Impedance issues between amps with my new pedal build

[saison94]

Hey everyone, so I've been working on a cool pedal design using two different source signals run through a 741 summing amp. Sounds great coming out of my old cheap solid state sears amp from the 70s and the little bass amp i have, but for whatever reason the signal isn't getting through on my tube amp. if i crank it up to what would normally be unimaginably loud levels i can hear a distant gated sound of the effect, but that's it.

i've taken the pedal apart, breadboarded it, etc and still, nothing out of my tube amp. What could be the reason? from what i've read tube amps have a really high input impedance which, in theory, should support any input source. could it be something else other than impedance issues?

thanks for any help!

[saison94]

figured it out. needed a capacitor at the end of the sum amp to block AC. i'm assuming the tube amp i have is more sensitive to that sort of thing? could be the problem in the pedals from the other thread that didn't work...

[Paul Marossy]

Yeah, you need to watch out for those DC blocking caps. 

[CynicalMan]

Tube amps (for reasons of which I am unaware) are often built without blocking caps on the input. Your solid state and bass amps probably had them, and so your pedal's cap was redundant.