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Running EL-34'a at lower voltages?


 
12/28/2005 2:31 PM
paulg
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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.
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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
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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,  
 
Chris
 
12/28/2005 7:08 PM
Billy R
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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
paulg
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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
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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
satamax
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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!  
 
 
Bye.  
 
Max.
 
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