reservoir caps two different size ok?

[mikepukmel]

The original schematic for the Deluxe Reverb AB763 has 2 x 16uf 450v caps, right off the rectifier tube.

I had first bought and installed 2 x 16uf 475v (F&T) caps, but with the standby switch on, measured closer to 490v. I could not find 16uf 500v caps so I used 2 x 22uf 500v.

This had an unexpected effect on the tone of the amp. It removed the 'boomy' low end bass, but changed the tone a little too much. So, I installed a 30uf 500v single cap. The boomy bass is back and its very annoying. Turning the bass knob max or min doesn't change the boomy, loose bass.

Looked for articles explaining the effect of reservoir capacitance on bass response, could not find anything except anecdotal information: "increasing this capacitance tightens up the bass".

So I have a couple of options. I think, based in trial and error, I need to up the capacitance value.

I can get 10uf 500v. But would it cause any problems having

30uf
10uf

in parallel? Do these two capacitors need to be balanced for some reason? E.g. if internal resistance is slightly different, then would that cause one to fail?

Other option, is to go back to 2 x 22uf.

Could also up a bit, 1 x 22uf + 1 x 10uf, but that is the same rated capacitance of what I started with and it had too much loose low end.

[Leo_Gnardo]

Parallel away, it's OK.

[mikepukmel]

Parallel away, it's OK.

Cool, thanks Leo, I'll order a couple more values to mix and match. Geez this amp stuff is fun!

[mikepukmel]

Getting an odd error, when I click the green button:

Error message removed for security reasons -tboy

Hmm, [] operator not supported. That sound serious. I hope I didn't like cause someones tires to go flat or something.

[Leo_Gnardo]

Cool, thanks Leo, I'll order a couple more values to mix and match. Geez this amp stuff is fun!

Do keep in mind, there's such a thing as too much capacitance, which will make trouble for your tube rectifier. So far you're not into that zone. 50 - 60 uF, I wouldn't go beyond there but it looks like you're going to find your happy spot with well less than that.

[Enzo]

Also, measure your caps. Just because they say 16 uf or 22 uf on them doesn;t mean that is what they actually are.

[mozz]

Tweed deluxe? If it uses 0.1uf coupling caps, changing them to 0.047 or 0.022 is a common fix.

[pdf64]

The original schematic for the Deluxe has 2 x 16uf 450v caps, right off the rectifier tube...

While you still can, it may be a good idea to edit post #1 to specify what exactly your amp is, eg copy of BF DR.
Everyone currently reading your threads knows what projects you've got on, but we ought to think about what subsequent searches may turn up.

Consider the possibility that one or more of your caps has excessive ESR, and so isn't actually doing much.

[nevetslab]

Getting an odd error, when I click the green button:

Error message removed for security reasons -tboy

Hmm, [] operator not supported.

Pressing the GRN Thumbs Up button, Fatal User Error: I noticed that for the first time last night

[Chuck H]

Fatal User Error:..

That sounds pretty bad! What with being a user and all. I prefer to avoid fatality.

[mikepukmel]

Do keep in mind, there's such a thing as too much capacitance, which will make trouble for your tube rectifier. So far you're not into that zone. 50 - 60 uF, I wouldn't go beyond there but it looks like you're going to find your happy spot with well less than that.

Thanks Leo, yes, goal is to keep it low 40's or below that.

[mikepukmel]

While you still can, it may be a good idea to edit post #1 to specify what exactly your amp is, eg copy of BF DR.
Everyone currently reading your threads knows what projects you've got on, but we ought to think about what subsequent searches may turn up.

Consider the possibility that one or more of your caps has excessive ESR, and so isn't actually doing much.

Done, thanks. (No ESR meter, yet, Working on it)

[mikepukmel]

Also, measure your caps. Just because they say 16 uf or 22 uf on them doesn't mean that is what they actually are.

Thanks Enzo. That's one tool Id like to get, a capacitance meter. I couldn't afford 500 bucks, is there anything you'd recommend lower than that? maybe used? There are a whole bunch on Ebay around 25.00, didn't think they were any good.

[Chuck H]

I use my Fluke 87. It measures up to 4.7uf. So I test a 4.7 uf cap for a starting reference and then use that cap in series with larger value caps, then do the conversion math. Maybe not super accurate, but certainly accurate to within a uf and that's surely close enough for what we do.

But then again, caps under high voltage squeeze up physically and change value, right?

[Enzo]

My point was that when you are getting down to the difference between two caps close to each others tolerance bands in terms of tone, then you ought to at least measure the caps. Normally I wouldn't bother. When Fender made the Deluxe, a 16uf cap could easily measure 22uf anyway.

Modern meters often include a cap range these days. It measures at very low voltage and so isn't the end-all reading for a 500v cap, but hey...

I know I said measure, but to me it is far more important to check for leakage. There are a bunch of old cap testers that can be found on ebay and elsewhere for $50 or less. I sold my old Eico 950B for $40. It was one of my all time favorite pieces of gear. Here is a story about a bunch of them, note they are all pretty much equivalent. I tended to prefer Eico, but nothing at all wrong with Heathkit. They can test leakage at several hundred volts, just what I need.

https://people.ohio.edu/postr/bapix/CapChkr2.htm