power supply caps

[sgunn]

was recently given a flood damaged kalamazoo30.looking it over someone has replaced caps with 2 20uf on mains and 2 68uf on preamp filters.is there any problem with that or reason for doing that? original had 4 20uf.

[Chuck H]

The bigger caps in the pre are probably an attempt to reduce hum. I've read elsewhere that these amps have hum issues. But that is more likely a grounding scheme problem than a lack of filtering. I don't like the tone of over filtered preamps myself but it won't hurt the amp. I can't find a schem, also important would be a layout, so I can't comment on how you might abate hum unless you are familiar with electronics and amps.

Is this Steve Gunner?

Chuck

[sgunn]

thanks don't know what happened to my reply yesterday. was just curious if there was some reason for bigger caps on the preamp.there' schematics elsewhere on the forum but was just a theoretical question.i've been called gunnar but i'm not steve gunner.haven't been in nw in years.i can see lead dress being a problem but have some other issues to deal with before i fire it up. if i don't like the sound i can put the bigger caps on the the b+ and the 20's on the pre. steve

[Chuck H]

Steve Gunner is a supporting stage musician for CCR. Not a guy I know here (in the PNW). I've been working with him on some amp designs so he's getting the bug fast and I expect he'll be tinkering with his own amps soon . The fact that your amp is flood damaged made me think Nashville. I know Gunner is well connected so I thought you might be him.

Good call on swapping the caps. Main filters are almost always better bigger. The exception being if your amp uses a rectifier tube. They can't handle the high voltage reserves of larger caps.