The Amp Garage

Attached final Layout and Schematic.

Note - Layout does not include Clean Channel Master volume - but that is easy enough to add between the OD drive and Reverb Dwell pots on the back of the amp. Layout is 95 percent correct. Always reference schematic.

Spent some more time dialing it in, and then stuck it back in the headshell I built for it several years ago. Need to make some final adjustments to the cab but i'm very pleased with how it turned out.

Tone is amazing, will post some decent recorded clips when i get back in a few weeks. Stay tuned!

Solved! Long story short, between performing the PI balance procedure and moving around the PI grid input wire the noise is entirely gone! Amp sounds absolutely bonkers. I need to get the FET preamp working, so will report back when i get there. Filters do indeed load the circuit down quite a bit. B...

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So update to this - I was able to bring it up safely today - got the pair of KT120s biased up and so far, so good. The only odd thing I've encountered so far is when I turn the master volume up past 10'o clock on the knob i get a loud 10Khz squeal. This noise goes away when the master volume is turn...

Power tube plates and screens, HV CT tied to ground lug on rectifier tube sockets

Power tube cathodes grounded to ground lug near power tubes

Heater CT attached to top of cathode resistors

Everything else connected to main ground buss, terminated to point next to input jack

Sounds fantastic. Great job!

Done and dusted boys and girls! I added clip leads to the various filter caps and just moved them around until i got the lowest noise floor. The amp is reasonably quiet now and sounds fantastic! Moral of the story is reflow all your solder joints and elevate your heaters

Dirty ol' center tap! You might be able to get a further reduction in hum by tying your heater CT to your power tube cathodes for some heater elevation, go easier on the cathode follower section as well. As long as you are fully bypassed it should be a nice clean elevation voltage. This is my next ...

follow by oscilloscope where buzz starting with input jack normally grounded and report here, after anode capacitor , scope AC coupling. (did you make ground on input jack switch contact to gnd when is no jack in- this can cause loud humm?) And, another mystery solved - I reflowed the center tap on...

follow by oscilloscope where buzz starting with input jack normally grounded and report here, after anode capacitor , scope AC coupling. (did you make ground on input jack switch contact to gnd when is no jack in- this can cause loud humm?) So i tried to do this, but my scope is not doing a great j...

Ok, so i moved all the filter caps back to their original location, and ran a buss wire that just connects all the filter cap grounds together like I see in matchless gut shots. This connection then goes back to the rectifier socket solder tab that connects to chassis. Still a buzz when i turn up ei...

Looking at layouts of Matchless amps, and the Trainwreck Rocket it just seems like the filters cap ground are all bussed together and connected to a ground point near the rectifier tube? How do they get away with that? lol.

what is the orientation of the output and mains transformer? (main transformer can be major cause of humm) Power and output transformers are close to each other, with laminations oriented 90 degrees from each other. Chassis is a 90s era Vox AC30 chassis. In it's original form it did not have mains ...

locally is better but you need to follow currents in the ground, you cannot just connect preamp gnd node to the main filter rectifier node (biggest currents there). need to follow the distribution stream. also how many chassis gnd points you have (should be only one, close to input jack)? Where wou...