apparently there is a sort of a bypass from what I've read.

The POT test mode of the Spider III.

What you gotta do is hold the TAP button while powering on the amp. this will get it into a POT test in which as the name says, it's going to test the knobs and if they are working properly. Also the speaker will be close to it's higher volume possible and there will be no effects or anything going on. just pure signal. you can probably regulate the volume via the POD itself

I don't know if this is entirely advisable though due to the fact that having the amp turn on so close to it's high volume..might brake something....I am waiting on my Floor POD Plus to arrive (a used one) to see what else we can do.

Other two options would be connecting to either the Cd-Aux of the Spider which produces a similar result to the POT test mode or just dial in a clean setting with all the dials at 12 o'clock and the effects turned off (including reverb)

Hope this helps!