Greetings, Friends. I'd like to share a few pics of my new amplifier.
I've been dabbling in tubes since last spring and after building a few phono preamps and power amps I figured I'd try to build a guitar amp, and where else to start but the Champ 5E1. This one's tiny, a 12x12" box made of 1x6 with a 6" Jensen Mod speaker. The Speaker had to be offset from center quite a bit to accommodate the iron on the back of the amp chassis, and the baffle is two pieces of 1/4" Fir plywood glued together. It's tight in there. Chassis is a Hammond box, 1444-12 7x5x2" but next time I'll get a 1444-14, 9x5x2" for a little more room.
I decided to mix things up by substituting the regular output and preamp tubes for their Soviet counterparts, having built up a stockpile of them through the purchase of DIY kits available from many online resellers. The rectifier tube is still the 5Y3, but the output is a 6p1p and the preamp tube is the 6N2. I had been under the assumption that the 6p1p had similar numbers to the 6v6 and built the circuit to spec with a Hammond 290ax PT and 4h choke and 8w SE OPT from a custom builder out of St Louis. All 3 EL caps are 10uF 500v and I was seeing 320v at the first cap, 315v at b+ and 310v on the plate of the 6p1p. Perfect for a 6v6, but now that I can read tube charts a little, I think the 6p1p isn't meant to see more than 250v on the plate.
So I need to drop the b+ enough to get to a safe operating point for the 6p1p. I've seen on a few forums that the old Winged C tubes can take plenty of abuse, but I don't wanna kill them early either. I've put a pair of 270R 6.5w power resistors on the HV lines going into the rectifier and that got the plate voltage down to 295v, b+ at 298v. I'm not seeing any red plating or anything like that, and the amp sounds good at the volumes I can get away with here at home. What would you do? Any other advice?
thanks!
I've been dabbling in tubes since last spring and after building a few phono preamps and power amps I figured I'd try to build a guitar amp, and where else to start but the Champ 5E1. This one's tiny, a 12x12" box made of 1x6 with a 6" Jensen Mod speaker. The Speaker had to be offset from center quite a bit to accommodate the iron on the back of the amp chassis, and the baffle is two pieces of 1/4" Fir plywood glued together. It's tight in there. Chassis is a Hammond box, 1444-12 7x5x2" but next time I'll get a 1444-14, 9x5x2" for a little more room.
I decided to mix things up by substituting the regular output and preamp tubes for their Soviet counterparts, having built up a stockpile of them through the purchase of DIY kits available from many online resellers. The rectifier tube is still the 5Y3, but the output is a 6p1p and the preamp tube is the 6N2. I had been under the assumption that the 6p1p had similar numbers to the 6v6 and built the circuit to spec with a Hammond 290ax PT and 4h choke and 8w SE OPT from a custom builder out of St Louis. All 3 EL caps are 10uF 500v and I was seeing 320v at the first cap, 315v at b+ and 310v on the plate of the 6p1p. Perfect for a 6v6, but now that I can read tube charts a little, I think the 6p1p isn't meant to see more than 250v on the plate.
So I need to drop the b+ enough to get to a safe operating point for the 6p1p. I've seen on a few forums that the old Winged C tubes can take plenty of abuse, but I don't wanna kill them early either. I've put a pair of 270R 6.5w power resistors on the HV lines going into the rectifier and that got the plate voltage down to 295v, b+ at 298v. I'm not seeing any red plating or anything like that, and the amp sounds good at the volumes I can get away with here at home. What would you do? Any other advice?
thanks!
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Very cool.
I don't know anything about the tubes you used.
But I made a very similar design using the ecc83 and 6v6, but without the choke. And a 4, 8 and 16 ohm output trafo.
One thing that I did was add grid resistors, this eliminated blocking distortion at higher volumes. I just love the way it just adds more and more usefull distortion from about 3 to all the way up to 12 (eat that spinal tap
)
One other thing I want to try is add a cathode bypass cap on the second stage for more gain.
And you can experiment with the feedback resistor, that changes how the distortion comes in. Different speaker impedanses need different feedback resistors for the same "feel".
How Amps Work
I don't know anything about the tubes you used.
But I made a very similar design using the ecc83 and 6v6, but without the choke. And a 4, 8 and 16 ohm output trafo.
One thing that I did was add grid resistors, this eliminated blocking distortion at higher volumes. I just love the way it just adds more and more usefull distortion from about 3 to all the way up to 12 (eat that spinal tap
)One other thing I want to try is add a cathode bypass cap on the second stage for more gain.
And you can experiment with the feedback resistor, that changes how the distortion comes in. Different speaker impedanses need different feedback resistors for the same "feel".
How Amps Work
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