I am getting back into the hobby and recently rebuilt an old TMB I had into a Marwatt. While this is my second build, the first one was so long ago that this is effectively my first.
Once I am finished with a project, I like to document the lessons and successes so it's easier to remember for future projects.
1. Keep the DC lines away from the signal wires. Pay close attention to how OT wires are routed with respect to B+ lines.
This would unfailingly manifest as a long squeal. If the squeal was affected by volume controls, it would direct me to look at signal wires specifically. If it wasn't affected by volume controls then something was dressed poorly around the output stages.
The wire for the second filter crossed the OT secondary wires under the board. I pulled the wire from the filter and routed it along the side of the board far from the OT. This fixed the issue. When I resecured the board, the started getting a volume affected squeal. When pulled the board back up and away from the chassis, the squeal went away. This is being caused by B+ being too close to the OT primary.
2. Having a copper wire ground offset from the board works very well as part of a partial star ground setup.
I saw photos of a ground buss secured with clamps in the Marwatt download section. I decided to try it because it looked so clean. It just required some #8 copper grounding wire from Home Depot, a couple of cable clamps, screws and lock nuts.
This made organizing grounds very very easy and made this amp much quieter than my TMB. The TMB had grounds routed to a random wire all willy nilly. I will use this method going forward.
3. How to wire cliff jacks correctly and how to remind myself how they work with respect to tip, sleeve, and ground
I was used to Fender input jack wiring not because of how it was supposed to work unfortunately but because I had seen it so much over the years. Cliff jacks always gave me heartburn. Not sure why but I think I get nervous when facing something I don't quickly understand. I decided to quit ridiculous and figure it out. Super minor and borderline ridiculous but I learned how to troubleshoot and prove things to myself using basic tools and fundamentals. It makes things more intuitive for the future.
4. Keep wires short especially signal wires
Signal wires are little antennas. Keep them short as possible to limit picking up noise. I knew this but it was good to see a reminder in real time.
5. Keep turrets close enough together to make mechanical wrap around connections with component leads.
I purchased a custom board from Hoffman for this build and specified the turrets to be placed a little too wide across the board to be a half wrap around them. I prefer wraps because I prefer to bring under board B+ wiring up through the turret. This allows for both components and underboard connections to have solid mechanical connections.
6. Keep plate resistor turrets really close together to limit proximity of resistor leads and connections to signal wires (ala Leo Fender)
I would run into signal wires being too close to B+ wires and there would be squeals. It now makes sense why Fender has their plate resistors on eyelets half way across the board. It physically limits the areas of inductance and allows for more effective lead dressing and less noise. I'll copy this going forward.
7. Fundamentals, fundamentals, fundamentals!!
I struggled with using cliff jacks this go around because I am just not used to them. I would wire them, realize they were wired backwards (pins 2 & 7 were wired to the sleeve), pull them out, "re-wire them" only actually just wire them back the same way, and generally just stay stuck in my head.
After taking a breath, understanding properly how a signal gets from the guitar to an input stage (grid leak resistor, impedance setting, etc) I proved to myself what the correct wiring should be with a cable, a multimeter, and a little patience with myself.
I finally got them wired correctly and put in. There was still a persistent problem with one. It would hum loudly when plugged in and my guitar would be faint behind the hum. I knew I wired it correctly so maybe there was a connection issue. Sure enough, there was a cold solder joint on one of the ground connections. I reflowed solder and the problem was instantly solved.
When in doubt, go back to the fundamentals and trace your steps.
I know this is long winded but in case anyone is having any trouble, this is what I learned. Hopefully it can help other folks too.
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