What determines your B+ filter capacitor size?

[thetragichero]

Marshall super lead (model 1959 100w) was released in 1965, when capacitance was relatively expensive, so they used *just enough* filtering. see also: a lot of older fender designs
the other amps are of considerably newer design where capacitance is plentiful. plus I'd imagine the design goals are considerably different. you wouldn't design an amp for, say, death metal by copying a tweed deluxe
the Marshall dual super lead I'm cannibalizing to made a bass amp had 2x 330uf as the first filter stage (and no supply choke)

[Steveo]

Phil,
JTM45 is tube rectified, all Marshall 100 W are diode rectified.

Steveo,
What Rivera do you have?

Roberto, It is the rivera ktre reverb. Thetragichero, your right I didnt know they were filtered that much.

[Roe]

I think that with the 100 watt Marshall they were still in the experimental stages of development as a company and they had 4 cans lined up there for the plates and screens and everyone was going bonkers over the amp. When they did the 200 watt amp the ultralinear transformer took away the screen filtering and allowed bigger caps for the plates. The 50uF thing was probably the best they could come up with at the time and if it ain’t broke, don’t fix it.

the filtering on the 100w marshalls varied from 32 to 100uf on the mains, 16 to 100uf on the screens, 16 to 100uf on the phase inverter and 16 to 50+50uf in the preamp. Most used 50, 50, 100, 50+50 though

[Roe]

Marshall super lead (model 1959 100w) was released in 1965, when capacitance was relatively expensive, so they used *just enough* filtering. see also: a lot of older fender designs
the other amps are of considerably newer design where capacitance is plentiful.

The superlead was introduced in 1967, the 1965-66 amps are super 100 amplifiers

[thetragichero]

i guess we could split hairs on that but in the context of the conversation 1965 is 1967 is probably 1973. we're talking filter caps so less than 5% tolerance is exceptional

[Roe]

i guess we could split hairs on that but in the context of the conversation 1965 is 1967 is probably 1973. we're talking filter caps so less than 5% tolerance is exceptional

Well, Marshall increased the filtering substantially, starting in 67. The mains went from 32uf to 50uf or even 100uf, whereas the screens went from 16uf to 50uf (or 100uf in rare cases).

[frankdrebin]

Marshall and Fender used what was available and at reasonable cost,so just enough...
There are specific values of capacitance per milliamp of current,and all guitar amp are lower than that,even the stiffest.

[roberto]

frankdrebin,

are you comparing guitar amps with F/A ratios given for SS Hi-Fi applications?

[TUBEDUDE]

On a related note, I've found that cap values are excessive on the P.I. and subsequent preamp supply nodes. Lowering cap values returns treble and life to the signal. Experiment!