5k OPT in 45 stereomour?

[Jim R.]

I'm guessing this is ok, maybe with some minor changes to the cathode resistor and/or PS resistor, and PF cap, just want some confirmation and advice.

Thanks,

Jim

[Paul Joppa]

Yes. it's OK.

We use a 3.3uF in Stereomour because it's close enough to both nominal targets of 2.5uF for 2A3, 5uF for 45s. But with a 5K transformer the nominal target is 3.2uF. You could increase the cathode resistor slightly (up to 12%), but I wouldn't. It won't give you any more power, just slightly less dissipation and slightly more distortion. I doubt you'll ever notice either difference.

[Jim R.]

Thanks, Paul. I was considering a slightly smaller PF cap because of the full nickel stack, but maybe the power handling even with the nickel lams is fine, and 40 henries seems to be a sweet spot in terms of choke plates -- meaning enough to keep most opts from saturating.

On with this project!

-- Jim