How Is Appropriate Size Determined For Filter Caps?

[David Root]

Personally I think that 1Hz rule could lead to overfiltering if applied unthinkingly, especially at the preamp end of the chain.

For a push-pull power end I select the reservoir cap so that the ripple on it is less than 10% of the B+, and usually nearer 5%. Screens and PI usually get about 20uF and preamps 16 down to 8 or so, as I almost always use a choke after the reservoir cap.

But then I`m not a fan of really stiff power supplies, at least not stiffer than in an early Dumble circuit. I admit some designs would properly call for more than these levels.

[rp]

I'll add that I found the smaller amps (Tweed Champs) benefit from the original low filtering, makes them sound fatter and more 3D, but speaker size, use - home, recording, gig mic'd, matter much here. Bigger vintage amps can benefit from a judicious filtering upgrade in the modern world. I prefer the 5E3 with 22, 22, 16 and a 120ma PT, keeps the mojo and a little more focused for modern playing. I prefer the JTM Marshall filtering of 32 straight across and even 50, or 50/32 on a Bassman. As said, you have to play with it, different strokes...