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dionisio 23rd March 2005 02:15 AM

Triode strapping 6l6gc PP
2 Attachment(s)
I would like to try strapping my 6l6 PP into triode mode.
I did some searches and I think I found, what I was looking for.
I've attached schem. and am hoping someone could take a look and see if I'm on the right track, or if I've missed anything.

Is it really this simple : remove the +v screen taps and connect the screen to the plate with a 100 ohm res. ?

what wattage for the resistors 1/4 ? 1/2 ?

Thanks for reading :)

SY 23rd March 2005 02:41 AM

Yup, that's it- but do check the max screen/plate voltage ratings for your tubes. I don't remember offhand what they are, but I'm pretty sure they're on the tube datasheet and I'm pretty sure they're less than 483V (warmed up, 440V or thereabouts).

SY 23rd March 2005 02:45 AM

Looking up the GC version, it is rated to 450V in triode. So you're good to go.

ray_moth 23rd March 2005 02:52 AM

Yes, basically you can do that, although I suspect the 6L6GC in triode mode might be happier (i.e. give lower distortion) with a somewhat higher impedance load than it needs in UL mode. With only 100 ohms in each screen circuit, you could use 1/2 watt resistors (theoretically, you don't even need 1/8 watt, but the tube pins can get hot). Make sure each resistor is soldered very close to the screen pin, so it's effective in preventing parasitic oscillations.

Tom Bavis 24th March 2005 12:47 AM

Since the screen voltage is going up, the idle current will go up a bit. I would be safest to increase the cathode resistor.

dionisio 24th March 2005 01:34 AM

Definately a step in the right direction!!!!

I like the sound much better, although there is a caveat. Before I strapped the output tubes I had been noticing a small amount of distortion (sounded like clipping) while playing anything with very heavy low frequencies or loud quick high freq. In triode mode this is far more pronounced along with some hum, but I've also realized it's only on the left channel. ( a nice clue) Previously I thought the power supply was at fault. So I've got some digging to do.

To despite this it sounds quite good at low volume and I've gotten a glimpse into the joy of making better music!

SY, Ray moth, Tom, Thank You , for your replies they are greatly appreciated!

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