PS evaluation

[HeadSh0T]

Hi all

I'm working on a new 300B SET amp and I'm trying to figure out a good powersupply.

I'm using PSU Designer and I came up with the one below..

I'm getting 5mV ripple p-p but I'm a little concerned about that 100U cap after the GZ34.. Is that a problem even if there's a resistor in series before the cap?

Do I need to bypass these caps with a smaller film (like a 10uF pp)??

Thanks

mo

[fdegrove]

Hi,

I'm getting 5mV ripple p-p but I'm a little concerned about that 100U cap after the GZ34.. Is that a problem even if there's a resistor in series before the cap?

No, not at all.

Do I need to bypass these caps with a smaller film (like a 10uF pp)??

The one in front of the choke can be a garden variety electrolytic, the ones behind should ideally be filmcaps which you can bypass if you must.
If you do so use just decreasingly smaller values of the same technology.

Cheers and happy building,

[Saurav]

Are there any reasonably priced 100uF film caps? If there are, I should replace my last PS cap as well as my cathode bypass caps. I guess I should rephrase my question to "what's a reasonably priced alternative to electrolytes in these high values?"

[Brett]

Originally posted by Saurav
Are there any reasonably priced 100uF film caps? If there are, I should replace my last PS cap as well as my cathode bypass caps. I guess I should rephrase my question to "what's a reasonably priced alternative to electrolytes in these high values?"

ASC PP in oil

[fdegrove]

Hi,

ASC PP in oil

Bingo...

Grataku, I sure hope you read this....

Other fine ones are the Ansar MKP caps and the Siemens/EPCOS MKVs.

For info: ASC is the American Shizuki Corp which produced the poyprops favoured by Jean Hiraga no less.

Cheers,

[Saurav]

OK, next obvious question - places in the US where I can buy these? I found some at Angela.com that go up to 50uF, couldn't find a dealer list on the ASC website. And these are a lot bigger than I thought they would be

Related question - how low can I go on the cathode bypass cap for a 2A3? I've seen some 300B circuits with 70uF, but most seem to stick with 100uF. My speakers don't do much below 50Hz, so I could probably get away with a smaller cap here, right? When I get back home I'll pull out my Morgan Jones and figure out how to calculate the impedance at the cathode, but if someone could give me a rough idea of the cap values, that would be a big help.

Thanks,
Saurav

[HeadSh0T]

Thanks for the answers. I was thinking of getting 100uF cerafines. I didn't know 100uF films existed! They must be hard to find.

Are cerafines good for PS?

[grataku]

Originally posted by fdegrove
Hi,



Bingo...

Grataku, I sure hope you read this....

Other fine ones are the Ansar MKP caps and the Siemens/EPCOS MKVs.

For info: ASC is the American Shizuki Corp which produced the poyprops favoured by Jean Hiraga no less.

Cheers,

Thank you, I had already planned on using ASCs for my 300BXLS,
I have been busy with other more important things with regard to my real profession. Actually, there is a very good chance I may have stop this hobby altogether. I would like to finish the few projects I have the parts for, there just is no time for me anymore.

Currently I am trying to figure out what driver stage to use.
Among the candidates are the classic Mu circuit on the triode dick site, Ciuffoli's transformer coupled 5842, the GPimm CCS with the 26, the PMillet 12GN7, then when I was in Italy I bought a copy of "costruireHIFI" (which kicks the Audioxpress's *** from here to eternity) on that I found one of Diego Nardi designs which uses a weird hybrid (bjt/tube) driver circuit and a optical bias.

I hear most of the sound issues of the 300B SE come from inadeguate driver stages.


Saurav,
I think Arrow carries ASCs, it was posted here somewhere.
Moderators should start doing something like creating a parts database and google-ize the search engine...but that would involve more work and less surfing

[Brett]

Originally posted by grataku
the PMillet 12GN7,

These pentodes make really nice drivers

I hear most of the sound issues of the 300B SE come from inadeguate driver stages.

That, the PSU and the 300B not being a particularly good tube.

[grataku]

Brett,
according to Diego Nardi there is no reason for the 300B to sound any different from the 2A3. He claims it's just harder to do right.

Every topology has its merits, for ex. the PSU requirement are relaxed considerably by using GPimm CCSs that now have 4 tera ohm impedance.

Pete really seems to love the 12gn7 have you tried it?