200W Steel String Singer Build--What PT?

[Drumslinger]

so this amp will be used for small club gigs?

[Cliff Schecht]

Just saw this thread again during a search for "voltage regulation". Update is I dropped it down to 150W and bought a Hammond 278CX for the PT. OT is a now NOS Bassman 100 I also got from dreric. Now I just have to figure out what are the best four power tubes to match that OT, Zpri=2,330 ohms, about 500-520 Vp, maybe 490 or so Vs.

Any opinions? I haven't done a good study on the plate curves yet. leaning towards KT88s.

Oh, and I'm saving that big chassis with the 6SL7s for a 300W SSS/Dumbleland using the 300PS OT. Bought an Antek 500-0-500 toroid two secondary windings in parallel and a big steel pot for it too.

Still crazy after all these years!

With the numbers you mentioned I was thinking KT88 too. They love about 500-550V plate voltage and you can play around with the screen voltage to get different sounds. I dropped the screen down to something like 300V (520V B+) on a SE KT88 build and loved the results (high gain amp topology). For a clean amp you'd definitely want a higher screen voltage like you spec'ed. Probably would be a very unique sounding Dumble-style build.

I think 300W is past the current rating of my 60+ year old house wiring..

[Structo]

Nah, that's only 2.5 amps @ 120vac

[David Root]

That's right. It's a mere bagatelle!

[Cliff Schecht]

Nah, that's only 2.5 amps @ 120vac

With heaters and all it's closer to 4A at 120V but still, I bet my house lights would dim badly when I kicked that amp just into standby .

[Structo]

Heheheh, yeah my lights flicker just a touch when I flip on my 100.

[tictac]

I built a stereo guitar amp with 2 x 6550 per side using a One Electron BFT-1 power transformer. It's nice because the secondary has two B+ windings, two 6.3V windings and a 5V winding.

I'm getting 530V on the high winding for the plates and 360V on the low B+ winding which I'm using for the screens and standby. Lots of current capacity too.

TT

[David Root]

tictac that is a great PT, I have two of them, one in my 6SL7/8417 ODS and the other one unmolested, as yet, (heh heh!).

I love the designer's sense of humor too! (BFT-1). 16 lbs and Fat Stack, huge PT.