diodes before plate load

[alexg]

I have seen some circuits of tube amp and preamps, mostly from Japanese sites that uses a diode in between the PSU and the plate load.

Can somebody please explain to this tube newbie the purpose of the diode in that part of the circuit?

 

[Allen Wright]

There is absolutely NO reason to do this - unless there is a decoupling cap on the powersupply line that is after the diode - the diode then is acting as a "decoupler" so that ripple on the main supply from heavy load current demands doesn't affect the circuit being isolated.

Make sense?

Regards, Allen

 

[alexg]

Thanks, that makes a lot of sense.