Quote:
Originally Posted by red57strat
I've been thinking about messing with the filter caps since getting this amp. The schematic calls for 3 x 15uF, 3 x 22uF was used, a 5F3 Champ used 3 x 8uF and the original GA5 schematic calls for 1 x 20uF and 2 x 10uf.
Changing the first filter cap in my 5E3 clone to 30uF (from 16uF) tightened up the bass with the amp cranked quite a bit. Gerald Weber recommended not putting higher value filter caps in Champs. From what I've seen, filter cap values alter the looseness and tightness of an amp (as well as noise, of course) rather than tone.
It's a fairly cheap experiment to see how the amp responds to lower value filter caps.
I have a bunch of 16uF@475v caps including a Sprague Atom (will it fit in there???) that I can try in there. I'd be tempted to try 1 x 20uf and 2 x 10uF like the original schematic.
BTW, all of my recent 16uF Sprague Atoms measure 19uF on my capacitor meter.
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Don't forget that there are many versions on the GA-5 about. The one discussed here has 22x22x22 which is pretty standard these days. Champs are different and do benefit from a 16x8x8 configuration and sound better with the early Princeton's 32x8x8 setup. Most EL84 amps actually have an extra 20 to 50 cap with a small resistor (~150R) before the first 3 caps. See attached schematic.
Also from memory the GA-5 has no 1M resistor from the input to ground. That was an error in the early Gibson schematics that got carried forward.