can i run 6550's in my marshall 30th anniversary?

[the_bleeding]

Im curious. I'm really into modding and experimenting these days and straying from dogmatic amp practices. Plus i hear marshalls sound badass with 6550's. So do you guys think its possible?

I posted this at harmony central but i dont expect that thread to get far.

[northlane.josh]

i would email rich @ eurotubes.com
he's extremely knowledgeable and will be able to give you a good answer & recommendation,
I suggest him because i dont know  :(

[the_bleeding]

hmmm thats an idea... but i dont really trust him. He likes JJ's alot and i dont  :lol:

[Roobubba]

There are a lot of knowledgeable amp dudes on here (not least Martinw, of course, but there are others well placed to be able to answer). I'm sure some of them will be along soon :) Sorry, I can't be of any help!

Roo

[hamfist]

Not familiar with that particular amp, but a google search showed me that early ones came with EL34's, later ones with 5881's.
  An EL34 Marshall should be fairly easy to convert to 6550's with a change of bias splitter resistor (and possibly a change of bias range resistor also). But ....A key thing to note is that 6550's also have a greater current draw than EL34's and will therefore ask more of your power transformer. If the PT is built sufficiently over spec for the amp, then that should be fine. if the PT is only just up to the job of supplying the amps needs then a little bit extra demand might be too much.  I'd get some advice from folks about this particular amp if I were you. All the '70's JMP's and JCM800's (2203/2204) were fine with 6550's (in fact the American-sold 2204/2203's had them installed as standard). 
  Your amp probably woud be OK, but it's best to find out from folks who have a bit more specialist knowledge of the 30th Anni. amp.

[martinw]

What he said.

Be careful, because some early 90's Marshalls had trannies that were barely adequate.
4 x "a little bit extra"  might equal 1 x "just a bit too much."

[the_bleeding]

i have the 6100lm version (5881 version). Its my understanding that the only difference between this and the regular 6100's was they modified the bias and heater circuits of the power tubes so it could run on 5881s, reason being this amp was in production right as el34 production stopped.

i actually emailed Marshall about the power transformer specs, they've always been a huge help to me in the past, though they take forever to respond  :(

[HTH AMPS]

best way to tell if the PT isn't happy with the extra current draw is to measure the heater voltage - if it's around 6.3vac as you'd expect, I'd say you're ok.  if it's being dragged down below 6vac I'd say not to go there.

of course you could always run it on just two 6550s and get the tonal benefits while staying within know limits that the PT can handle.

I can't imagine any situation where a pair of 6550s in a Marshall isn't loud enough.

[the_bleeding]

best way to tell if the PT isn't happy with the extra current draw is to measure the heater voltage - if it's around 6.3vac as you'd expect, I'd say you're ok.  if it's being dragged down below 6vac I'd say not to go there.

of course you could always run it on just two 6550s and get the tonal benefits while staying within know limits that the PT can handle.

I can't imagine any situation where a pair of 6550s in a Marshall isn't loud enough.

hmmm, i think i'll try that. And if i have to do 2 tubes, i'll just hit that half power switch i have :D