Blue: to be perfectly honest, it wasn't my idea or finding. It came as a solution recommended in the Octaswitch manual on how to put pedals in the amps loop. I'm sure I would have figured it out on my own, but this way a quick look into the provided booklet saves ya a lot of thinking and time hahaha

Soooo, updates! I'm back with some results featuring pedal placement and happy to report the cabling has been sent out today, I already have a tracking number, fingers crossed I get the George L's this week!
Took my fuzz, my tuner, my wah and the underdrive and tried out different placements and combinations. Here's what I observed:
Wah and fuzz: So I went with the obvious combination of running my wah into the Hoof and I'm happy to report I have no oscillation issues. The two of them work together fine that way (apart from the poor sweep range of my cheap Crybaby). Swapped the whole thing around with the Hoof going into the wah. HELL NO. That way all the wah actually did was to work like a broken volume control. On the heel the fuzz became distant and quieter, on the toe position it gained volume back. I see how this might be cool for certain effects on songs but I won't use it that way. So wah into fuzz it is.
Tuner placement (buffering): So I tried the wah with the tuner before and after and even threw it in between wah and fuzz. If there was a difference it was a minimal one, although it seemed to me like the wah sounded better with the tuner after it. But then again the Octaswitch has a buffer button and therefor I don't think it really matters where I have my tuner. So I'll plan out the board first and decide then which placement I will go with. Plus I was using EMGs and I currently don't have a guitar with passives, so that might be a factor as well.
And now on to the really interessting part: Underdrive and Fuzz.
So I put the Underdrive before the Hoof. It worked exactly like rolling back your volume knob. It cleaned up. That's it. That way you can use it as a boost option, play a riff with the UD first in the chain and disengage it to solo. So probably my first train of thought was right here, the UD should always be first in the chain.
I reversed the whole thing. Guess what. Midrange cut. The UD does really work like you have a EQ there, it scooped the fuzz. Not a bad effect, but not what I was going for and the shift knob on the Hoof let's me control the midrange anyway.
Finally, the UD in the amps loop. This was interessting, it basically kept the sound the same coming from the preamp but cut back on volume. Boost option again!
So I guess I'm all set. The Underdrive is a really cool pedal with lots of options to use it. If you crank the midrange and the volume on it, it serves as a boost. If you cut back on the mids it cools down a distorted or crunchy amp. Put it after a fuzz and alter the amount of mids. Put it into your loop and suck out some volume. The Treble and Bass knobs leave additional room for adjustments. Well played Mad Professor! (Although the Pault Gilbert Detox was there first

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