Ampeg B25....30uF/600V caps

[soundguruman]

It has everything to do with it, because the poster just told me that there was no such thing as a 10,000uf cap in a tube amp, that's wrong.
And if HiFi solid state amp can have 10-20Kuf caps in power supply (which they do frequently) I can have the same in my tube amps, no difference.

This began because the poster told me that a 220uf cap in a tube amp is a "huge" value, which it certainly is not. Fender uses that value all the time, in several tube amps.

The capacitor on a tube rectifier does not cause the rectifier to draw too much current, unless the capacitor is defective. It's the LOAD- not the capacitor- that draws the current from the rectifier tube.
And so if I want 220uf X2 in series, bypassed by 220K X2 there is absolutely no problem for a rectifier tube. And if I want 470uf, 1000uf, and up, that's no problem either.

And so exceeding 60uf for a rectifier tube filter, does not "shorten" the life of the tube. That's ridiculous. BUT low heater voltage WILL shorten the life. As long as the LOAD (not the cap) does not exceed the output rating of the rectifier tube, there is absolutely no problem. Just lower ripple.

And if I prefer to use a bigger cap (or a much larger cap) to reduce ripple voltage, (or reduce it to hi fi specifications), there is nothing improper at all about that either.

[tedmich]

doesn't the Mesa Dual Rectifier use 110uF at the first PS node (series 220uF/150k eq. resistors) and the reason its a "Dual" is cause they didn't want more than ~55uF per 5AU?

[Gtr_tech]

It has everything to do with it, because the poster just told me that there was no such thing as a 10,000uf cap in a tube amp, that's wrong.
And if HiFi solid state amp can have 10-20Kuf caps in power supply (which they do frequently) I can have the same in my tube amps, no difference.

>>And that is absolutely pointless....and apples and oranges. Again...we weren't originally talking about DC heater circuits. We were "discussing" plate supplies.....which was what the OP asked about. So quit twisting and bending the subject to suit yer needs.

This began because the poster told me that a 220uf cap in a tube amp is a "huge" value, which it certainly is not. Fender uses that value all the time, in several tube amps.

>>Unless its an SVT or similar....it *is* a huge value. A Twin or superlead won't come close to needing that much current reserve. 100u is plenty. But then, no recto tube either.


The capacitor on a tube rectifier does not cause the rectifier to draw too much current, unless the capacitor is defective. It's the LOAD- not the capacitor- that draws the current from the rectifier tube.
And so if I want 220uf X2 in series, bypassed by 220K X2 there is absolutely no problem for a rectifier tube. And if I want 470uf, 1000uf, and up, that's no problem either.

>>What happens when you throw the stby switch?


And so exceeding 60uf for a rectifier tube filter, does not "shorten" the life of the tube. That's ridiculous. BUT low heater voltage WILL shorten the life. As long as the LOAD (not the cap) does not exceed the output rating of the rectifier tube, there is absolutely no problem. Just lower ripple.

>>History (and my experience) says otherwise. I've had a couple amps thru here that some "guru" had installed oversized filter caps in. The complaint was "it worked great for a while then started blowing fuses". Wasted recto tubes both of them.

Old USA produced tubes seem to be able to tolerate a *slightly* larger than max spec first filter. New production won't. Their track record is bad enough with "correct" values....

And if I prefer to use a bigger cap (or a much larger cap) to reduce ripple voltage, (or reduce it to hi fi specifications), there is nothing improper at all about that either.

>>Great. You do what you want. I don't want to see a freshly recapped amp come back in a month with a shorted recto tube. Thats just bad business...

[loudthud]

The capacitor on a tube rectifier does not cause the rectifier to draw too much current, unless the capacitor is defective. It's the LOAD- not the capacitor- that draws the current from the rectifier tube.
And so if I want 220uf X2 in series, bypassed by 220K X2 there is absolutely no problem for a rectifier tube. And if I want 470uf, 1000uf, and up, that's no problem either.

And so exceeding 60uf for a rectifier tube filter, does not "shorten" the life of the tube. That's ridiculous. BUT low heater voltage WILL shorten the life. As long as the LOAD (not the cap) does not exceed the output rating of the rectifier tube, there is absolutely no problem. Just lower ripple.

Check some of the links on my profile. Download yourself a copy of PSUD2 if you have a PC and play with it a while. You will quickly see that rectifier RMS current increases as you increase the capacitance. Or just insert a current monitoring resistor between the center tap and ground of a full wave CT power supply, measure the current, then increase the capacitance.

[Jazz P Bass]

I don't know if anyone bothered to read the pdf file I posted, but it stated that after a point, a higher capacitance does not do any good.
There are no benefits.
It was also stated that a capacitance filter alone is ideal for a Class A amplifier.
An LCR filter is recommended for Class AB.

[Enzo]

Clearly the "no 10,000uf cap in a tube amp" referred to the filter cap off a tube rectifier. SO the point was - considering the TOPIC at hand - that no TUBE RECTIFIER would have to face a 10,000uf cap. The fact that there could be a 10kuf cap in some other application within a tube amp is irrlelvant.

Guruman is just trying to slide his arguments around to score points.