Why do some pedals behave this way with my amp?

[renehawk]

Some overdrive pedals don't mesh well with my 18 watt TMB. The Mad Professor Sweet Honey Overdrive, Keeley Red Dirt Germanium, and any boost sound great with it. However, the Fulltone OCD, Keeley 1962, and Catalinbread Dirty Little Secret clash, creating an unpleasant, overly clipped sound. Is it a given that certain pedals just won't suit specific amps? Why do some pedals behave this way with my amp? I attempted to modify the sound by increasing the 500uf capacitor to 1000uf, but it only made the sound harsher, without a notable improvement.

[JMPGuitars]

Which TMB version did you build?

Do the pedals work at all? Can you turn the gain down on the pedal and it sounds good, or is it always bad?