I use an Apple Powerbook laptop computer for my rig, both in my personal home studio and for my gigs and presentations. By using a Roland GI-20 to convert the guitar signal to MIDI and connecting it to my laptop via USB, I can use my Godin to play software instruments in applications like GarageBand and Logic, and to record MIDI information into a sequencer or music notation program. We can also take the guitar audio itself into the computer for digital signal processing (like adding chorus or reverb), and for this we'll need an audio interface.
When using a computer to process your guitar audio, you'll want to use a high-quality audio interface that has the right input impedance for guitar output. Popular audio interfaces use either the USB or FireWire (IEEE1394) standards. USB is a less expensive approach, but FireWire provides a more robust connection when using multiple audio channels. Two excellent FireWire choices are the Mark of the Unicorn (MOTU) 828 mkII, which I use in my studio, and the M-Audio FireWire 410, which I use when traveling on the road because it is small and light. Since I'm using a computer, I use software instruments, both for live performance and for backing tracks from my sequences. I also use the computer to process my live guitar audio, and to record as well. Here's how I set up my gear:
Godin Synth Access guitars have a standard 13-pin connector that may be used with most guitar-to-MIDI converters, as shown in figure 1:
Figure 1. The jack panel on a Godin Synth Access Guitar, Showing the 13-pin connector.
1. Connect the output from the Godin13-pin connector to the input of the Roland GI-20. This connector is on the far left of the GI-20's front panel, as shown in Figure 2:
Figure 2. The Roland GI-20
Figure 3 shows the guitar connected to the GI-20:
Figure 3. The Multiac SA Guitar connected to the GI-20 Guitar-to-MIDI Interface
Now when I play a note on my Godin Synth Access guitar, the GI-20 will very quickly identify the pitch and create a MIDI note-on command. This command will go to my laptop computer over the USB cable, so we'll next need to make that connection.
4. Connect a USB cable from the GI-20 to the computer. The USB port is on the back of the GI-20, using an "A" style connector. Plug the other end of the USB "B" connector into your computer. This connection will allow the notes I play on my guitar to be sent to the computer in MIDI format, so I can play software instruments and record into a sequencer or notation program.
Figure 4. The back panel of the GI-20, showing the USB connector on the far right.
5. Install the latest driver from Roland onto your computer, either from the supplied CD-ROM or by downloading from Roland's Internet site.
Next we'll want to connect the audio output from the GI-20 to the computer for processing and/or recording. The GI-20 passes the direct mono guitar output from the 13-pin GK cable to the "Guitar Out" 1/4" jack at the rear of the unit. See Figure 4.
6. Connect the Guitar Out from the GI-20 to the Mic/Instrument input on the front panel of the FireWire 410 (or other audio interface). Figure 5 shows this connection.
Figure 5. Connecting the guitar output from the GI-20 to the Audio Interface
7. Now we connect FireWire between the FireWire 410 and the computer. This sends the audio from the guitar to the computer.
8. The next step is to connect the audio from the FireWire 410 to your sound system. Now any sound made by your computer, either as a software instrument or as processed audio from the guitar will be present at the stereo outputs of the FireWire 410. The computer can act as a mixer to stereo, or you can use the individual outputs of the FieWire 410 (there are 8 analog outputs) and an external mixer. I use Logic to host the software instruments, process my guitar, record MIDI and Audio, and mix everything live. (It can also print scores and parts!) Figure 6 shows the final connection setup: