Question about power supply filtering

[MikeH]

I’m making a small single-12ax7 preamp using a transformer from tubedepot meant for this purpose. The power supply they suggest is filtered using 2 33uf caps with a 10k dropping resistor in between. Unfortunately I don’t have any 33uf caps on hand but I have several 22uf caps. Would 3 22uf caps with 2 4k7 (or maybe a 4k7 and a 5k1, etc) dropping resistors yield roughly the same result? I know that caps in parallel add up, so at first glance it looks like both scenarios would have 66uf of capacitance but I’m not sure how/if the dropping resistors effect that. Although I’m pretty confident the B+ would be about the same.

Thanks in advance!

[Enzo]

Repeat after me: it is just a guitar amp.

meaning there is nothing precision here. A few volts either way won't matter. 22uf caps should work just fine instead of 33uf. yes, making a three stage filter would work, but seems like overkill to me. Or even instead of two 33uf, use three 22uf, but just double the first one. In other words the original two stage bit with a 44uf and a 22uf stages.

[MikeH]

“It’s just a guitar amp”

[MikeH]

Seriously though- I was pretty sure that subbing in 22uf instead of 33uf would probably yield almost identical results (especially in something as basic as this thing) but I guess I was just trying to learn if those two scenarios are basically identical in terms of filtering capacity or if they would behave any differently. In this instance it won’t matter but someday maybe I’ll be digging into something where it would matter?

Thanks as always, Enzo!

[g1]

Regardless of the caps you use, the current through that series dropping resistor is the same. So if you play with it's value, you are going to alter the voltage drop across it and change your supply node voltages. Sometimes you may want to do that, but I don't think that is what you are trying to achieve here.
So in this case, I don't think you would want to change that resistor value.

[Enzo]

I THINK what he proposed was to change the two stage filter with 10k between to a three stage filter with 4.7k between each. He thus has more or less the 10k total series resistance. I think it unnecessary, but that would seem to be the theory.