JMP 2203 - EL34 vs 6550

eyeshredbmx said:
Both sound great. Minor nuances, maybe slightly more low-end response with 6550s due to the headroom. I feel like EL34s put out plenty, though.
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Oh they do. Crank 34's between 4 & 6 MV and the midrange grind turns to buttah.
 
braintheory said:
I far prefer EL34’s in them (or even 6L6GC’s like in my ‘69 plexi, which sound awesome btw). With 6550’s the response is slower than with EL34’s, the attack is slightly rounder (even more so with KT88’s) and you sacrifice center and uppermidrange growl and kerrang (both qualities that really define much of the signature Marshall sound to me). Those frequencies will get smoothed out. You do, like others said though, get a deeper low end and more headroom. To me it’s a poor trade off for where Marshall’s excel

I have currently a 1979 JMP2203 with GE 6550A’s now in for a mod and getting switched to EL34’s. Should come back much improved
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Pretty much how I feel about them.

One thing to note about 6550s, they really don’t like a lot of plate voltage on the screens. 250-300V max.

One thing I do like about 6550s over EL34s - as master volumes get pushed way up, mids typically get filled out which if you’re going for a scooped metal sound can be aggravating. 6550s tend to sound better at much higher volumes as they’re naturally scooped so they sound much better for high gain high volume scooped mids metal in Marshalls.
 
glpg80 said:
6550s have a bigger sound to them but are less musical - it’s like a V shaped tube EQ. In the room it’s a broader sound but under a microphone they’re shrill and hollow.
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No they are not shrill and hollow under a microphone….unless you don’t know how to record I guess. Its not this HUGE difference you guys carry on about in Marshalls.
 
Greazygeo said:
No they are not shrill and hollow under a microphone….unless you don’t know how to record I guess. It’s not this HUGE difference you guys carry on about in Marshalls.
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They’re shrill and hollow in person. I keep a 6550 loaded Marshall around - it’s not like I don’t run the tubes. It’s a big enough difference to discuss about. Go run EL84’s and tell me the power side doesn’t matter.
 
glpg80 said:
They’re shrill and hollow in person. I keep a 6550 loaded Marshall around - it’s not like I don’t run the tubes. It’s a big enough difference to discuss about. Go run EL84’s and tell me the power side doesn’t matter.
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I think that may be your particular amp. I've had 2 6550-loaded 2204's over the years, and shrill and hollow are not words I would use to describe them. "Big" and "Bold" and "Tight" more come to mind.
 
eyeshredbmx said:
Heck yeah, is that Friedman mod?
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SonVolt said:
I think that may be your particular amp. I've had 2 6550-loaded 2204's over the years, and shrill and hollow are not words I would use to describe them. "Big" and "Bold" and "Tight" more come to mind.
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They’re shrill and hollow compared to EL34s. On their own I totally agree they’re wide sounding, big and bold. Tight is relative to preamp design.
 
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