Hoffman 5F6A Tweed Bassman Filter Caps

[dixiepig]

While looking over the schematic I wondered, would it be possible to use a 40uf filter cap at the first stage instead of the to 20 uf caps in parallel? I am sure there must be a reason for using two 20's-just curious.

[stratele52]

I look at the Fender bassman 5F6A , I see the two 20 MFD in parallele. IMO a 40 MFd will do the same job.
The use of 20 MFD could be a "standard" for Fender, they have to stock only one value AND I read that high value cap where very expensive those olds days.

I don't know if somebody have another explanation ?

[phsyconoodler]

You can,but notice they use 600v caps,you cannot use lower voltage ratings.
  In my experience it's best to use the blackface series caps in this location so the caps in standby can handle the higher voltage.

[EL34]

500v caps are fine unless you have some weird transformer that delivers over 500vdc when the amp is on and working normally..
When you put an amp on standby and remove the load, the B+ will go way up.
You have to take that voltage rise into consideration unless you do a simple mod.
I like to have my caps on the cold side of the standby switch to keep them from swelling way up beyond their normal working voltage.

I stock 20/500v and 40/500v
http://www.hoffmanamps.com/MyStore/catalog/parts4.htm

If you must have Sprague Atoms, 1 x 40uf/500v cap is way cheaper than 2 x 20uf/500v caps.

Spragues are getting way out of hand on the prices.
Every time I have to buy them the price has gone up again.

I never thought of it but 1 x 40uf at 500v is a great idea if you have room for it.

Illinios 22/500v are still the best deal

[dixiepig]

Thanks folks I appreciate the quick response!

[stratele52]

I read that Illinois cap are not good, never use it if you want to keep your amp with the best tone. (In the Gerarl Weber book ). You can buy F & T caps.

[tubenit]

I read that Illinois cap are not good,

Just because it is in print doesn't make it so. What is your personal experience with them?

I've never had an issue with them at all.

With respect, Tubenit

[bluesbear]

I've learned an immense amount of knowledge from Gerald's books but, like most humans, he has some strange ideas. I've never been able to hear the slightest bit of difference between the electrolytic brands. Either they work or not.
What is everyone using for the 2 - 70mf 350v caps in the AB763 Bandmaster?
Thanks,
Dave

[John]

Kevin O'Connor doesn't like Illinois either. I bought 'em anyway.

[EL34]

There's already a long thread about Illinois caps
No need to start that subject all over again.

here it is
http://www.el34world.com/Forum/index.php?topic=6320.0

[dixiepig]

So a multi-section capacitor, 40x20x20x20 500v, would work here provided the power transformer was essentially standard for the design.

[bluesbear]

I use the JJ 40-20-20-20. The only one that ever failed was taken out by a shorted 5AR4. There's also an AES brand 40-20-20-20 made in USA. It costs double the JJ and since I've never had any trouble with the JJ's, I see no reason to change.
Dave

[tubeswell]

Doesn't matter what brand of filter cap you use really, as long as the voltage rating is about 20% above what the B+ sees (and as the others said, watch out for the start-up voltage/surge)