I googled a way to test the earth ground, and it said to put a voltmeter across the line and ground terminals, and it should read 120v. I did that and it does.
It tells something, but not all. Lets assume you have the "earth".
From the PS to the Bugle: +15v, -15v, and ground are connected to B1+, B2-, and ground, respectively.
From the PS to the Piccolo: +15v and ground are connected to the + and - battery terminals.
The PS ground is also connected to the case and to earth.
I've looked through your build in an earlier post. You have 3 cases: Power Supply (PS), Bugle and Piccolo. As soon as both devices connects to the single PS there is:
PICCOLOground<->PSground<->BUGLEground
together with
PICCOLOoutput-interconnect<->BUGLEinput-interconnect
It seems also that the Bugle in addition has connection to the ground through your following preamp:
BUGLEoutput-interconnect<->PREAMPinput-interconnect
In the connection there is nothing unusual, but you should see now that the resistance from the devices to "earth" is rather high and noisy:
for example - PICCOLO
- long thin unshielded wire to the PS
- shield of interconnect to Bugle, then long thin unshielded wire to the PS.
What you can do about it? The following is just my IMHO and I'm not pretending to be the one and the only truth.
- In the PS: made the distinct "one point ground". The point should have ONLY 3 wire connected: the ground from the power cord, the ground from Bugle Power supply PCB and the case. As far as I can tell from your photos - you have made the one point ground on the ground point of the PCB - please check it!
- In the Bugle: connect the ground wire from the power supply to the PCB, ground your case to the same point on the PCB. Made the power supply connection from the PS to the Bugle shielded, short and use thick wire (for ground wire for sure). Connect the shield of the power supply connection only to the one point ground in the PS. Check the quality of interconnection shield from the Bugle to the preamp.
- In the Piccolo: all have been done already by JH. The only thing I can think of - use shielded and short power supply connection like in the Bugle.
This should eliminate most of the problems, but in your environment it is preferable to add some sort of power filtering device.
