Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Toxophilite on March 04, 2014, 10:57:33 am
-
So my friend, the recording engineer, wants me to help him build a bass amp. He saw and heard my various creations when recording and he liked the sound and kooky nature of them and wanted to build his own unit.
So the other day I picked up a Hammond E-100 series chassis.
It's a 2 power amp unit one being 2 7591 with a GZ34/5Ar4 rectifierthe other being 2 6WGB with a 6CA4 (the 6wGB reverb amp will likly be gutted and save i'll save the OT and chokes)
lots of 7247 tubes in front of these as phase splitter etc.
No preamp on this unit
All the tubes except for the 6CA4 were sold off by the organ killer I bought it off.
Here's the main part of the amp schematic
http://www.captain-foldback.com/Hammond_sub/schematics/eseries/E100F30a.GIF (http://www.captain-foldback.com/Hammond_sub/schematics/eseries/E100F30a.GIF)
I know it's general policy to use some things as is (power amp , power supply)
but I've done that and completely rewired with some success at both
My friend was keen on a bassman style and I'm familiar with some of the fender idiosyncracies. Also whilst 7591s are now reissued by JJ the 7247s are still hard to get believe and so I'd have to rewire the phase splitter anyway(or at least half)
SO
I've read the 7591 power amp could be rewired to take 6L6s (maybe not GC but 5881 or GA/GB)
What say the gurus on this?
Is there any point in it or should I just put a Bassman front end in front of the two 7591
I tested out the power tranny and seems to work fine and supply the necessary voltages. The schematic voltages seem pretty close to ehat a 6L6 might require. and I would probably use a solid state rectifier as it's a bass amp and I'm not that keen on sag anyway.
-
(the 6wGB reverb amp will likly be gutted and save i'll save the OT and chokes)
That would be 6GW8. The reverb amp is almost identical to the AO-44 that I converted to my Pee Wee amp, except it has no PT of it's own.
http://home.comcast.net/~seluckey/amps/PeeWee/PeeWee.pdf (http://home.comcast.net/~seluckey/amps/PeeWee/PeeWee.pdf)
-
Oops
Yeah I got that backwards
I don't have the tubes and they're pretty pricey allegedly
I read they were like 1/2 a 12AX7 and an EL84 in the same bottle
I'm definitely going to yank the OT and the choke and keep an eye out for an appropriate PT
Maybe I could mount it on my other Hammond chassis for a stereo geetar amp...hmmmm