chillysalsa said:
Plate resistance, essentially. You can guess 150mA power supply is noted on the schem, so 10mA per is about right. Which I think was already mentioned in this thread.
I probably went with approx. stock operating points, though with higher screen (above limits as PRR noted; not far, according to the screen derating curve which is down all of like...10% at 200V) to pull more current and make it more convienient (running plate and screen from the same supply).
If it weren't for plate dissipation, you could pull probably 40mA or more from each tube at that voltage. As I recall it's pretty good on perveance.
At a lower voltage, say 100 to 150V, you could push more current and just one or two 6DK6s would suffice for each channel of your 300 ohm headphones for ear-splitting levels (100mW into 300 ohms is all of a whopping 30mA bias in class A, and you'll only need 20mW max).
Tim
Sorry... that's what I assumed.
As you can see, I am new to tubes, and plan to build something simpler, or, at least PROVEN first, like this 6AS7 project. http://hem.passagen.se/ebcpecz/Tube/6AS7%20Headphone/headphone.html
I have built 4 or 5 solid state amps already though, like the Dynahi, but tubes are new. Will learn more theory before I begin building, but within the year you may see this 6DK6 design on my test bench.
I wouldn't mind the 15 tube arrangement for more current into 32 ohm headphones. I think Grados shine best when they gave high current, overkill is worthwhile as I have learned with the other amps!
As you can see, I am new to tubes, and plan to build something simpler, or, at least PROVEN first, like this 6AS7 project. http://hem.passagen.se/ebcpecz/Tube/6AS7%20Headphone/headphone.html
I have built 4 or 5 solid state amps already though, like the Dynahi, but tubes are new. Will learn more theory before I begin building, but within the year you may see this 6DK6 design on my test bench.
I wouldn't mind the 15 tube arrangement for more current into 32 ohm headphones. I think Grados shine best when they gave high current, overkill is worthwhile as I have learned with the other amps!
Well yeah, but the tubes kinda tend to implode if you say more than seven words at a time
Not really, though you do need forced air cooling. The spec sheet ratings for the 6KD6 are very conservative since this was intended for use as a color TV horizontal deflection power amp. I've seen a couple of designs. One was an 800W(PEP) design that used four parallel 6KD6's as a class A(2) linear. All suppressors were connected to ground, the screen and control grids connected in parallel. With some -20V bias, the Q Point was 10mA/6KD6. 30W of drive brought that up to close to 1.0A (total) with a V(PP)= 900V. This amp was designed for the 160, 80, and 40m ham bands.
The second design used the same four 6KD6's in push-pull parallel. V(PP)= 800V; V(sgsg)= 300V. This particular amp was an illegal CB (11m band) amp. 5.0W from a standard CB pushed that to some 750W. I don't recall any mention of implosion in either case. Even if it did compromise lifetime, it still would be considerably cheaper than using the "faddish" 8877.
(Although I guess that the 8877 would make one bad @55555555555555 SET: V(pp)=4.0KV (max); I(p)= 1.0A (max); P(d)= 1500W. You'd have to cage that puppy pretty good since it's an external anode, disk seal type. You'd probably have some 3.0KV on it.)
Not really, though you do need forced air cooling. The spec sheet ratings for the 6KD6 are very conservative since this was intended for use as a color TV horizontal deflection power amp. I've seen a couple of designs. One was an 800W(PEP) design that used four parallel 6KD6's as a class A(2) linear. All suppressors were connected to ground, the screen and control grids connected in parallel. With some -20V bias, the Q Point was 10mA/6KD6. 30W of drive brought that up to close to 1.0A (total) with a V(PP)= 900V. This amp was designed for the 160, 80, and 40m ham bands.
The second design used the same four 6KD6's in push-pull parallel. V(PP)= 800V; V(sgsg)= 300V. This particular amp was an illegal CB (11m band) amp. 5.0W from a standard CB pushed that to some 750W. I don't recall any mention of implosion in either case. Even if it did compromise lifetime, it still would be considerably cheaper than using the "faddish" 8877.
(Although I guess that the 8877 would make one bad @55555555555555 SET: V(pp)=4.0KV (max); I(p)= 1.0A (max); P(d)= 1500W. You'd have to cage that puppy pretty good since it's an external anode, disk seal type. You'd probably have some 3.0KV on it.)
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