Just finished 50 watt Dumbel102. It is fully functional after resolving some issues which I will list below
This is built in a Bassman chassis, which you can get on eBay standard drilled for 75 USD. I drilled additional holes for presence, standby and power in front. On top I enlarged one ax7 tube hole for the XLR, put the power jack in the unused power tube hole, and in the back drilled for the PAB and OD switches. It worked out pretty well. Then slapped on the worlds worst paint job.
Issues with this build were
#1 B+ power caps, problem: 22uf caps wired in wrong hole, solution: found right hole. Identified before first powerup.
#2 FET input not working, solution: wired tip to FET and ring shunt to regular input. This is different from layout/schematic diagrams.
#3 OD and PAB switches not working, problem: ordered 24v relays, solution: 12v relays. My bad.
#4 OD not working, problem used 10k pot instead of 100k pot on v2 grid
#5 OD low volume, ground issue with shield wire on Drive Pot
Mostly my mistakes, except #2. Hope this helps others.
One innovation I had on this build was to wire it so I could open the PCB to access the bottom even after doing the Pots and tubes. I used almost 50ft of wire, but it was worth it. It is still pretty quite at low volume and gets noisier when it is cranked. Order on front panel is Input, FET, Rock/Jazz, Master, Drive, Ratio, Volume, Bright, Deep, Treble, Mid, Bass, Presence, Standby, Power, Pilot. Back is fuse, input A/B, bias, output impedance (2,4,8 ohm), send/receive, OD, PAB. Transformers are NOS Classic Tone Twin for power, Bassman for output (50watt), Hammond choke and 6v power (relays). Tubes are Tung Sol 6L6GC and mesa 12ax7. Sounds pretty sweet. So may options for tone.
I have also tracked down the Hum issue on my Dumble. It seems to be related to the grounding on the input jacks and/or the volume knob. I have not worked out what to do. I had trouble wiring them initially getting no sound at all. I don't think I worked out the correct solution. I will try some alternate grounding or take the FET input and shunts out completely to simplify the wiring.
There is one more issue that I had forgotten until I saw a post on Amp Garage this morning. If you plug the speaker into the SPK1 (Switch Craft 11) the sound output is very low and the current limiter lights up like a movie spot light. If you use SPK2 (Switch Craft 12A) it works normally. I believe that the ring shunt is grounded if there is nothing plugged into SPK2, which sends the signal to ground. no good. I could be reading the wire diagram wrong, but I saw that other post on the Amp Garage and assume he did the same.
This amp has some noise problems. I built a box and mounted it. I have not had time to pull it apart as I have been doing other builds, driving across the states and snowboarding this winter. I'm going to finish my train wreck and circle back to the Dumble after that. It might be the OT phase. There is a point where the master and volume setting drops the noise level, not too loud and not to soft. So it can be played, but it is not fun.
Looks fantastic! Love the contrast with the black chassis :) thanks for highlighting your issue, will make sure the layout/schematics info is updated.
How does it sound? Any sound samples you can share?
Cheers from London
Andrea