Ground connection for proto TPA3251 kit?


2012-10-28 1:30 am
My first time wiring up an amp and would appreciate some advice on the safe approach.
The TPA and SMPS are mounted side by sideon a plywood base with a plexiglass cover. There is also a iec plug with switch and fuse. How should I connect the grounds (from the IEC plug, the SMPS power supply, and the ground wire from the balanced input of the amp... there is also a shield wire on the neutrik XLR connector)

See, when you build a "proto" of an amp, you want to rule out problems for the final build. So you need realistic conditions. The aim is a silent amp and safety as forced by the rules / laws.

The final build will be in a screening case. You can not solve grounding problems with a wooden case, as it does not conduct and shield. Your wood/plexi case may be dead silent, while the final case hum´s like crazy with the same connections.

In the end, if you use a metal case, (depending on the safety class) the mains ground will connect to the chassis. The power supply´s ground should connect to it in some way, too. How, this is the quest.

Basically there should be a central audio ground and a mains ground.

The 4th contact of the XLR connector will touch the chassis and mains ground.
The ground pin of the XLR should only be connected to the amp ground.

Simple rules, but how you end up, to find this out, you need this realistic build...

So we are at my first reply, again.

PS with D-amp and a SMPS there is always RF problems. Just connect it to source and speaker and use a transistor battery radio as detector. You will be surprised what you receive around an "open" amp!
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