American Viking

I would stay away from the 6V6 in an amp like that. You're going to get a lot of early power tube breakup and I wouldn't think that would sound good with all that front end gain. I think those KT77's or E34L's would be the better suited tubes for a 900. Hell, for any heavy type of music I love KT88's in everything.
6V6's sound great in those Orange Rocker 30's but those are a more rock type sound and don't have front end gain like a 900 does. Only other thing I can think of right off the top of my head that has 6V6's is some old Fenders.
Experimentation is key to everything though.

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Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

Marshall Amps

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MartyStrat54

I just keep seeing more and more problems with JJ's. Matched sets that are not really matched. Bad tube in a set. It's scary. You buy a matched set and you put the tubes in and the amp goes for weeks running way to hot before you figure out you have an unmatched set of tubes. I mean who is going to reimburse you for amp damage when a JJ power tube goes and the fuse doesn't blow soon enough?

Worse is the posts I read were new JJ's are installed and one red plates right off the bat. "Oh, it's a bad tube, we'll replace it." In the meantime twiddle your thumbs since your amp is down.

Lot's of people love JJ's. Not me. I go with a power tube I can rely on...NOS!

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MARTY

2009 Gibson Explorer-Hell Raising Machine
1989 Fender Strat Plus USA
2008 Fender Tele USA
2004 Schecter Elite w/DiMarzio's

TSL100
TSL122
TSL602 #1
TSL602 #2
DSL401 #1
DSL401 #2

ekkybedmond

Guess it's got a lot to do with the vendor, if he sells tested tubes, or not.

danmahoney

Hi Guys,
I`m actually waiting for the parts right now to mod my 1990 JCM 900
(4101 combo) to run on 6L6s (Tung Sol 6L6 STR`s).
I know most people go in the other direction but I really love the clean sound I get out of the 900 series with the right 6L6s in there.
I`ve got the spec here that covers what Marshall recommends in order to do the mod.
I`m planning on only changing R31-34 from 2K2 to 470 ohms, and R28 from 220k to 47k. Marshall recommends a lot more.
My question is will I potentially be damaging my amp by doing the minimum I`m planning?
I could change the other resistor values while I`ve got the board out but I don`t have the right cap values to start changing those, and I`d prefer not to start messing around with the leads on the power tranny (unless it really should be done in order to keep the amp running safely).
Here`s a link with detail on the mod from Marshall:

http://www.cowboymafia.net/frankie/5...conversion.pdf

Any suggestions and advice would be much appreciated. Thanks.
Dan
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JCM 900 (4502) (Tung Sol 6L6 STRs) (1999)
JCM 900 (4101) (Tung Sol 6L6 STRs) (1990)
JTM 30 (Vintage Tung Sol 5881s) (1995)
JTM series (1x12") ext cab (1995)
1912 ext cab (1997)

danmahoney

...forgot to mention that I already did try to get a couple of different quads of 6L6`s in the amp to bias within spec but they were all running too hot (25 watts and more)...
I would have loved to not have to make any changes at all and I`m definitely into 'less is more', as long as the amp is healthy...

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JCM 900 (4502) (Tung Sol 6L6 STRs) (1999)
JCM 900 (4101) (Tung Sol 6L6 STRs) (1990)
JTM 30 (Vintage Tung Sol 5881s) (1995)
JTM series (1x12") ext cab (1995)
1912 ext cab (1997)

gemather

Hell On, nice week...