I've been struggling with some sort of grounding issue with my first 2 CBG builds and its been driving me mad. Had both to bits several times now and still haven't been able to get to the source of it until today......
Was once again checking the connections inside one of those CBG's, but this time plugged into my little Orange battery/mains amp and was surprised to find that there was NO buzzing when I wasn't touching the strings and no 'clicks' when I touched any of the string contact points (bridge, tuners etc.) I then plugged into my recently bought (used) Roland Cube 20x that I'd been trying my CBG's through and that buzz returned with a vengeance! Then decided to check some of my Strats through the Roland and got that same buzz. Exactly the same was happening with the little Gibson/Baldwin amp. I'd bought for my wife to use with the CBG I'd made for her. Every guitar I tried exhibited that buzz. As a final check, I ran both CBG's through my 60w Johnson Mirage and they were all totally buzz and click free.
So I've been slowly going mad wondering why I hadn't been able to earth my 2 CBG builds successfully when it appears that the cause somehow lays with these two little amps.
Does anyone have any clues as to why these two amps impart an 'earthing buzz' to guitars? I'm a bit lost.....
I've built a couple of "mason jar" speakers for my CBGs, partly after looking at cheap "practice amps" and finding this is a fairly common problem with them. Cheap amps get buzzy. I can't address the particular brands you name, other than noting the "used" condition of the Cube is suspect and may need repair. You can open up the Cube and look for exposed wires or deteriorating connections, maybe you can simply use a glue gun in the interior to make sure wires and connections are insulated from each other. I'm unsure of your soldering skills: you could add a resistor across the input and input ground of each channel in the amplifier, just like you might put an orange drop resistor in an electric guitar or bass- but this is geeky electronics stuff- I don't know how far you want to involve yourself in this.
There's tons of information online about solving these issues as amplifier repair or in building homemade amps. As you have found out, this isn't actually a CBG issue. It's an amplifier issue. It's just more sensitive to the more primitive electronics in CBGs. It's also a reason why I've found it very worthwhile to build my own amps from a kit. It's quite a learning experience.
Thanks for your thoughts on this issue, Christopher. My soldering skills/electronics ability is very rudimentary and limited really to just changing tubes and cleaning scratchy/stiff pots., so I'll probably not tinker around the insides of those amps.
On the plus side, at least I now know that there isn't a problem with my wiring & earthing on these first CBG builds and it hasn't put me off building more!