I decided to try my hand at a preamp in a small chassis. I had this old chassis with lots of holes in it so I simply built a turret board and put 2 tubes in it. No switching, no extra tone stack switches, just a Hybrid preamp. I used Doug Hoffman's tube pedal power supply which works really nice.
Here's the schematic. I'll try to get some pics soon.
Still tweaking. The treble control is not as effective as I'd like, meaning somethings killing the highs later in the ckt. Also the output is too hot so I'll be adding a voltage divider to reduce the output. I currently using a 12VAC 1000ma wall wart to power the torid. I get 12VDC for the heaters, regulated and about 310VDC for the B+.
Once I nail the tone it'll be easy to move this to a new chassis.
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Last edited by Bob-I on Tue Apr 11, 2006 7:24 pm, edited 2 times in total.
FWIW, I ordered a Zendrive from Alf Hermida, waiting for shipping charge, but Alf also recommended the BSIAB 2 pedal ( Brown sound in a box ) . I think I'll build one and see whats it like with Dumble clean channel.
ahhh k... i understand that then:) i have always just had a thing against pedals... just like a guitar and amp.. although those pedals sound amazing...
I need to rework my amp for a little more gain in the OD channel, right now im using the od network layout from norms ODSreverb, i need to put in the one that uses a pot to adjust...
I'm gonna be waiting ( for a long time I think ) for a Zendrive I'm trying to order, but I guess its a cascaded mosfet design with maybe a dumble style post OD tone shaping EQ.
would love to capture that dumble OD sound at low volumes with a pedal.
Doesnt beat the real thing - tube amp running nice and open, though.
I recorded some with the preamp today, plugged into my Weber kit Super Reverb, all tone controls on the amp set on 5. It doesn't sound much different than a fuzz pedal to me.
I'm gonna be waiting ( for a long time I think ) for a Zendrive I'm trying to order, but I guess its a cascaded mosfet design with maybe a dumble style post OD tone shaping EQ.
would love to capture that dumble OD sound at low volumes with a pedal.
Doesnt beat the real thing - tube amp running nice and open, though.
cheers
Pete
Hi Pete,
It actually approaches the tonality, and a little bit of the feel, but I've never played the real thing (just some clones). I'll try to do a recording in the next week or so. I'd certainly recommend you give it a try, though I'd use JFETs instead of MOSFETs, since you can bias them more easily. Also, if you follow the dumble topology, MOSFETs will give you way too much gain. Shoot me an email if you want some help with this. I have a fair amount of experience, though limited electronic understanding.
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