Thinking About Tubelab Simple PP

[Doc Jr 8156]

Hello,
I am thinking of building a Tubelab PP to complete the line up (2 SSE and 2 TSE). I have a spare power transformer, Hammond 370hx @ 550VCT. I am looking at the version using EL84s. Is my power tranny adequate? Hom many watts is the output of Tubelab PP? OPT will be Electraprints. Thanks. Godspeed.

[rknize]

The 370HX should work fine. Your B+ will probably come in a bit lower than what George suggests, but that will allow you to run the New Sensor EL84 (Russian 6P14P) variants. I can only use JJ tubes in mine. The reduced load might actually result in reasonable operating temps in that Hammond.

Power output will be on the order of 20W for pentode mode, but you'll probably want to run UL. George recommends around 7.6k primary impedance on the OPTs.

[Doc Jr 8156]

Thanks Russ, what is the advantage of ultra linear? How many watts? Thanks. Godspeed.

[akimmet]

In general ultra-linear gives you less distortion, with only a small drop in output power (15-17W). Triode mode has the least distortion, but a large drop in output power (5-8W).

[Doc Jr 8156]

Thanks akimmet. Godspeed.

[rknize]

The merits of UL are often debated. For example, the position of the taps is usually something like 40% even though the most optimized position depends on the output tube and even transformer itself. Mine measures fairly well in pure-pentode mode. Many OPTs come with the taps regardless, so it doesn't hurt to make use of them if they are there.