Anyone have curves for a 6CD6 in triode? Any idea what the Rp would be at say B+ 160V with say 30ma idle?
Here are some triode curves for the 6EX6, which was a lightly upgraded 6CD6 (ratings). Should be nearly the same curves. (6CD6 Mu 3.9 at 75 mA, 6EX6 Mu 4.2 at 67 mA)
50mA/div Vert., 50 V/div Horiz., -6V grid steps
50mA/div Vert., 50 V/div Horiz., -6V grid steps
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Thanks. I'm thinking of building an amp with these tubes but using those VPT series PTs I'm always raving about. I'm hoping to use a B+ of about 160V and fixed bias or one of Pavel's audipamp.eu solutions. I'm hoping to run a pair with about 1k2 Raa. The actual goal is 1W class A and the rest B.
That would be 300 Ohms per tube in class B and 600 Ohms per tube in class A.
Seems rather low for an 800 Ohm Ri triode.
7867 appears to be a similar tube to 6CD6/6EX6 too.
6KV6 (22 Watt) also similar tube. (6KV6 = 6KM6 with added grid 1 cooler fin)
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Rp is more like 425r at the zero bias line, where it will clip.
Still agree that 300r load on a 425r tube is "bad engineering". Bigger fatter tubes, or wound-up transformers, are not that expensive.
But clearly he is not aiming at a dam-buster. More like an odd-parts project.
Yeah, it "works". You can even make the 28V drive with a triode on the same power supply. Looks like 8 Watts max output. May have to nudge the 15W Pdiss to make a Whole Watt still in A. (Notice >30W of big heaters!! A 6V6 at ~300V can make more audio out than its heater demands.) (Note that running Pentode at ~200V with same load offers ~~30W output.)
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Good to know. Right now I'm running 6N13S PP both halves in parallel into ~600Raa and I like it. I'm not opposed to running pentode mode though. Looks like 2k4 would be better unless I want to parallel tubes. When you say "bigger, fatter tubes" do you suggest something like a (3)6LW6? Also I assume that 30W pentode mode figure is at ~1k2 Raa?
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With -two- of those 1K2 OTs, you could build that Mangini or Crowhurst type amplifier. One for the cathode windings, the other for the plate windings.
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