I am "Vibroclonig" a 1971 Bandmaster Reverb and would like to know what values of filter caps I should use.
The original Bandmaster Reverb used (5) 20uf filter caps. In other posts, I've read that increasing the capacitance can increase the tightness of the bass, but on the website
http://www.lynx.bc.ca/~jc/fenderAmps.html, here's what he says,
"It is now time to discuss a mystery aspect of the power supply, Because electrolytic caps were costly way back (producing huge savings at the end of the year for a factory that cut costs right), today one can afford to replace the 70yF caps by 100uF bringing the resultant B+ capacity to a typical 50uF - this tightens up the low end a bit and gives the amp a slightly more solid feel without stiff'ing it ... installing overly large values is a bad idea as it can fry the power tranny slowly over time if streesed to high enough levels ... the preamp caps in general are not altered in value since the preamp is very sensitive to them and looses it's "dancing" quality if strapped down too hard ...
...namely the preamp power distribution network ... first the caps, if they're too small in value ghosting and motorboating effects may be induced - if they're too large the amp will sound really dead unless the tnwrok resistance level is high (as in Marshalls) ... in Fenders it is often a mistake to bring the cap values up from their 20-22uF values, some say 30-32uF is good too but generally speaking 50uF and higher filter caps are tone killers in amps that have otherwise the capacity to have the bias dance a little with the signal, a very subtle aspect of tube gear that is overlooked ... "
What values should I use to get that "big bottom" without losing tone?
Thanks,
Jim
The original Bandmaster Reverb used (5) 20uf filter caps. In other posts, I've read that increasing the capacitance can increase the tightness of the bass, but on the website
http://www.lynx.bc.ca/~jc/fenderAmps.html, here's what he says,
"It is now time to discuss a mystery aspect of the power supply, Because electrolytic caps were costly way back (producing huge savings at the end of the year for a factory that cut costs right), today one can afford to replace the 70yF caps by 100uF bringing the resultant B+ capacity to a typical 50uF - this tightens up the low end a bit and gives the amp a slightly more solid feel without stiff'ing it ... installing overly large values is a bad idea as it can fry the power tranny slowly over time if streesed to high enough levels ... the preamp caps in general are not altered in value since the preamp is very sensitive to them and looses it's "dancing" quality if strapped down too hard ...
...namely the preamp power distribution network ... first the caps, if they're too small in value ghosting and motorboating effects may be induced - if they're too large the amp will sound really dead unless the tnwrok resistance level is high (as in Marshalls) ... in Fenders it is often a mistake to bring the cap values up from their 20-22uF values, some say 30-32uF is good too but generally speaking 50uF and higher filter caps are tone killers in amps that have otherwise the capacity to have the bias dance a little with the signal, a very subtle aspect of tube gear that is overlooked ... "
What values should I use to get that "big bottom" without losing tone?
Thanks,
Jim
