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Running EL-34'a at lower voltages?

12/28/2005 2:31 PM
Running EL-34'a at lower voltages?
I have a Plexi clone that runs about 450 volt B+. I'm intrigued by the Germino Club 40, bacically a JTM-45 that runs at 415v. Any ideas or experiences for running lower voltages with EL-34's? I'd like to get that plexi compression without all the headroom (join the club, huh?). thanks
12/28/2005 2:44 PM
Dai H.

Maybe you'd like a lower voltage PT. Some Marshall 50Ws have low B+, around 395V to as low as around 350V (some have reported). I have an '80 2204 which has the lower B+ (about 395V), and it seems to be smaller but sweeter sounding than the later ones w/higher B+ (430-450V depending on wall voltage, biasing). I think Marstran had a 350V 50W PT (on sale for a couple more days 'til the end of the month IIRC). Otherwise Mercury Magnetics (good quality, higher priced), or a Hammond or something if it doesn't need to be the standard dimensions/mounting, etc. I recall reading some article w/one of the Scorpions guys (Mattias Jabs?), and from what he was describing, it sounded like he liked these lower B+ 50Ws rather than the 100Ws.
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12/28/2005 3:07 PM
Chris/CMW amps

Hi Paul  
Dai did post some excellent suggestions!  
40 Watts will just be slightly "unlouder" than 50 Watts so if you wanna get that tone at lower levels while using a high quality OT (let's say OEI or MM) than use a so called post pi mv (replacing the biassplitter resistors with a dual ganged pot).  
Hope this helps,  
12/28/2005 7:08 PM
Billy R

Paul: I just finished a custom amp for a customer and it uses EL34's that run at 395 volts (with a 5AR4 rectifier). It is a fixed bias amp, and uses the Weber W025130 power transformer, and a 35 watt, 3500 ohm OT. The clean output is 28 watts, and it sounds great. Still a loud amp, but not so loud that you can not turn it up.
12/29/2005 7:22 AM

Great advice. I'm hoping to get that great EL-34 tone without the huge volume. Presently, I can't get output tube breakup until the amp is about half way up. I guess I will have to reconsider the OT , a MM 50wt Plexi, too.
12/29/2005 8:00 AM
Ian Anderson

I used to own a '76 Marshall 2x12 (non MV), it had around 350v to 375v on the plates and broke up fairly easy.  
I could crank that thing full up & balance out with the natural volume of the drums. It had that Highway To Hell AC/DC tone :D  
... Ian
12/29/2005 8:44 AM

Hi everybody!  
Paulg, a daft idea which wouldn't cost too much would be to buy a variac, and use that to lower your B+ to see if you like it before wiring another trany in!  
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