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2xEL84 Amp Questions

3/3/2000 3:02 PM
Morris
2xEL84 Amp Questions
I need advice on setting up the output section of a Class AB 2xEL84 amp. I'm using a Hammond 270FX PT (275-0-275, 150 ma) and a Magnequest 565 OT that has UL taps. Questions below:  
 
1) Is this PT too stiff for this amp? I'd love to use a SS rectifier to save above chassis real estate, but a tube rectifier might be needed to drop some voltage. I have a Chinese 5AR4/GZ34 that I could use? What do you think?  
 
2) Should I run this amp UL or in the traditional Vox/Matchless fashion? If I do run it UL, will I have to drop even more voltage to the OT as to not overload the screen grids? Should I use screen grid resistors in a UL setup? The UL hi-fi schematics I've seen leave them off.  
 
3) It seems like a UL setup would require more PS filtering for the OT since the screen voltage is also derived from the OT. Would a CRC setup after the rectifier with the OT supply derived from the second capacitor be enough?  
 
4) The preamp will be a 6SL7 setup Fender-style. I was also thinking about a second channel (non-switchable) with an EF86 front-end. What would you recommend for a splitter? I guess I could use the tried-and-true Vox/Matchless splitter, maybe with a 6SL7 instead of the 12AX7, but might a 12AT7 setup like a Blackface be better? I also have a 6SN7 here. What do you think?  
 
5) What EL84's do you recommend?  
 
Thanks in advance for all of your help!  
 
Morris

 
Replies:
Rebel420 Before we begin, you hsould jump on... -- 3/3/2000 3:25 PM
Lee M. Based on the voltage I got on my 27... -- 3/4/2000 12:33 AM