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previous: DonJ Ray,Come to think of it the hammond... -- 6/4/2000 12:39 PM View Thread

Re: High B+ in homebrew

6/4/2000 1:09 PM
Ray Ivers
Re: High B+ in homebrew
Don,  
 
If you decide to go the choke route, here's what I would do (DANGER DANGER): try it out first! Place the choke on the chassis, ground the case and orient it at right-angles to both the OT and PT if possible (you could get lucky), carefully connect it up, power up (preferably with a Variac) and see if it hums. I personally would rather carefully do this and find out before the holes are cut. I've used shield plates with some success, but I wouldn't depend on them to get it really quiet, Don.  
 
Or, maybe even better... how about going for a really dynamic Bassman instead? You could run two diodes, a small choke, and a cap (LC choke-input supply) off the HV secondary for a stiff 400 volt screen supply, which I think would work fine for high-quality 6L6GC's or certainly for KT88's, EL34's, 6550's, etc., depending of course on the filament supply capabilities of this PT (didn't these cabs use 6550's? - or is that a Leslie cab?).  
I assume the New Sensor OT has a 3400 ohm plate-to-plate load impedance? This will be kind of low for most everything but KT90's at this voltage (I'm assuming about 600 volts or a little less with tubes in at idle), and I think that 6800 ohms (i.e. 4 ohm tap, 8 ohm speaker connection) would pretty high for all but the EL34's; on the other hand, I personally like the sound of a lower-than-'normal' P-P load impedance (use high-quality tubes, though!). I'm just ruminating in the dark here - I don't know how faithful you want to remain to the original Bassman sound and/or how far into left field you wish to venture. Doing something that hasn't already been done a zillion times is way cool, though.  
 
Ray

 
Replies:
DonJ Ray, I finished the circut and ende... -- 6/6/2000 12:19 AM