Modern Ground Schemes
Posted: Tue 05/07/19 7:48 pm
Because this topic comes up so often, here you go.
Ideal Ground Scheme:
I use a partial star ground. You can see an example of this ground scheme in the drawing I did for the lite 2b: files/JMPGuitars_18_Watt_Lite_2b_Layout.pdf
You can apply the same principles to your amp regardless of the 18 watt circuit version:
Note: all ground points on the chassis should serve no other purpose than providing a connection to earth. No transformer bolts, or board screws or anything like that.
1 ground near the Input jack covers input, pots, preamp. Ideally the preamp ground bus connects to the input jack(s) and the input jacks connects to an independent ground spot as close to the jacks as possible.
Input jacks and gain pots should have shielded signal wire. Only connect one end of the shielding to ground.
A star ground near the PT or cap can. This covers PT center taps, power amp/PI, filter caps, and output transformer (if you earth the OT).
Do NOT use a ground bus connecting the back of the pots.
IEC socket or power plug ALWAYS gets its own independent connection to the chassis.
Ideal Ground Scheme:
I use a partial star ground. You can see an example of this ground scheme in the drawing I did for the lite 2b: files/JMPGuitars_18_Watt_Lite_2b_Layout.pdf
You can apply the same principles to your amp regardless of the 18 watt circuit version:
Note: all ground points on the chassis should serve no other purpose than providing a connection to earth. No transformer bolts, or board screws or anything like that.
1 ground near the Input jack covers input, pots, preamp. Ideally the preamp ground bus connects to the input jack(s) and the input jacks connects to an independent ground spot as close to the jacks as possible.
Input jacks and gain pots should have shielded signal wire. Only connect one end of the shielding to ground.
A star ground near the PT or cap can. This covers PT center taps, power amp/PI, filter caps, and output transformer (if you earth the OT).
Do NOT use a ground bus connecting the back of the pots.
IEC socket or power plug ALWAYS gets its own independent connection to the chassis.