6V6 how hard can/do we push them?

[Kegger]

I'm wondering others use of the 6V6 an what is the consensus of "pushing" them? (vintage an new)

I know quite a few guitar amps run the voltage up there on them but not sure of there dissipation.

Here is my scenario:

I built a single ended amp, actually my "tube tester amp" running 7AC pinout tubes triode strapped
with a octal socket for driver pinned out to the 8BD (6SN7 type) but I also have an adaptor to run
a 9A pinout (12AT7 type) in that spot to "test" an listen to any of those types for noise or whatnot.
(all pinouts are top side monitorable)

Outputs are cathode biased, running 5V4 rectifier I get roughly 340v B+ which is my center voltage,
going to 5AR4 obviously is higher and the 5Y3 being lower plus the rest that pinout in the same slot.

(For the 6V6)
With the 5V4 I get roughly 320v plate to cathode at 46.8ma, for plate dissipation of just under 15w.

With using 5Y3 I get roughly 289v plate to cathode at 42.6ma, for plate dissipation of just over 12w.
(I think I'm alright with this setup but the other I believe is pushing it..?)

--------------

I am trying to run a "universal" cathode resistor(470 ohm), by changing rectifiers I can get different
voltages and the usual say KT88/6550's draws 60ma each, where your 6L6 plus EL34 draw just over
50ma, with everything between there running just fine, it's the 6V6 that brings up the bottom an by
running them kinda hot makes others fall in line pretty well but how hot to think I can get away with.:scratch2:

 

[willyrover]

In my 6V6 PP I run 374v plate at 34mA, for a plate dissipation of just under 13w per tube.

Rectifier is a 6CA4.

Not pushing them really but near the top of design values...I think.

 

[Kegger]

Triode, Ultra Linear or Pentode mode Will? If Pentode may I get the screen voltage?

I'm going to assume if your cathode biased it's around 17v on those cathodes then?

 

[GordonW]

I've beat the living $#!^ out of 6V6s before... sometimes out of an unrealized error, sometimes on purpose.

When I was building my DuMont chassis-based custom amp, I, for a while, had an error in wiring (not realizing the heater winding was grounded INSIDE the transformer), which resulted in me running the 6V6s at nearly 360V plate, 335V screens, with only a -17v bias (where it SHOULD have been -23V!). Even at THOSE loadings, only a FEW 6V6s would start to red-plate slightly. That was close to FIFTEEN WATTS dissipation PER TUBE. When I fixed the cathode resistor circuit, there was no lingering damage, even to those tubes that had red-plated (they still tested and worked fine)... even after I RAISED the screen voltage to nearly 350V (to get the cathode voltage up closer to -24V, so it would properly run the heaters of the input tubes wired in series)...

They're hardy little beasts, IME. I regularly see them in guitar amps, running at 330V with nearly 40ma per tube... that's like 13 watts. Some even as high as 420v with 30ma per tube! They pretty much don't seem to care.

Realistically, in the real world, they seem to take MUCH more abuse (high voltage/high current simultaneously) than EL84s will tolerate. It's rare to see a completely used-up 6V6, but I regularly see EL84s that have crashed-and-burned...

As for voltage- here's what EH says about their 6V6s:

The all-new 6V6EH combines a specially developed cathode coating, careful alignment of the grids and tri-alloy plate material to create a rugged, wonderful sounding 6V6 that performs flawlessly up to 475 volts. Perfect for high plate voltage amps like the Fender Deluxe Reverb. This tube is perfect for guitar amps - it can take the abuse.

I've seen these running as high as 420V, in person. They just happily keep taking it and dishing it out!

IMHO, they really are 'little 6L6s'... in pretty much every way. Same pretty much in the abuse-tolerance department, within proportion to their smaller size. It's usually output transformers that limit their performance in many amps we see, not the tubes themselves!

Regards,
Gordon.

 

[Kegger]

COOL!
That is what I was hoping to hear from others and what I had expected..:thmbsp:

Here is the excel spreadsheet I'm working on as my "tester" guideline with using
a set standard plate voltage for each tube type then writing down the cathode
voltage on each tube after testing it then matching them up from there.

I'm running this amp/tester off my variac, so I get the exact same plate voltage
on every tube type I test then compare and come up with a "standard" to go by.
(still shooting for always 115-120v AC input so filament voltages are correct)

The plate to cathode voltage along with dissipation an current are formated cells
so they calculate once you add in your measured plate and cathode voltages.

This will evolve over time with adding meters, easy to get at connectors, anything
else I think will aid in it being a useful tool.:scratch2:
(I'll attach some pic's of it later)

(using 5Y3GB rectifier)
Today/yesterday was the first real testing of tubes, I've done about 25 6V6 tubes.
(the other tubes are just showing the type of progression I will be following)

 

[Kegger]

Here is a pick of the beast with a pair of 6V6G tubes for the outputs, 12AT7 driver and 5Y3GB rectifier.