!) I may have to fiddle with this stuff…

By: Rich

Rich — Wed, 17 Mar 2004 12:02:34 +0000

Woops, missed the second part of your comment, sorry! USB audio seems to have taken care of the "get the interface out of the noise-machine" solution for Linux. The kit from M-Audio comes highly recommended, and I know that a couple of people on the PlanetCCRMA mailing lists use the Quattro. Basically, though, anything that complies with the USB Audio Class Definition should work.

By: Rich

Rich — Wed, 17 Mar 2004 11:50:33 +0000

Hrm, you sure? Levels and impedances don’t seem to match up in my head. Guitar pickups have a huge impedance (somewhere in the range of 500Kohm!), so without a matching impedance on the other end it’s going to come across quiet and dull, since the soundcard side is going to be somewhere around 500 ohms. (That’s the same reason you wouldn’t plug a guitar straight into a board — the DI box handles impedance matching primarily and gain a far second.)

I might be able to get away with it on the bass because it’s got an active preamp on board, but even then I suspect it’s designed to provide the sort of load that a passive pickup would provide.

It’s been a long time though so I could be misremembering or miscalculating. Or am I stuck thinking about power transfer instead of voltage transfer?

By: genericus

genericus — Wed, 17 Mar 2004 11:27:55 +0000

Radio Shack (or canadian equivalent!)1/4″mono to 1/8″ mono adapter.
Plug instruments directly in (no amp).
Its easier to get away with this on the bass than on the guitar.
You can plug the output of any stompbox you have directly in this way also, but you should not plug the output of any amp into your comp. If your guitar amp has an effects loop you could probably plug the ’send’ into the comp safely, as the signal has been amplified at that point, but not to the point of being ready to drive speakers.

My whole problem with Linux as a music platform is the interface. If you find a good audio card that is Linux-friendly, let me know!