tunghaichuan
September 11th, 2007, 01:01 PM
Just a heads up for anyone looking for a beginner's tube amp project.
I'm going to build this amp in the near future:
http://web.mac.com/calhoun/PCB/Firefly_PCB.html
I just got a Rev. 4 board from John from the above site, and it looks promising. A while back I built a Firefly amp on an eyelet board but I never could get it to stop from squealing at high gain settings.
The Firefly is a 1W tube amp using a 12AU7 in push pull operation. The low gain preamp is a two stage cascaded 12AX7. The amp has a boost switch and gain control which really makes that little sucker crank. The boost is accomplished through a cascode 12AX7 circuit that really provides some over the top gain.
The problem with this amp is that there is so much gain on tap that it squeals if built using an eyelet board a la Fender. According to a couple of build reports, the PCB solves this problem and is dead quiet.
The build cost comes in at around $200US. The parts are available from Mouser and Antique Electronics Supply. The chassis can be fabricated which should save a few bucks.
PCB construction is more delicate than eyelet or turret board construction, so take care when soldering the PCB.
I don't have any connection with John Calhoun other than being a satisfied customer. I got the board quickly after I ordered it; the transaction couldn't have been smoother.
tung
I'm going to build this amp in the near future:
http://web.mac.com/calhoun/PCB/Firefly_PCB.html
I just got a Rev. 4 board from John from the above site, and it looks promising. A while back I built a Firefly amp on an eyelet board but I never could get it to stop from squealing at high gain settings.
The Firefly is a 1W tube amp using a 12AU7 in push pull operation. The low gain preamp is a two stage cascaded 12AX7. The amp has a boost switch and gain control which really makes that little sucker crank. The boost is accomplished through a cascode 12AX7 circuit that really provides some over the top gain.
The problem with this amp is that there is so much gain on tap that it squeals if built using an eyelet board a la Fender. According to a couple of build reports, the PCB solves this problem and is dead quiet.
The build cost comes in at around $200US. The parts are available from Mouser and Antique Electronics Supply. The chassis can be fabricated which should save a few bucks.
PCB construction is more delicate than eyelet or turret board construction, so take care when soldering the PCB.
I don't have any connection with John Calhoun other than being a satisfied customer. I got the board quickly after I ordered it; the transaction couldn't have been smoother.
tung