mhelin
Well-known member
When I noticed the title I was expecting a SE output amp. Are there any SE (or DSE) Dumbles out there?
Dumble inspired Fender Champ build
- Thread starter Potato Cakes
- Start date
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Potato Cakes
Well-known member
Well, I couldn't leave well enough alone. I wound up finding another similar circuit build that had the same tube compliment and layout that I was using. I pulled out the old board and started over. Along the way I may or may not have discovered a number of issues that caused me to like the amp at first then slowly not like it as much. There is only so much a project and take a bunch of resoldering before you start to create additional circuit errors. Regardless, the newer circuit has a lead channel mod which was something that I was trying to incorporate to a degree in the first place. I also made the Extra Sprinkles function as a High/Low input switch. The Master Defeat switch has been repurposed to taking the tone knob out of circuit.
I didn't get a chance to test it tonight as I spent a bunch of time chasing down a problem with the B+1 voltage leaking to the cathode on one of the 6V6GT's, which caused the power output tube cathode bypass to explode. Somehow, there was about 220 ohms of resistance between Pin 3 (plate) and pin 8 (cathode). When I pulled the tube, it went away. I put the other tube in the problem returned. The pins on the tube socket are not adjacent which ruled out the rare possibility the socket had a failure with pins making a connection inside the moulding. I could not find any stray short or other issue so I started pulling components off of the socket and then the problem went way. I put everything back in place and the problem was still gone. I generally don't like it when problems solve themselves, but as long as I don't do anymore work on this circuit I think it will be good. I did a quick test and it's very quiet and the tone knob now seems to function as one would expect. It also seems to has much output as I would expect a 15W amp to be able to deliver. I'll mess around with it tomorrow and report back. So now, this project has been completed. Seriously this time...
Thanks!
Paul
I didn't get a chance to test it tonight as I spent a bunch of time chasing down a problem with the B+1 voltage leaking to the cathode on one of the 6V6GT's, which caused the power output tube cathode bypass to explode. Somehow, there was about 220 ohms of resistance between Pin 3 (plate) and pin 8 (cathode). When I pulled the tube, it went away. I put the other tube in the problem returned. The pins on the tube socket are not adjacent which ruled out the rare possibility the socket had a failure with pins making a connection inside the moulding. I could not find any stray short or other issue so I started pulling components off of the socket and then the problem went way. I put everything back in place and the problem was still gone. I generally don't like it when problems solve themselves, but as long as I don't do anymore work on this circuit I think it will be good. I did a quick test and it's very quiet and the tone knob now seems to function as one would expect. It also seems to has much output as I would expect a 15W amp to be able to deliver. I'll mess around with it tomorrow and report back. So now, this project has been completed. Seriously this time...
Thanks!
Paul
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There was a fairly simple homebrew D inspired circuit, by a guy called Mat on The Amp Garage site about 13 years ago. It was called 86 Special.
Reduced D front end into a simple SE power amp.
12ax7 » ef86 » el84.
I rolled a similar one with a 6sl7 front end out of curiosity. Still have it somewhere, I recall it worked great with 50s ∫ 60s P90 guitars like Gibson or Mosrite giving a unique growl. But You have to like the SE overdriven sound. It seemed a bit one–dimensional to me. I found more response in an old 50s GA40, which kind of puts a perspective on it.
