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I want to build an amp with EL 84,need advice


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12/15/1999 1:57 AM
Max
I want to build an amp with EL 84,need advice
Hi everybody.  
I wrecked an old revox E36;And i have the transformers the sockets,the valves,the chassis.  
Then i want to build an EL 84 amp.  
The output transformer is about7500 omhs,which should be ok.  
But i don't know what to build.I was looking at the AC 15  
but i'm not too keen on the ef 80 pre.  
I thought also about the fender 6V6 ones,(converted to EL84),like the super or deluxe.  
The thing is that would like a lot of power amp distortion,well enough to have good compression.  
should i use a Loyez or Paraphase,dephaser?  
I'd like to have the Santana sound at low volume.  
And a good sweet blues sound.  
Any idea?  
Any kind of advice or help is welcome.  
Max.
 
12/15/1999 2:54 AM
dave rutherford

What about the matchless spitfire? - two 12ax7s, 2 el84s & 5ar4 rectifier. Single channel, vol control, tone control and post-PI master vol. A nice simple little amp design; great sounding, too.
 
12/15/1999 11:06 PM
Max
Re: I want to build an amp with EL 84,Dave have you built one?
Hi everybody,hi Dave.  
I think i'll go for the Spit.And i was wondering if you had built one.I'dd like to hear about the sound.  
And also i was wondering if i could change the 3 capacitors after the choke,for a single big one?as well,on the schem here at Ampage,it is not stated which choke it is;nor the value of the two grid 2 resistors,i guess it's 100 omhs about two to five watts;and the 120 5 watt res in the catode circuit,should be in omhs too,i think.  
But i'll be running the ot on four omhs,because it would be about 14142 omhs with eight.  
Would this,affect the tone much?  
Best regards.  
Max.
 
12/15/1999 3:29 AM
Les
Re: I want to build an amp with EL 84,need advice
go check out the AX84 site:  
 
http://www.intsys.net/ax84  
 
there are two basic designs there using the EL84, a  
single-ended desing, and a push-pull design based on  
the old Marshall Plexi circuit... I've built the  
push-pull amp, and I can testify that it kicks some  
SERIOUS butt!  
 
Les
 
12/15/1999 12:16 PM
Lee
Me too, what power tranny?
Based on my 5E3 experience, I think I need to go with a 550VCT power tranny (Hammond 270 series) but how much current capability do I need for the pair of EL84s plus 3 12AX7s?
 
12/15/1999 3:30 PM
Benjamin Fargen

Lee,  
 
Hammond 270FX 275-0-275vac 150ma for power.  
(This is a little overkill for 2 x EL84 and 3 12AX7's. You could get away with anthing 100ma and up.  
 
Hammond 1608 10w 8000ct or Hammond 125E for an output tranny.  
 
Benjamin  
 
 
12/15/1999 7:26 PM
Bob A DynaQamps

You'll need a minimum of 150 ma. for this project if you don't want to overheat you're power supply transformer. When testing recently I found that a 2 EL-84 and 2 12AX7 design under load was drawing up to 148 ma. The Hammond trans metioned will be pretty stiff and should do fine as long as the secondaries stay a 275vac.  
 
Bob @ DynaQamps
 
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