Filter cap size question. Fender blackface.

[frus]

I apologize in advance for hijacking the thread

I've recapped a blackface super reverb the other day. I used these caps:


F+T 80uF, 450V :: FT Standard Caps :: F+T Capacitors :: Electrolytics :: Capacitors :: Passive Components :: Electronic Parts :: Banzai Music GmbH

I replaced the original 70uF 350V ones

When I play it really loud (in overdrive), I can hear (and see on the scope) 100Hz signal modulating the sound. I know this is how these amps work, but it sounds worse than usual.
How can I check if the new caps are alright or not?
It seems that the other nodes (screens and preamp) are OK, since I can't see any signal modulating these

Thanks!

[Leo_Gnardo]

frus, that's what they do. You can increase the main filter just a little bit say to 100 uF caps but you're up against the limit of what tube rectifiers can drive.

If you go to solid state rectifier, you could put in bigger filters say 220 uF series pair for 110 uF total main filter. OTOH the higher voltage you derive leads to a cleaner brighter tone which may or may not be where you want to go with your super reverb.

One thing I do, go to 47 uF on the second stage filter. It doesn't "fix everything like magic", hardly, but does help smooth out the screen grid DC plus all the lower-voltage nodes.

[Tom Phillips]

I apologize in advance for hijacking the thread...

Well...If you realize you are hijacking then just start a new thread & make it your own in situations like this. Easier than apologizing.

[frus]

well it did contain a recommendation for filter caps, I just felt a connection with this thread

Leo, thanks for the suggestion, I'll try that

[mhuss]

Almost all 'classic' tube amp supplies show waveform ripple on the main B+; fortunately, the push-pull output stage cancels it out. As long as the screens and further downstream are clean, no worries.

[frus]

Normally yes, but when you turn it up (especially if you're already in overdrive), only one tube is actually conducting at the same time, so you also get the ripple amplified. As you turn it up more, you tax the power supply more, so it gets worse (I GUESS that's what happens)

here's the simulation



You can clearly see it on the scope too (I don't have the photo)

And you CAN hear it, I've got some kind of recording (not very good though)
It's the amp on 10, plus tubescreamer for some more sustain
If someone with more experience with these amps could chime in if this is too much or normal, I would appreciate it

https://soundcloud.com/frus-2/broom