Hey,
I just got an old JCM900 combo, it needs re-wiring and I was thinking of getting the tubes replaced, I was wondering what good quality tubes would get decent distortion out of it? (I got it off my dad, he used it when he was younger and in a band so it's pretty damn old!)

Cheers!

www.dougstubes.com

jj el34's for the poweramp, and jj ecc83s's and or sovtek 12ax7lps's for the preamp.

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What about the groovetubes GT 6550 R tubes and for the preamp 12AX7C groovetubes?

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and / or? You can mix and match different types?

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in the preamp yes you can mismatch brands(sovtek, jj, GT,ruby, ect...) and types(12ax7, 12at7, 12au7, ect...)... in the poweramp no, not without some serious modding.

you'd have to mod the amp to take 6550's.

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Did you just pick any two tubes you could find?

Thanks for your help guys!

Well kind of, yea but also they r the ones zakk wylde uses

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he doesnt play jcm 900's... his 800's are modded for 6550's though.

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But how do you mod the amp? And im not sure if you have to cos it says its a replacement for marshall, hiwatt etc

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You cant mod yourself,you get it done profesionally,like at voodoo mods,ect.They all take different tubes,anyway.

jcm 800's were designed around el34's... which are completely different tubes from 6550's. the 6550's are much larger and higher power tubes. for example the 120w engl savage 120 runs off of only two 6550's, where as the savage SE runs 120w off of four el34's. so for an amp like a jcm 800 or 900 to take 6550's you need to have it modded for them to work properly.

there are some amps though that need little to no adjusting to take a number of poweramp tubes, like some mesa. and pretty much all thd amps can take ANY standard power tube in production today. but marshalls no...

from there, you also have to consider that the tubes you're talking about(6550) compared to the tube that he should be using(el34) are going to give him the opposite effect of what he wants. as kt88/6550 type big bottle/high wattage tubes are going to give him more headroom and clean up the sound a little. where as el34's are known for early breakup and sweet poweramp grit.

and just because an amp can be adjusted to take a certain tube, doesnt mean it should be. as the jcm 900 was built around the el34 tube.
there was a period of time when the el34 dealer marshall went through shut down so they started loading them with 5881's and 6l6's. so you have an amp designed and voiced around el34's loaded with a different kind of tubes. and anybody that's ever played a 6l6 or 5881 loaded jcm 900 and a el34 loaded one should be able to vouche for me here, the 6l6/5881 ones SUCK and that's why jcm 900's get a bad rep.

so it's not to say that 6l6's 5881's, and 6550's suck... it's just that the jcm 900's werent designed around them, just modded to take them.

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You know your shit.

Thanks man that cleared it up. and yea fuck you know your gear! Still one day im gonna get a Marshall JCM800 and stick in some 6550s wylde style

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get your self a jcm 2000 dsl 100, more distortion, has a clean channel and its more versatile.

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If I had the money I would, as it was this was free so I wasn't going to turn it down, i'm skint atm! My first tube amp

Yea well right now im waiting for my ZW set to arrive. its been over 1 fucking month!!!!!!!!!!

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Metalhead is right, the 6550 tubes are the highest gain, highest output power tubes. At least from what I understand about them.

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.....

someone hasnt been paying attention.

okay... 6550's are powertubes, preamp tubes are where you get most of your gain from. the powertubes will only give you distortion when the amp is ran really hard.

6550's can be ran at much higher wattage than el34's, thus making them CLEANER powertubes with more headroom....

regardless, a jcm 900 is going to need to be modded to take 6550's. but if you're looking for lower headroom in the power section, you'd want to stick with el34's anyways.

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Well, my amp is off to the doctor's, I'm going with the jj ecc83s's and sovtek 12ax7lps's xdx suggested, can't wait for Tuesday!

Why are you sending it to the doctors?Your ment to send it to a guitar tech.

Tuesday is a pretty quick turnaround to get an amp re-wired and tubed.

"The doctors" was a joke, but i'm sure you got that

Yeah, the guy I know doesn't do many so he has a fair amount of time to piss about with 'em, he picked it up yesterday (Thursday), should be back Tuesday, I'm very excited!

Yesterday was saturday?

rewired? you mean rebias'd?

biasing is really easy and not very time consuming for any experienced tech, and "tubing" just consists of putting the tubes in the sockets, which is about as easy as putting your weiner in a girl.

i mean, i took one of my amps to my local tech for a retube and bias, aswell as a good cleaning, and a look over to make sure nothing looks wrong. took her in tuesday he had it done the next day because he wasnt really busy with other amps.

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