• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Crosstalk in twintriodes?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
There could in theory be some coupling from cathode to cathode through the heater.

Just tie one side of your heater supply to ground. If you have to float the heater at a high voltage (in a cathode follower) put a cap from the resistor divider to ground.

It's really nothing to worry about. Even in the worst case scenario of inter-element parasitic capacitance you'll probably get more crosstalk from other sources.
 
Crosstalk between triodes

Crosstalk can occur not only by capacitive coupling but by stray electrons from one section getting attracted to the plate of the other section. Most modern dual triodes are designed to close-off any openings in the plates, but some older types, especially 1940s-vintage 6SN7GT and 6SL7GT tubes had pretty large openings that let this thing happen. I once built a two-stage amplifier using a single 6SL7GT and it had a very strange distortion that I tracked down to this type of coupling.

Putting a shield between the sections is the best. The old 6CG7 did this, but it later got replaced by the 6FQ7 which eliminated the shield. Other tubes with built-in shields between the sections include the 6BQ7, 6DJ8, and 6N1P.

- John Atwood
 
I'm using a vintage Tung-Sol 6SU7GTY, wich is a dual triode, in my amp. At first I had your concern but decided to do it anyways. One triode on L channel the other on the R. They are constant current loaded and at full volume swing 260Vp-p. There is absolutely zero crosstalk. First I disconnected the L input and the R speaker. Turned it all the way up, couldn't hear a thing even with my ear to the speaker(Ok, there was a very small hum from the power supply, but it's a SE amp, give me a break!). Then I tried it vice versa, same thing. Then I hooked it to the scope, there were no traces of the other channels signal.

Perhaps it was just this type of tube or the constant current loading. But that's my experience with this matter.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.