5F6-A Bassman Filter Caps

[drfunkphd]

Hey all,

Just wondering if anyone on here has found any magic formulas for upgrading the filter cap section in a 5F6-A Bassman circuit? I know that there is a lot of talk of doing a totem pole style filter section instead of the spec 20uf caps, but would like to avoid deviating from the magic tweed Bassman formula too much.

If anyone has found anything interesting by experimentation, let me know.

Thanks

[Diablo]

If you don't deviate, how can it be different or improved? I did the totem pole on the first filter to raise the cap voltage rating. Sounds good too with two 100mfd / 450V caps in series.

[stokes]

Are you talking about an original Bassman or the re-issue?The first stage is actually 40uf,two 20uf's in parallel.What exactly do you mean by "upgrade".The only reason for using totem poled caps is to up the voltage value.Just use 2X80uf's totem poled and you will keep the original 40uf value.I would also suggest using Sprague or F&T brand,not any of the Asian Xicons or the like.If you cant find 80uf 2X 100uf will be close enough.

[drfunkphd]

If it ain't broke, don't fix it is my theory with great designs...but I know that this amp was born to be dimed. I just was wondering what others have tried without getting too far from the orignal recipe.

Thanks for your input.

[drfunkphd]

The original. The re-issue is Bassman in name only IMHO.

I only use Sprague or F+T, anyway...until I find something better.

The 80-100 uf in totem pole configuration is pretty much what I figured most would say, but thought someone may have tried something else that may be of interest.

[MWJB]

You can use 2x220uf in a totem pole, the amp may hold together better at very high volume, but the totem pole route is the one most typically used by respected builders. If you havea lot of B+ you might also want to do the same at the screen supply with either 2x47uf (23.5uf total) or 2x80-100uf caps (40-50uf total). You can usually find reasonably sized 450v caps that fit happily in the space of one 500v Sprague atom.

[stokes]

I like to use the 220uf's for some extra filtering,but if you want to keep that tweed breakup,you cant use the over filtering,it'll tighten things up too much.

[MWJB]

Going to 100uf at the first filter won't stop the amp sounding like a tweed, if you regularly play with the amp driven then it might be a good idea, but if not 50uf should be fine. I prefer to keep the power supply well filtered, then if you want a little more 'give' you can always play with rectifiers, or power tubes that compress a little earlier.

[Albert Kreuzer]

GZ34 / 5AR4 maximum capacitance rating is 50µF (2 x 100 in totem pole) for the first filter cap. I wouldn't go beyond that. If you really want to go higher, you can always use a copper cap or a couple of 1N4007s. After the choke you can filter as much as you want.

[MWJB]

A GZ34 will take 100uf happily, as will 5Y3, 5V4, 5U4, yes a copper cap is an option but not a necessity (I have not found them to be any more reliable than a typical tube rectifier).

Popular amps that respect the tube data sheet ratings are few & far between.

[stokes]

Pay no attention to the capacitance ratings in manuals for tube rectifiers.I have a 5R4 with a 220uf on it in one of my builds and its been going strong for about 3 years.The manual says 40uf max,I've even seen a manual that says 20uf max for that tube.I've done other experiments and you can go way over the "design max" with no problems.

[Albert Kreuzer]

Well, I didn't say that you can't get away with it. You could be lucky.
I just said that I wouldn't do it.

[stokes]

Luck has nothing to do with it.The manuals ratings are just too conservative.Just about any guitar tube amp proves that in so many ways.