Recommended Voltage/Resistance for audio lineout?

I've a bitbang based synth library that I have hooked up to a GH controller, and I need to know what the reccomended voltage/resistance is so I don't fry my computer when I plug it in for recording. Since arduino HIGH is 5V, I'm assuming my output right now is 5V?

You are not going to fry your soundcard at 5V, but you might overload a line-level input and get distortion. You WILL overload a mic input at 5V (but you won’t fry anything).

You may need a voltage divider (two resistors) or an audio taper pot (volume control) to knock-down the signal.

[u]Line Level[/u] for consumer equipment is around 1V RMS (3.4V peak-to peak). In the real world, it depends on the loudness of the recording, the volume control setting (if there is a volume control) and equipment variations.

A 5V digital signal through an RC high pass filter to block the DC will be 2.5V peak (5V peak-to-peak).

Basically, everything is designed so that outputs have plenty of output and inputs have plenty of gain so that an amplifier can always get to full power (with normal program material when the volume is turned-up). That means line-level outputs may be higher than the standard, and inputs may be more sensitive than the standard, and it’s assumed there is a volume control somewhere.

The input impedance will be 10K or more, so that shouldn’t put too much load on your output. Normal audio equipment would have line-output impedance around 1K or less, and line-input impedance will be 10K or more (100K is more typical).

Since arduino HIGH is 5V, I’m assuming my output right now is 5V?

I know NOTHING about GH (Guitar Hero?) controllers.