Capacitor Substitution Sanity Check

[cgiesel1]

Morning all,

I am getting ready to replace the electrolytic capacitors in my old tube amp.
I know it is ok to substitute for the nearest values --uf/v-- but is there a rule of thumb regarding how different the values can be?  What is too different?

The substitutions in question are:

Power supply filter capacitor:

Original equipment:
Multisection
Sprague 270021-56                Substitution with capacitor pack
40uf 450v                             JJ  47uf  500v
30uf 450v                            F&T 30uf 500v
10uf 450v                            F&T 16uf 475v
20uf 25v                         Sprague Atom Aluminum 25uf 25v

The biggest issue I have is the speaker crossover. Can I sub the 16uf 25v caps for 25uf 25v or would that go badly?  I am thinking a close match is a bit more critical in this case? Would I need to change out the resistors?

Speaker crossover:
Original                    Substitute with this?
16uf 25v                  25uf 25v?
the crossover circuit looks like this:  (r2 and r3 go to one terminal, transformer goes to a separate terminal)

                                                               [ R2 33ohm@20%                              |--> OUT
IN? -->[R1 10ohm@20%]-->[cap 16uf/25v]-->| R3 2.2 P 3v                                    |                                                                                                      [ Transformer pri 6000ohm sec 4-6 ohm ]--> OUT

Any advice would be appreciated

[John]

All that should be fine. You might notice a difference with the crossover cap though, I'm not sure. Somebody will be along shortly that knows for sure.

[PRR]

The power DC filter caps are polarized, fine.

Speaker crossover caps *must* be bipolar/nonpolar (or not electrolytic, but in these values a fine film cap would be huge and costly(*)).

Look to DIY speaker stores for crossover caps.

25V on a LOUDspeaker crossover cap is pretty cheezy. OK for a 90-day warranty, but if you like the amp more than 90 months you oughta replace with >50V caps.

Try to stay within ~~20% of nominal crossover cap value. For "16u", aim at 13uFd-19uFd. In today's value-series, 15u is the new 16u.

PartsExpress has been around for decades:
http://www.parts-express.com/
http://www.parts-express.com/cat/non-polarized-electrolytic-capacitors/293

(*) Actually, PE's price for 15u of fancy-film cap is not horrible, and it will last forever.
Metalized Polypropylene Capacitors

[cgiesel1]

Thanks for the reply.  Parts express is one of my favorite sites.  Good call on the non-polarized crossover cap.  A closer examination of the cap showed that it is indeed non polarized.