Computer as guitar FX box?

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Metaxy

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Is it possible to use a computer as a guitar effects box? Let's ignore the whole latency problem, I'm talking about getting a signal through here.

There's the normal method of using a preamp to convert a guitar signal into something friendly without the amp->mic system; this of course changes the impedence on the signal to something good for a sound card line in, or headphones, or a stereo, or what have you.. But what I want to do is put the signal through my computer, possibly alter it in realtime with softsynths and the like (phaser, eq, etc.), and then pass it through to the line out at the same strength it came in.

Is there any special way to do this or will just plugging a guitar into an in and an amp into the out do it fine? I've heard both that plugging a guitar into your sound card can have far too weak a signal, or could ruin your soundcard from being too loud.
 
See if I understand well what you want do... You want to plug your guitar directly into your sound card, then process the signal with effect simulation, and whether record, or take the sound out to an amp.
If that's it, then it's all possible. Plug your guitar is no problem.
There are quite a lot of software that can process the signal, from free software to professional/expensive software. It's more or less VST-based. VST is like a sort of plugin that needs a host. Let's take an example, you can use a software called "chainer", when you run it directly, it is like an empty rack. Then you need to fill up the rack with amp-simulation, effect-simulation ; there are loads!
If your question is"how about the sound/quality ?", some people get something quite good out of that solution ... me I can't get anywhere (PC too old I guess! Or maybe the soundcard and speakers not good enough.).

So you can get for free a complete amp-simulation...but you need your PC to up to speed !
Plus you can use the thing to record that and do multitracking and things... it can be free as well...there you need your PC to be really up to it!
 
Yes, you can do this. It would be more than a pain in the ass to deal with live and probably not worth it, but it is definitely possible. Actually I read somewhere that Radiohead does this for a certain guitar effect they use live. One of the guitarists splits his signal of to a mac and uses it to process his guitar.

All you need are two good DI boxes and a decent sound card like an M-audio audiophile. The DI box converts your unbalanced guitar signal to balanced line level so you can then run it through your soundcard into the computer. Then you come out of your soundcard and backward into another DI box. This DI will convert your signal back down to the correct impedance to drive a guitar amp; I DI with variable impedance like Reamp even works better. No you can plug this right into your guitar amp. Note that this will take some of the load off of your pickups and in order to compensate you could buy an expensive DI with a buffer, but the pickup loading issue isn't that big of a deal, and it works fine without it.
 
i do it all the time. i route my guitar signal through a small mixer and an echo souncard and use the fx monitoring in samplitude. i suppose it doesn't matter which soundcard or software you use just as long as they enable ASIO drivers. with my set up i have a latency of 5 milliseconds, too low to notice when you're playing.
 
bzhGuitar said:
See if I understand well what you want do... You want to plug your guitar directly into your sound card, then process the signal with effect simulation, and whether record, or take the sound out to an amp.
Click to expand...

Well, I already use a software preamp/amp sim (USB based) called GuitarPort. It's nice but I can't get a decent tone out of it and I like physical amps better. (Don't take my word for it, a lot of people really like it). I meant to say not to record it, but to send it out to a guitar amp, not a normal amp.

noiseportrait said:
Yes, you can do this. It would be more than a pain in the ass to deal with live and probably not worth it, but it is definitely possible. Actually I read somewhere that Radiohead does this for a certain guitar effect they use live. One of the guitarists splits his signal of to a mac and uses it to process his guitar.
Click to expand...

You're right, it's the song Go to Sleep, he wrote a program with a tech to randomly interrupt his signal so it sounds like Adrian Belew-style modem noise (doesn't have the chops to make it himself, eh? ;) ). You can't really hear it in the studio version. It's pretty cool. Because it's so random-sounding the latency doesn't really matter.

I've always wondered if that effect was done on the way to the amp, or afterwards, between the mic and the PA system. Whenever I get to see RH live I'm gonna try to get a a good look at Jonny's wires when they play Go to Sleep, good reminder.
 
noiseportrait said:
All you need are two good DI boxes and a decent sound card like an M-audio audiophile. The DI box converts your unbalanced guitar signal to balanced line level so you can then run it through your soundcard into the computer. Then you come out of your soundcard and backward into another DI box. This DI will convert your signal back down to the correct impedance to drive a guitar amp;
Click to expand...

DI's convert instrument or line level to mic level. They don't convert instrument or mic to line. That's what a preamp does.

The best signal path would be
Instrument to DI and/or Preamp then soundcard.

Going out you would take the line level signal and run it through the Reamp box. You could use a DI on the output if that is all you had but the gain will be pretty low. If you don't use anything the gain will be very high but you can turn down the signal. This still doesn't correct the impedance mismatch and can affect your tone. Since you will be going through a computer I'll assume tone isn't that important.

If your amp has effects send/returns they would probably work best.
 
TexRoadkill said:
DI's convert instrument or line level to mic level. They don't convert instrument or mic to line. That's what a preamp does.

The best signal path would be
Instrument to DI and/or Preamp then soundcard.

Going out you would take the line level signal and run it through the Reamp box. You could use a DI on the output if that is all you had but the gain will be pretty low. If you don't use anything the gain will be very high but you can turn down the signal. This still doesn't correct the impedance mismatch and can affect your tone. Since you will be going through a computer I'll assume tone isn't that important.

If your amp has effects send/returns they would probably work best.
Click to expand...
I actually care a lot about tone, everything I try right now sounds like classic rock or metal, so part of the reason I want to use a computer is so I can try lots of subtle stuff to get something I don't hate. It makes me wonder what kind of engineering tricks are used in modern music to make the guitars sound so much fresher and different when it's the same gear they were using in the 70's. This is one thing I'm trying.
 
Well, my expieriances with computer amp modeling haven't been too great, but, there are a plethora of plugins out there, so I'm sure there's gotta be something good.

I'd suggest preamping (via preamp out or effects loop, NOT headphone or external speaker out, obviously), going into your computer, and then out to a power amp. Now, your preamp is going to affect your tone, so if you're doing amp modeling you'll want to find a preamp that effects your tone as little as possible. When I did this sorta thing, I used a Peavey backstage 30. It has a preamp out, and a good range of volume control for the preamp out, without affecting the tone much at all.

So after you get a good preamp, find a good amp modeler on your computer and a program that'll model real time, and then go from your computer to probably a power amp. If you go to another guitar amp, that amp will once again affect your tone, and then you'll probably never end up getting the tone you want (also, having too much preampage and preamping a preamp tends to distort/create some very bad tone). Anyway, point is, power amp is the way to go.

Alternatively, if you just want your computer to handle effects, then you should be able to just use your effects loop on your amp.

Hope this helps!
 
I've made some progress on this front - already got the M-Audio DMP3 ordered, which supports instrument-level input and is good for getting your signal into a line-level input rather cleanly for its price.

Next question is, in order to get my signal back out, is it important to have guitar-level impedence (by using tools like the Reamp or the Radial X-Amp), or can I just put the output volume down and it'll be fine?
 
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