Filter cap bleed resistor with 5AR4?

[Normster]

I think I've finally got my power supply design locked down for my 6V6 amp, except the bleeder resistor. PS is 300-0-300 -> 5AR4 -> JJ 50/50uF cap can -> 125C1A choke (between the 50uF cap sections). Since this is my first amp using a tube rectifier AND a multisection cap, I've been studying a few schematics that use a similar setup. None so far shows a bleeder resistor for the filter caps. Am I missing something?

[Ray Ivers]

Norm,

I'd recommend a 220K, 3W or 5W bleeder resistor for this design, across the first filter cap after the 5AR4. This will drain both caps down to less than 50V in about 10-15 seconds, while stealing only about a couple of mA from your PS.

I've seen bleeder resistors used for four primary purposes, although surely there are more:

a) to drain the filter caps on power-off
b) to equalize voltage across series-connected caps (in this usage they are also referred to as 'equalizing resistors')
c) to maintain a minimum current draw on the output of a choke-input filter
d) to load down a power supply's output to achieve some desired voltage.

IMO it's cool to look at a circuit you want to clone as a starting point only - not a final destination - as you're doing. A lot of times design decisions (like leaving out this bleeder resistor) were made purely on a mass-production cost-savings basis, a constraint the DIY'er should really be free of for the most part, at least for the smaller stuff.

It's a wonderful ride from "can this circuit be improved?" thru "how can I improve this circuit?" to "where's a blank sheet of paper?"

Ray

[Normster]

Thanks, Ray! That clears things up. I just wanted to make sure there wasn't something weird about a tube rectifier before I started throwing parts in the circuit.

[Enzo]

For example, what does Leo Fender care if the filter caps in the amp don't discharge right away? Why waste the expense of the part and the labor to install it to include a bleeder? It may be good practice to include it, but it doesn't add anything to the tone. Many amps are built with that sort of design philosophy.