Replacing 6L6 with 6V6?

[profgalen]

I have a mid 90s Marshall JTM 30 that has two Sovtek 6L6s. The new JJ 6L6s I bought are longer and won't fit with the cage. They stick out to far even without the cage. New Sovteks seem to be the same size as the JJs. My question is can I use 6V6s if I bias for them?
Is there any thing else I need to do? How much power reduction can I expect?

[Jazz P Bass]

Here is a quote from Kevin O Conner:
"6V6s in 6L6 amps:
1) If B+ is less than or equal to 450V; okay
2) If B+ > 450V; NOT okay
UNLESS– screen voltage can be reduced to below 400V; preferably
below 350V"

And you will have to at least, check how the 6V6's are biased.

[Justin Thomas]

If the JJ specs 500/450 for Plate/Screen respectively compared to 6V6GTA, why not? As long as the 14W plate dissipation isn't exceeded... B+ (schematic) was 459V. Could he just bias them conservatively? I definitely wouldn't use any NOS 6V6s in it. And, JJs are cheap enough... Also, JJ is 3.25" seated. Power reduction? Roughly half, so probably not too noticeable. Feel will probably change, though... HTH,

Justin

[jbltwin1]

AND speaker load will have to change.

[frus]

how about (tung sol) 5881? they are short enough

[km6xz]

Or better $5 for the more reliable 6П3с-е which re-banders labeling as 5881 and selling for 3 times that. It will handle any anode or screen voltage that any 6L6 could survive, and fit. Even cheaper are the 6П3с which are like a super 6V6, same size as the 5881 but a little lower plate dissipation.

[Leo_Gnardo]

profgalen, I hope you're paying attention. Stan km6xz has the best idea yet. The ORIGINAL tubes are still available, may be identified in USA as "wafer-base" Sovtek 5881, imported and sold by New Sensor BUT lots of other vendors have them, some even cheaper than New Sensor. Good tough tubes they are too.

Marshall started using cheap plentiful 6Pi3C-e aka 5881-waferbase mid 90's after supplies of reliable EL34 dried up. After better quality EL34 became available again, Marshall went back to EL34. In the meantime, Marshall designed their amp geometry so that a tube longer than a wafer base 5881 wouldn't fit. Pure genius!