Star Ground vs Bus Bar (newb)

[Hambamble]

Thanks everyone!

Phil, after reading that advice, my schematic makes more sense. It actually shows the wiring for ground, but I thought it was more of a 'guideline' and how the schematic was drawn to represent ground, rather than how to actually wire it.

The schematic groups it like this:

One ground splits into three, containing
i) Input Jacks, and preamp cathodes
ii) output jacks
iii) power tube cathodes.

The other ground is for the power supply caps, heater CT and PT-CT.

The two grounds join where the mains earth is grounded.

Thats pretty much what you described (except for the power tube grounding), which should be easy enough to swap between the two different locations if the first try is noisy.

Thanks for all your advice guys, its great to have no idea one day, then the next a bunch of strangers pool together to help and I am no longer left guessing.

[Milkmansound]

I've always kept the first filter cap far away from anything else. You can hear ripple in the bias supply even with a large cap as it is

I go fender style - preamp grounds to the chassis near the input jack, PI bias and power grounds somewhere in the middle, safety and first stage near the fuse

[Phil_S]

Phil, after reading that advice, my schematic makes more sense. It actually shows the wiring for ground, but I thought it was more of a 'guideline' and how the schematic was drawn to represent ground, rather than how to actually wire it.

Schematics will vary quite a bit in terms of useful ground scheme info. Some of simply show a ground symbol at every component to be grounded without giving a hint and where to actually locate the ground. Beware of that.

[Super_Reverb]

+1 on Voodoo's advice. My builds have a centrally located #10 bolt long enough to accommodate all my grounds. I place a ring terminal on all ground wires and separate them with washers. I use a locknut to hold the bolt to chassis and then one locknut on top.

Have had good results with Mr Blencowe's ground strategy. He groups pre-amp circuitry based on power supply connections. I run a ground for each power supply capacitor back to star. My pots and input jack are a seperate line. I also use the Marshall style input and output jacks, so that my chassis is not used as a ground conductor. Have not had any issues with this approach.

A ground buss for the preamp, pots, and input jack also works well. I think the key is to keep high currents from outputs, screen filter, and PT/OT from flowing in preamp. There is considerable gain from input jack to outputs: ground noise in the preamp become signal. Noise in early preamp stages is a bigger problem because there are more gain stages to amplify this noise.

rob.

Above sounds ok except for using transformer fixing bolt to also serve as star ground point. Just don't. If a transformer is ever removed/replaced there's no guarantee that the ground lugs will be fixed correctly. Always use a separate bolt for the ground connection. Same goes for safety ground wire.