Fellow Ampers,
I am working on a 67 plexi kit and I am at the stage where I would need to decide if I want to install 6550s or el 34s?
Does anyone have experience with 6550s in a plexi?
Keep in mind I do like loud and the more clean headroom = better.
Thanks
B$
67 Plexi kit - el34 vs 6550
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statorvane
- Posts: 568
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Re: 67 Plexi kit - el34 vs 6550
Not with a Plexi, but I have been through several 6550s in a SE plexi sort of amplifier; 4-hole Marshall preamp/tonestack into an AX84 SEL power amplifier..
http://s165.photobucket.com/user/JKCavi ... t=3&page=1
If you are going to go re-issue with your power tubes... I have tried both Sovtek 6550WE and Tung-Sol 6550 reissues in this amplifier. I read several reviews where people said they are the same tube. That's pure bullshit. For headroom, I'd definitely give the edge to the Sovtek over the TS reissue. Both tubes sound good, but I get later breakup with the Sovtek.
Note my voltages are around 340 plate and 290 screen. The Marshalls will be much higher. If you try this watch the screen voltages (I think 440 v is max) and your grid leak resistors should be lowered to like 100K. You'll likely have to fiddle with the bias circuit / voltage too.
I would like to see how these sound in my 50 watt clone sometime.
http://s165.photobucket.com/user/JKCavi ... t=3&page=1
If you are going to go re-issue with your power tubes... I have tried both Sovtek 6550WE and Tung-Sol 6550 reissues in this amplifier. I read several reviews where people said they are the same tube. That's pure bullshit. For headroom, I'd definitely give the edge to the Sovtek over the TS reissue. Both tubes sound good, but I get later breakup with the Sovtek.
Note my voltages are around 340 plate and 290 screen. The Marshalls will be much higher. If you try this watch the screen voltages (I think 440 v is max) and your grid leak resistors should be lowered to like 100K. You'll likely have to fiddle with the bias circuit / voltage too.
I would like to see how these sound in my 50 watt clone sometime.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: 67 Plexi kit - el34 vs 6550
Far better than eitheir tube for loud clean sounds will be to change out the two power supply filters in the first stack to two duel 100 uf cans ( each can has two 100 uf sections) so you end up with them in serise for a total of 100 uf.
If the kit does not have them, be sure to add a 220k 2 watt resistor across each filter can.
A 12at7 used for the PI tube will have a EL34 sounding as clean pretty much as the 6550, but the 6550 does take more drive signal before it clips than the EL.
If the kit does not have them, be sure to add a 220k 2 watt resistor across each filter can.
A 12at7 used for the PI tube will have a EL34 sounding as clean pretty much as the 6550, but the 6550 does take more drive signal before it clips than the EL.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: 67 Plexi kit - el34 vs 6550
When the American distributor of Marshall had them fitted with 6550's in the mid seventies, many purists complained that these amps sounded less...Marshally...The 6550 is a 6L6 based tube. It therefore has a more "American" sound to it. It will be the better choice for more headroom.