Ack...does this mean my oscilloscope results are wrong?

[brad]

I'm using a function generator program on my PC to feed waveforms through my effects so I can take readings with my oscilloscope.  The signal goes from my soundcard, through a little Behringer mixer, and then to the effect...and I have the signal set to 0db on the mixer's meter.  So far, I've only been interested in seeing roughly how much boost is created by various stages of circuits, but this setup isn't going to show accurate representations of guitar signal clipping is it -because the output of the mixer would be much greater than the output of a guitar and thus drive the effect harder.

What can I do to set my test system up so that it accurately reflects a guitar/bass level signal?  Could I just set my scope so it shows a good trace of the direct output of my bass...and then connect the function generator and reduce its output until it looks comparable to where the level of the bass was?

[TELEFUNKON]

yes

[brad]

lol... 

[TELEFUNKON]

Could I just set my scope so it shows a good trace of the direct output of my bass...and then connect the function generator and reduce its output until it looks comparable to where the level of the bass was?

yes

[cd]

I'm sure Mark Hammer will chime in with one of his patented long treatises here, but in a nutshell: NO. 

First of all, there's really no such thing as a regular or comparable bass signal.  What are we talking about here - gentle thumb tapping, big finger popping?  Or for guitar, simple one note lead lines, big bashing chords?  The output of an instrument varies wildly.  OK OK I know what you're thinking, how about finding an AVERAGE and using that?  Like 100mV peak to peak?  That would get you in the ballpark, but remember what the output of a guitar/bass looks like: there's a sharp attack followed by a quick decay, with a potentially long sustain and release.  In other words, the output is not at a constant level, or what would be fed out of your function generator.  If you want to emulate the envelope of a guitar signal, you're going to need some sort of envelope generator to go along with your function generator.

That being said, a function generator is still useful if you want to look at ONE clipping threshold for a particular signal level, with a particular frequency - and in that sense, it's great to use to guage relative clipping types/levels. 

[gez]

If you're just trying to measure how much gain there is in a circuit, or how much headroom is available, ie what max peak-to-peak signal is possible, then what you're proposing is fine. 

Simple pot from output of function generator to ground will divide down the signal (couple wiper to your circuit).