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TM3030 - Grounding of casing recommended?
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author TM3030 - Grounding of casing recommended?
yves
Hi everybody

I successfully built the TM3030 and I must say it really sounds amazing!

Now I am building a casing from extruded aluminium sidepanels and cnc-milled aluminium sheet metal.

My question now: Is it advisable to connect the aluminium casing to the PCB's zero-volt testpoint, or are the board mounting pads already connected to 0V (I will mount the board via hexagonal metal PCB standoffs to the aluminium casing)? Is it a good idea at all to connect the casing to the board's 0V?

Cheers,
Yves
Synthbuilder
yves wrote:
Is it advisable to connect the aluminium casing to the PCB's zero-volt testpoint


Any metal casing should be connected to 0V.

If using an external wall-wart for your supply and you are using a plastic output jack socket, I tend to recommend using the midi out socket's sleeve connection (see page 17 and 18 of the Builder's Guide). If your midi socket is a metal one it will make contact with the case and provide a reasonable grounding bond. It's a good idea to use those toothed washers to stop the nuts from coming loose as well as providing a good electrical contact.

Grounding may be also provided by the audio output jack socket if you have used one with a metal mounting bush (eg. Switchcraft 112APC types). You don't then need to make the sleeve connection on the midi socket if you have a metal output socket as only one grounding connection needs to be made.

If you have used plastic midi and output sockets then connecting a wire from the GND pad to suitable screw, nut and washer on the case will be best course of action.

For an internally mounted mains supply you should ensure that the case is bonded securely to earth. A nice big M4 screw with toothed washer on the case connected directly with thick wire to the earth tag on the IEC socket is recommended. The board can then be grounded via the midi, output socket or GND pad as detailed above.

The board mounting pads are not connected to 0V.

Tony
yves
Oh, Seems like I didn't read page 18 of the builders guide thouroughly enough... Thanks for your extensive answer, Tony! And thank you for providing this great project to the community. I really love the TM3030.

Cheers,
Yves
studyman
Hello,
i want to put the pcb in a plastic case with a top in aluminium, should i connect it to a ground ? midi sleeve for exemple (i have metal midi socket)...?
Pierre
Synthbuilder
studyman wrote:
i want to put the pcb in a plastic case with a top in aluminium, should i connect it to a ground ? midi sleeve for exemple (i have metal midi socket)...?


The TM3030 will give better performance in an all metal case. However, if you do have only a metal panel then you can connect that to 0V. That is with a wire to the GND pad on the TM3030 PCB or the grounding lug on the output socket.

Tony
studyman
can i screw directly the pots in the metal panel ?
studyman
i have a little sound of "buz" at every notes played...
Synthbuilder
studyman wrote:
can i screw directly the pots in the metal panel ?


Yes. If you connect the metal panel to 0V (GND) then that can help cut down any buzzes.

The main problem with an all plastic case is 50Hz modulation of the VCO pitch. It's not a buzz as such but a dirtiness to the sound - particularly with certain notes.

Tony
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