Jcm 800 El 34's Vs 6550's

Trick Fall

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1,139
I've had a 2204 for a long time that came with 6550's. Was considering trying out EL 34's. It doesn't seem like too involved a swap. Just wondering what people think. Is it worth doing? Easy to reverse?
 
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7,599
EL34s aren't as clean and a bit narrower in scope. Also they are easier to drive into OD.

Not too complicated to convert one way or the other. A matter of some resistors, really.
 

buddy7168

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1,142
I prefer EL34s and have converted a few amps over the years. If you’re not sure you’ll like it, I would use the piggyback resistor way first.

If you decide to keep it that way, then it’s better imo to lift the board and do the full change over. It’s not difficult but you have to be really careful not to overheat or the pads could come off of the board.

Make sure not to touch anything in there unless you know how to drain and test the caps.
 

menlow

Silver Supporting Member
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848
My ‘83 2204 came with 6550s. I tried to like them but they were too polite and hi-fi sounding to my ears. I had it changed to EL34s and I’m glad I did. It’s now got the classic rawness you would expect a 2204 to have.
 

corbs

Silver Supporting Member
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2,479
I was playing my 79' 2204 w/ 6550's Thursday night with the volume cranked and the pre-gain around 3 and it sounded amazing. I do have an '87 4010 with el-34's, but I like the stronger clean power from the 6550's that I can dirty-up with more pre-amp gain or pedal boost. Thurs night it was a low gain $30 SD-1. :aok
 

Gnarlly

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2,864
I’ve owned several 800s with both. If you are able to crank the amp loud enough to distort the power tubes then EL34s work best IMO. 6550s don’t compress and clip in as pleasant a way as the EL34s. But we’re talking extreme volume levels at this point.

To my ears 6550s sound better for lower and most other volume situations, including most venue volume levels these days. Less compression but more punch and firmer bass at lower master volume settings. The best 2204, 4104, and 4010 models I’ve owned had kept the stock 6550s.
 

Geeze

Member
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2,437
I have JMP 2203's with each - it really comes down to mood. I talked with my guru about changing out the 6550's when I first got one with 6550's but I'm glad I didn't. For straight up Marshall crunch it's the EL34's but for thick jazz or crushing Götterdämmerung with an Empress Heavy 6550's for the win.

Russ
 

Matt Dillon

Member
Messages
1,020
What speakers are you using?
You may want to try different cabs/speakers before anything else, pretty easy first step instead of having the amp rebiased etc
I believe Cesar Diaz said Hendrix used 6550’s in his Marshalls for the bass response
 

Trick Fall

Member
Messages
1,139
What speakers are you using?
You may want to try different cabs/speakers before anything else, pretty easy first step instead of having the amp rebiased etc
I believe Cesar Diaz said Hendrix used 6550’s in his Marshalls for the bass response
I'm actually cab shopping. Had been using a 70's Ampeg 4X12, but I've also used the amp with a bunch of different Marshall 4X12's over the years.
 

sdd17

Member
Messages
315
My early jcm 800's both have 6550's and I don't know if it's the 6550's or the circuit or what but those amps are so punchy and firm compared to some of my el34 amp's I wouldn't think to change anything!!
Although I would be very curious to see if the punch changes with the 34's. Mine are 50's
 

sickboy79

Member
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14,130
I prefer EL34s as well. Give it a try and see what your ears think. Easy to go back if you don't dig them.
 

oneblackened

Member
Messages
1,290
6550s are lower transconductance and require a more negative bias voltage than EL34s, so they require a great deal more input voltage swing to reach overdrive. They're also designed to be higher output power (a quad of them can do roughly 200 watts given the right rail voltage), so they stay cleaner at a given volume level. Because of all of this, they sound like they have more low end and high end than EL34s. If you want my opinion, they do different things - but KT88s sound better than 6550s for the "classic marshall sound".
 

Polvo

Silver Supporting Member
Messages
784
I like 6ca7, it gives the best of both worlds, little less mids and nice chimey highs and great percussiveness.
 

Fulldrive-1

Member
Messages
5,926
If you want tightness and headroom to run effects, 6550.

If you want to play the output stage, EL34.

if you want to split the difference, 6CA7.

When I ran 100 watt JMPs at punk rock gigs, I used Phillips 6CA7. Worked.
 




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