Metropoulos Forum

Should I go with the old style of grounding by running the buss on the back of the pots? In my 18 watt build I ended up with a ground loop and had to use a very different grounding scheme. Do all you guys pretty much do it the way the originals were wired or do you hang a ground buss off of the turret board or do you.....

Thanks,
Chris Stokes

Hey Chris, if using alpha or cts type pots I always ground with the rail across the the back of the pots and rarely have trouble as long as you get a good contact all the way round ,good joints [and not the kind your thinking]LOL, you know what I mean, good luck with it.

One method i've seen used by guys on the 18 watt forum is to take a fairly hefty gauge copper rod and flatten the ends off and bolt it to the chassis so it runs most of the chassis length. All of the grounds other than the mains cable ground are hooked up to that buss rod.

I like to use a ground buss on the board itself, which I do by adding an extra pair of eyelets and then soldering a piece of thick tinned copper wire between them. Anything in the preamp that needs grounding is connected to this, and then a single connection runs to the cap can which serves the preamp and then to the chassis ground point.

It reduces the chance of getting a ground loop through the pot cases and gives you the flexibility to ground it where you want to the chassis. It also means there's no chance of damaging the pots through soldering to the cases.

This isn't the clearest example as it's a busy amp but here's how I did my 2550:

There seems to be a lot of mystery about grounding....
A lot of the layouts you see just show arrows for sections that need to be grounded, but they never show you WHERE to ground it.

For my first JTM45, I stared at pictures of old JTMs and tried to put every wire in the same spots as in the pictures and did grounding the way I thought I saw it in the picture. The amp has no hum at all.
After that I started reading about grounding and started trying other ways, trying to do it following 'the rules' and they never turned out as silent as that first JTM45...

Recently I ran into trouble big time with a Superlead because of my grounding. I was using a bar on the board and several connections to the chassis in what I thought were correct places, but the thing hummed like hell.

So I removed grounding and went back to old-school Marshall grounding as much as possible and the amp was dead silent!

So, no more grounding rules for me, I solder a bar to the back of the pots, connect all sections from the board to it and ground cans to their resp. bolts, figuring that's the way Marshall got away with it for years, so why can't I

What gauge is best to use? Where are you getting the buss-wire from? Would they have something at Lowes/Home Depot?

Double post.

I get it from a wire company. I'll send 18 and 22 gauge.

I'm not sure if Lowes or HD would have suitable buss wire. Anyone know?

VG

not at lowes or home depot the best you can do is the household wire. Usually the smallest quage is like 14.
~CS

I got you answereing in to different posts. Thanks Goerge.

My new build is coming slow but steady. 'Can't finish soon enough.

do you have any pics of an historic correct grounded marshall amp?