OT Primary Question

[johnnyreece]

I've got an amp that I've recently finished building, and I think my last question is OT primaries. It's cathode biased and has multiple B+ settings. My plate voltage is between 350-400, depending on rectifier, PT secondary settings, and power tubes. The OT is a 3400 primary with 2,4,8,16 secondary (for a JTM45). I'm thinking these are my likely OT settings:

EL34 and 6L6 - 3400 primary with 2,4,8,16 secondaries
6V6 and KT66 - 6800 primary with 4,8,16,32 secondaries
6K6 - 13600 primary with 8,16,32,64 secondaries

Does this seem reasonable? I can't find data on the 6K6 tubes at high enough voltage. The data sheet shows a 12k primary load for a plate voltage of 285. Obviously, I'll have limited options with the 6K6 tubes, but I think an 8 and 16 ohm option is plenty. I know some people have been successful directly subbing them in for 6V6 with no changes, but I don't feel like living that dangerously. I appreciate any input I can get! Hoping to start carving faceplates soon...

[sluckey]

I would be very nervous running a 6K6 with 350-400V on the plate.

[johnnyreece]

I’m only running those at 350. That’s with a 5Y3 and the lower B+ option. I’m a bit hesitant, but some folks swear they’ve put them in a stock 5E3 with no longevity issues, which is much rougher than I’ll be treating them.

[Stevem]

I don’t understand chancing running the 6K6 outputs.

The difference in the output wattage between these and a 6v6 with cathode bias and in push pull will not change the SPL of the amp by much if that’s your main goal.

[johnnyreece]

Well, in testing, I was able to crank the 6K6 at full volume through a 4x12 and not be uncomfortable. The lower wattage could also allow me to use this with a much lower rated speaker. And, unlike the 6V6, 6K6 is a true pentode. Just another different flavor. As an added bonus, 6K6 tubes can be had for much cheaper. It seemed like a fun exercise. I was hoping for some input about the impedance choice, but no luck yet. I’ve drawn out the load lines, and to me, it looks like it should work. I suppose I shouldn’t expect to be spoonfed everything, so, as I said elsewhere, I guess I’ll just have to try it ‘til I fry it. I have plenty of these tubes to experiment with.

[bepone]

PP or SE?

[johnnyreece]

PP.

[bepone]

it is ok.. also there is wide range of usable impedances for all the tubes.. nothing to worry about..in datasheets yu can find distortion vs load impedance , this is changing, also little bit he character.. but is it ok