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Re: AC30 TB low/high Power Switch


 :
5/31/1999 4:44 AM
Steve A.

Re: AC30 TB low/high Power Switch
Bob:  
 
    If the output section of the AC30 is wired up with a single 50 ohm cathode resistor for all 4 tubes (as on the schematics I have) I guess you'd rewire it with 2 or 4 cathode resistors if you were going to cut out 2 tubesó right? Correct my math if its wrong, but for the same bias current you'd want to use 100 ohms for a pair of EL84's or 200 ohms for a single EL84. BTW what value cathode resistors do you think work best with the Vox EL84 amps? Do you prefer a single resistor, two resistors or four resistors (for an AC30)?  
 
    Thanks!  
 
Steve Ahola
 
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5/31/1999 9:08 AM
Bob S

Boy what a dope I was. I completely forgot about the cathode resistor. Absolutely you need to change the cathode value or you'll burn up those bad boys. My guess would be more like 120 -130 ohm. My two EL-84 amps have these in them. But just get the ma @ 40-45 per tube and what ever value it takes to get it there. Depending on the load factor of your tubes you could go from 100-150 ohms. I leave the single resistor in there. I haven't really messed with going multiples. I've had real good luck with the Sovtek EL-84's and when I order them I order nothing above 100 value in there matching system. This allows me to keep the 47-0hm resistor in place, but I've used up to a 62 ohm resistor to maintain the ma. load I prefer. Steve thanks for jogging my memory on the cathode, wouldn't what to screw anybody up!!!  
 
Bob S.
 
5/31/1999 11:22 AM
jason

Bob,  
How's it going? My vintage 30 should be here tommorrow so I'll let you know how that amp sings with that (this is currently my favorite amp). Can't wait!  
 
Jason
 
6/1/1999 8:54 AM
Bob S

Pickin up another V30 myself. If you get a chance try it with two twelves!!! It will knock your socks off.  
 
Bob S.
 
5/30/1999 9:48 PM
Doug
Re: Suggestions
Is that the same as the one posted in the schem section here?  
Doug
 

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