Increasing Capacitance

[riverrat373]

The tube amp project I'm working on calls for a 220 micro-farad 250 volt and a 100 micro-farad 250 volt electrolytic capacitors in the power circuit. Can I increase the capacitance of those capacitors? Would their be any advantage to increasing the capacitance? How much is too much?

[kheper]

In the link below is an equation for the (recommended) minimum filter capacitance in an amp.

http://tubes.nekhbet.com/#fil

Increasing the capacitance of the power supply will enhance bass and transient response. There is a point, however, where adding more will result in diminishing returns, and if you are using a tube rectifier, the cap directly off of it cannot exceed the maximum value in the spec sheet.

[Impmon]

The tube amp project I'm working on calls for a 220 micro-farad 250 volt and a 100 micro-farad 250 volt electrolytic capacitors in the power circuit. Can I increase the capacitance of those capacitors? Would their be any advantage to increasing the capacitance? How much is too much?

Need to see a schemo of the PS. It all depends on where those capacitors are connected, and what diodes are being used here. As for how much is too much, that's determined by the Isurge rating of the diodes. If the reservoir capacitor is too large, then the surge current will possibly exceed the diode Isurge spec.

It's especially problematic in regard to hollow state diodes. The 5U4GB has an Isurge= 1.0A per plate, and while that looks like a lot, it really isn't. For one project, I had an Isurge= 800mA with 34uF reservoir. This is why hollow state power supplies almost always include either LC or RC filters behind the reservoir capacitor: no other way to reduce the ripple to acceptable levels. (Even if you use Si diodes, you should still keep that capacitor small and use follow-up filtration. Your diodes might not mind the Isurge, but your vintage PTXs, and the new replicas such as the Hammond "Classic" series weren't designed with the much higher surge currents in mind, and just might.)

Bigger capacitors mean less ripple, but there comes a point where more produces less ans less benefit.