Never thought I would've used that combo, but I used them behind the main guitars (ABG Knucklehead) and it seems that they gave some nice support and body, and a tiny bit of bite to the otherwise a bit thin sounding guitars. Compare (there are some level changes, but you can still clearly hear the effect the muff guitars have):
without muff guitars and with muff guitars (and main guitars muted, muff guitars only)
Signalchain: Ibanez Artcore -> Boss NS2 -> Electro Harmonix Big Muff Pi -> Ibanez TS9 -> Peavey Windsor -> Harley Benton 2x12 w/ V30's -> Shure SM57
Settings on the Big Muff was Volume 3 (o clock), Tone 2 o clock, Sustain 9.30. I used the TS9 just to even out the nasty fizz from the muff and as a level adjustment, but it has a very small boost on the drive.
without muff guitars and with muff guitars (and main guitars muted, muff guitars only)
Signalchain: Ibanez Artcore -> Boss NS2 -> Electro Harmonix Big Muff Pi -> Ibanez TS9 -> Peavey Windsor -> Harley Benton 2x12 w/ V30's -> Shure SM57
Settings on the Big Muff was Volume 3 (o clock), Tone 2 o clock, Sustain 9.30. I used the TS9 just to even out the nasty fizz from the muff and as a level adjustment, but it has a very small boost on the drive.
