# 6V6 in a Metro JTM45 ?



## Louis (Apr 26, 2008)

Hi guys ,...........what would need to be changed if I wanted
to install 6V6's in a JTM 45 Metro amp without changing the tranny?
And if it can be done ,........would I keep the GZ34 rectifier or install a 5Y3 or else ?

Tx


----------



## mhammer (Nov 30, 2007)

6L6s can be simply inserted into the output tube sockets of an otherwise 6V6-based amp. I've done it, and sometimes the results are pleasing.

*BUT* you CANNOT do the inverse (6V6 into normally 6L6 sockets) unless there is something truly unusual and idiosyncratic about the amp. The normal plate voltage on 6L6 tubes is noticeably higher than what a 6V6 can survive. So what you propose is contra-indicated unless you really like shopping for new tubes.

You ask what would need to be changed. I don't know nearly enough about them, but at the very least you would need to reduce the plate voltage. At which point it starts to get more involved, clearly exceeds the sum of both your knowledge and mine, and starts to run into costly fees for someone else to do the requisite mods.


----------



## sammyr (May 7, 2013)

you can run 6v6's but youll need a rectifier swap and some minor changes to the bias scheme. A 5y3 rectifier should drop the voltage enough to be able to run 6v6's without blowing them up. Youll need to to change the bias range resistor from 180k(i believe, stock) to 220k and the bias splitter resistors from 220k to 100k. This should put your bias in the realm of what's needed for a 6v6. Set the bias and you're off to the races.


----------



## Louis (Apr 26, 2008)

Thank's guys !....................Appreciate !
Don't wanna cause any damage thats for sure so better ask first!


----------



## sammyr (May 7, 2013)

heres a schematic for a 6v6 plexi. although it has a solid state rectifier it will show you where to make the modifications. Wayback Machine


----------



## gtrguy (Jul 6, 2006)

The JJ 6V6S (which doesn't sound like a traditional 6V6 to me, more like a 6L6) can handle 450V plate voltage. Keep in mind also that it's less about the plate voltage and more about the dissipation. Bias appropriately and you shouldn't have any issue- Fender ran the 6V6 in blackface Deluxe Reverbs at over 400V on the plates.


----------



## Louis (Apr 26, 2008)

sammyr said:


> heres a schematic for a 6v6 plexi. although it has a solid state rectifier it will show you where to make the modifications. Wayback Machine


Thanks !!


----------



## mhammer (Nov 30, 2007)

gtrguy said:


> The JJ 6V6S (which doesn't sound like a traditional 6V6 to me, more like a 6L6) can handle 450V plate voltage. Keep in mind also that it's less about the plate voltage and more about the dissipation. Bias appropriately and you shouldn't have any issue- Fender ran the 6V6 in blackface Deluxe Reverbs at over 400V on the plates.


Maybe so. I'm just trying to avoid anyone thinking they can yank the 5881s out of an amp that applies near 500V to the plates and stick in any old 6V6.

You know, internet and all.


----------



## gtrguy (Jul 6, 2006)

mhammer said:


> Maybe so. I'm just trying to avoid anyone thinking they can yank the 5881s out of an amp that applies near 500V to the plates and stick in any old 6V6.
> 
> You know, internet and all.


Definitely, always good to be cautious! In this case though as long as the amp is properly biased after the swap taking into account the measured plate voltage it's a pretty safe swap to make. Even the EH 6V6 can handle pretty high plate voltages.

Just putting the 6V6 tubes in without biasing is definitely a potential recipe for disaster.


----------



## nonreverb (Sep 19, 2006)

Probably not a bad idea to determine the output transformer primary impedance as well.


----------



## Lincoln (Jun 2, 2008)

Another blast from the past!!! I have most of a JTM45 kit sitting around gather dust. Don't really want to make another JTM45, since I've got one already. Thinking of using some 6V6's in it along with a suitable OT.


----------

