Chassis grounding

I am building a wood and metal chassis for a headphone amp. There are three metal plates for the top, front and rear panel. The top and rear panel are getting grounded however how necessary is it to ground every panel? The front panel will have a potentiometer and a headphone out, both of which are relatively low voltage with the headphones getting 10Vrms on max and the potentiometer getting 2Vrms.

 

You'll probably get hum and noise if the pot body isn't connected to metal/chassis ground.

 

If you were to ask this question at diyaudio.com, they would tell you to ground all plates.

In my project, I left the front plate "float" ungrounded.

But, like @fishski13 states, you may need to run a ground wire from the pot body to chassis ground.

 

IF you can touch the metal parts and they could possibly come in contact with voltages > 50V under normal operation or in case of a failure then you should connect those parts to safety ground.

 

Another question on grounding if you guys don't mind...

My (built by someone else) Dynalo has a bipolar power supply. Now, the board looks to be Chi-fi and has a dual output transformer the +, -, and ground AC input and then +, -, and ground DC output. The secondaries are 24V and 16.4V +/- DC output.

My question is, should the center tap ground also be connected to the earth ground plug pin, as well as to the ground of the DC output, as well as connect the chassis to ground? Any danger in this?

Right now, the othe builder floated the ground. Meaning nothing is connected to the earth ground pin from the power input connecter and the center tap on the secondary is connected to the pin labeled "ground" on the power supply board AC input, as well as the DC ground output on that board is only connected to the power input ground on the amp input. If that makes any sense. Basically, nothing labeled "ground" is connected to earth ground.

 

IEC center pin is a protective earth or safety earth ground. It should connect to the metal chassis as close as practical all by itself with nothing else using soldered connections and locking fasteners. It is there as a safety measure Incase anything gets energized on the chassis. Anything metal you can touch during normal operation should also be grounded to the chassis. In normal operation there should be no current in this short wire from chassis to IEC center pin.

The power supply ground is a different connection for a different purpose. Usually this is tied to chassis at the first filter capacitor. Sometimes it's lifted off chassis ground by a thermistor in Nelson Pass' amps. Here is where you'd have everything else tied to with a bus or star ground for center taps and what not. Hope that helps.

 

Chassis ground is fine.

But what about the center tap of the secondary transformer?