So, I finally got around to trying the RetroValves in a little 5 watt tube amp with tremolo and reverb. The amp has two 12ax7 tubes, one for premap and the other for tremolo/reverb - it's a piezo style reverb. In the preamp section general gain seemed about the same, but seemed kind of lifeless to me, but not horrible. The tremolo has a fixed intensity and the RetroValve made it way too intense - lol (good or bad, depending on what your looking for). With the reverb the RetroVerb didn't seem to make much difference.