Marshall JCM800 copy. Safe conditions for 6L6GC and Lower output power?

[walkman]

Hi I’m having some trouble understanding the safe conditions for running 6L6GCs in a Marshall JCM copy that i’m working on.The OT has is 4ohm /3200 and 8ohm /3800 and screens and plates are both at 460v with bias of -51v.

The Fender super reverb uses 2ohm/ 4000k OT at -52v however an example from the data sheet states 5K6 with 450v on the plate 400v on the screens.

Other places suggest 6600 for 450-460v. So to be conservative i could run 16ohm speaker on the 8ohm tap and a 8ohm speaker on the 4 ohm tap. Looking at the interactive valve data sheet at https://bmamps.com/ivds.html convinces me that this the way to go and that 3200 would require a much higher bias voltage.

How does the super-reverb get away with it?

I was hoping that with 6L6GC that the output could be reduced to closer to 30 watts rather than 50 watts with EL34.
From what I understand 450 /460 is going to be too high for 2x6V6, however the bias is much lower voltage about 35v.

I know by changing tubes it not going to change the whole amp to be a deluxe reverb, that’s not really the point.

I guess it is more realistic that a different power supply (or a completely different amp) wth plate voltage of 360v and cathode bias for either EL34 or 6L6GC would be the best way to get the lower output.

In then end i’m want to get “the best” from what I’ve already got rather that try to style the amp into something it’s not.

Suggestions welcome.

[vampwizzard]

youll have to rewire pin 1. youll have to rebias. Id suggest looking at a peavey XXX and see how theyve done it. Looks like they use a switch and rewire. Kustom Double Cross, Carvin Legacy VL-100, Bugera 6262 also do some form of this. That may help.

edit: If you wanted lower power as well... have you considered 6V6's?

[walkman]

Yes it’s wired correctly to support 6L6GC now. Plate and screens are at 460v with 51v bias.

[shooter]

what power is each tube running?
changing operating characteristics will change the amp "flavor".  The difference in "sound" 30 to 50W isn't BIG until you start hitting 8 on the dial.  spend some time with the master closer to 6 and see what "range" you can get with pickups, pedals and pre-gain, then move to the pa.

you can covert it to self biased and you'll be in the 25 - 30W

[PRR]

Bias voltage has no effect on FULL Power.

Full Power depends on plate voltage, *screen* voltage, and load impedance.

The 6L6GC's tame cathode will not pass as much current as the EL34. Fender's 4K load is about minimum; 3.2K may give the tubes hernias.

Use your 3.8K load, 460V plate is fine, 400V-460V on G2 is fine. Bias for like 20W Pdiss, around 35mA. Go by the mA, set the bias voltage to get that 30mA-36mA zone. I would expect nominal -50V, but +/-20% at least, so you need to be able to dial-down past -60V, should not need to dial-up past -40V.

[pdf64]

...Looking at the interactive valve data sheet at https://bmamps.com/ivds.html ...

That web tool is fantastic, but for its results to be meaningful, the Vdc conditions at full loading (ie fully sagged) should be used; if the idle voltages are used, its results will be inaccurate, much higher dissipations and power outputs than are actually the case.