Champ 12, help with switching and mods please!

[PurpleStrat]

I picked one up for $60 and decided it mas going to be a good amp to practice modding on. I had only dug in to my Valve Jr. so far. This amp is pretty complicated.

I could really use some help to understand how the Overdrive section works and how to use the triode powering the reverb as a boost. Also the bass is so over baring that I keep it on 1. Any other mod info, ideas or thoughts are very welcome!

Here is the schematic. http://www.ampwares.com/ffg/schem/champ_12_schem.gif

So far I took the 10k resistor in the tone stack out and added a 20k pot, changed the 1M Overdrive Volume pot to a 500k and took out the CD input, line out and head phone jacks. After tracing everthing I got it to work with all that pulled. Just had to put in one jumper for the speaker output.

Here is the pre amp schematic with everything pulled. http://i102.photobucket.com/albums/m..._12_schem2.gif

Here is a gut shot of what it looks like now.

[PurpleStrat]

[Robert M. Martinelli]

Hi,

as to the excessive "bass", I see the preamp has the cathodes partially bypassed by .68 microfarad capacitors, the first thing I would do would be to replace them with .33 or even .22 caps to shift the lower frequency response to a higher frequency.

To get some boost I would not touch the reverb section, but I would try to tinker with the gain stages to increase the gain a little on them, remember gains multiply ( e.g. if you raise the gain on both stages from, say, ten to twelve you're actually increasing gain from 100 to 144, which should be more than enough.... BTW these ore not the actual gains, just rough numbers to give you an idea ).

Hope this helps

Best regards

Bob