Amp using 6550 tubes- output tranny?

[Bob M.]

I'm building myself a new amp. I'd like to try 2x 6550 power tubes in it as I like clean with a big bass sound. I'll be using one 12" speaker and the amp is intended for electric guitar. The B+ voltage will be about 450 Vdc.

I'm to the point of choosing an output transformer and I've been partial to Hammond transformers in the past. I really want to 'try' 6550 tubes but I 'may' end up using 6L6s or a variant like the 7581A. I want to choose an output transformer that would work well with either 6550 tubes or 6L6 tubes, just so I'm covered. Is there such transformer? I'm not so good with the impedance numbers. Any transformer recommendations or reference to reading material would be of great help.

Thanks,

Bob M.

[Mouthurst]

I beleive It depends on how much power you want-the hammond site has lots of info and even give the suggessted tubes.

Awhile ago I used one from an old 55 watt PA head which used el34s for a 6550 amp, I think it was 1V in 55watts out or 5500k?? Oh well.


Heres the hammond link. You want to look at the "classic" series.

http://www.hammondmfg.com/claspg.htm

[J Martin]

The Hammond 1650N would be a good choice for either type of tube. I have built with it several times with 6L6, 6550 and 4x 6BQ5.

jm

[Bob M.]

Hammond transformer choices

Do you think the 1650N (4,300 ct) would be a better choice than the 1650K (3,400 ct)? I'll be running either 2x 6550 or 2x 6L6 into 8 ohms (12" speaker). Both of these transformers are rated at 318 ma, according to the Hammond site.

Thanks,

Bob M.

[J Martin]

Normally the 1650N would be a better choice, but it depends on the design of the power amp. You can get 100 watts out of a pair of 6550s with the Hammond 1650R and the right circuit. The 1650K might be better for EL34 tubes.

Several years ago I bought Kevin O'Connor's book PRINCIPLES OF POWER. It has all the formulas laid out for power amp design including single ended designs. It will save you a lot of time.

[Bob M.]

I think that's the only KO'C book I don't have. I've got most of the TUT books.

Bob M.