Big caps in power supply

[Shappers]

Hello all,

While waiting for my Crack to be sent out I have been rummaging in my components box. I have 2 high quality low ESR Rifa 1000uf 450v caps that I would love to put in the power supply. At least one of them anyway.

I have read all the posts but still I'm not sure if it should be the last or the first cap? And if I could use 2 of them, where would the most suitable place for them be?

Space it not a concern as I have a custom box which is a bit more roomy than stock. Once up and running I would also be bypassing the last ps cap to tweak the sound.

Thanks for any advice.

Steve.

 

[Mosez]

Steve,

I asked a similar question a couple of days ago which resulted in an interesting discussing on chokes, power caps and coupling caps and how they all work together. You may want to take a look in that topic while you wait for a specific response.

 

[Shappers]

Thanks for the reply, I think it was mainly that thread which is confusing me.

From that thread, I read that the first cap should be the large one, and that the last cap should be as small as possible, but at least twice the size of the output caps.

But then looking at other peoples builds, I see that they have placed the large cans in the final position.

Steve

 

[davew]

I assume the PSU is currently all stock. I think you'll get best results by installing the larger value cap(s) beginning with the first position, right after the bridge. The stock 220uF cap in the last position already satisfies the ratio to output cap comments. In general, I'd want the most filtering early in the PSU.

 

[Paul Birkeland]

Hmm, two 1000uF caps and one 500 ohm 10W resistor (put the two 270's in series) may be sufficient for the entire B+ supply (IE - no 3rd cap) if indeed these are very low ESR.

If it comes to it, you can just switch back to the 3-cap B+ supply.

 

[Shappers]

Mmm, thanks for the replies guys.

I'm going to investigate the ESR specs of the caps I have vs the stock items. Mine just may be low ESR for their size but then again they are much larger than stock.

I'm going to do a little homework before I decide which way to jump.

Steve

 

[Paul Birkeland]

I'm going to do a little homework before I decide which way to jump.

You can always do a pre build on a piece of wood with octal relay sockets.  A 6SN7 will work well enough to use for evaluation in an octal socket.