EL34s in a 60W Mark Amp

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lions
Mark II
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EL34s in a 60W Mark Amp

Post by lions » Sun Jul 29, 2018 12:31 pm

I've seen boogiebabies say you can run EL34s in a 6L6 amp: http://forum.grailtone.com/viewtopic.php?t=3990
Old Mesa's ran 470 ohm screen grid resistors on the outer EL34 sockets.
If you want to run EL34's then go ahead. You dont need to install a bias pot, you just need to make sure that your tubes are not running hot or too cool. The input impedence on the OT is where you really need to know what type of load the EL34's will be seeing. I have run a lot of EL34's in 6L6 amps, including the SLO 100 with no modifications.
A 1K 5 watt screen resistor would not hurt, but mesa has been running 470 ohm on the simul sockets and 6L6 sockets at 483V+ for years. I would just make sure that your tubes do not draw a lot of bias. A bias meter would help, but it probably running -57 V which would be fine on almost any mid range natural current draw EL 34.
Any more info on this? Would love to try 34s in my 60w. I figured this would require modding though?

gts
Mark IV
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Location: Looking over the shoulder of the guy who lost his apples - not that he really ever had any to lose.

Re: EL34s in a 60W Mark Amp

Post by gts » Sun Jul 29, 2018 1:09 pm

lions wrote: Any more info on this? Would love to try 34s in my 60w. I figured this would require modding though?
If you read the whole thread.... mods are not necessary. (see BB's comment below, BOLD is mine)
Boogiebabies wrote:Old Mesa's ran 470 ohm screen grid resistors on the outer EL34 sockets.
If you want to run EL34's then go ahead. You dont need to install a bias pot, you just need to make sure that your tubes are not running hot or too cool. The input impedence on the OT is where you really need to know what type of load the EL34's will be seeing. I have run a lot of EL34's in 6L6 amps, including the SLO 100 with no modifications.
You even quoted BB. What more info do you need. If he says it's ok, go for it!
Boogiebabies wrote:A 1K 5 watt screen resistor would not hurt, but mesa has been running 470 ohm on the simul sockets and 6L6 sockets at 483V+ for years. I would just make sure that your tubes do not draw a lot of bias. A bias meter would help, but it probably running -57 V which would be fine on almost any mid range natural current draw EL 34.

lions
Mark II
Posts: 75
Joined: Thu Feb 22, 2018 11:37 pm

Re: EL34s in a 60W Mark Amp

Post by lions » Mon Jul 30, 2018 1:34 pm

gts wrote:
lions wrote: Any more info on this? Would love to try 34s in my 60w. I figured this would require modding though?
If you read the whole thread.... mods are not necessary. (see BB's comment below, BOLD is mine)
Boogiebabies wrote:Old Mesa's ran 470 ohm screen grid resistors on the outer EL34 sockets.
If you want to run EL34's then go ahead. You dont need to install a bias pot, you just need to make sure that your tubes are not running hot or too cool. The input impedence on the OT is where you really need to know what type of load the EL34's will be seeing. I have run a lot of EL34's in 6L6 amps, including the SLO 100 with no modifications.
You even quoted BB. What more info do you need. If he says it's ok, go for it!
Boogiebabies wrote:A 1K 5 watt screen resistor would not hurt, but mesa has been running 470 ohm on the simul sockets and 6L6 sockets at 483V+ for years. I would just make sure that your tubes do not draw a lot of bias. A bias meter would help, but it probably running -57 V which would be fine on almost any mid range natural current draw EL 34.
It just seems counter intuitive!

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