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I have 3 components: dual +/- power supply, linear voltage regulator, and pre-amplifier. They are to be mounted in a aluminum box. The PSU is powered by a 24V DC bench supply. I am confused on where to ground each component with regards to the "common" ground of the PSU. The pre-amp is processing signal data, where as the LVR is simply stepping +12V down to +9V.

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My first thought is to connect the PSU "common", the GND of the pre-amp, and GND of LVR to a star ground mounted on the chassis. I don't want to damage the PSU so I was hoping to get advice from more knowledgeable folks. Thank you!

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  • \$\begingroup\$ #Tristen Lee. Well the most important point is not to let the pre amp ground path crossing over the PSU or LVR 's ground path. The PSU is a tough guy, it would not be damaged the the pre amp. It would only make the pre amp noisy. \$\endgroup\$
    – tlfong01
    Mar 27, 2021 at 3:35
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    \$\begingroup\$ I always recommend this EDN article to the grounding newbies: (1) Properly ground your circuits - Ritchey & Knack, EDN 2017jan06 edn.com/properly-ground-your-circuits. Cheers. \$\endgroup\$
    – tlfong01
    Mar 27, 2021 at 3:39
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    \$\begingroup\$ Actually, bypassing or decoupling PSU is more important to pre amps. I always recommend noise ninjas the two part article by Robert Keim: (1) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - Robert Keim 2015sep21 allaboutcircuits.com/technical-articles/…. / to continue, ... \$\endgroup\$
    – tlfong01
    Mar 27, 2021 at 3:56
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    \$\begingroup\$ (2) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - Robert Keim 2015sep27 allaboutcircuits.com/technical-articles/… (3) Reducing sound noise when recording with Pi - Rpi SE raspberrypi.stackexchange.com/questions/111426/…. Cheers. \$\endgroup\$
    – tlfong01
    Mar 27, 2021 at 3:57

2 Answers 2

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In electronics, Common and Ground are the same thing and they just mean 'Reference 0V'. This is because, in an electronic circuit, most voltage measurements are made with respect to a common point in the circuit. The common point could be Vcc too, but it is more convenient to use the -ve terminal of the Power supply and call it GND or COM and make all measurements with respect to it. Do not confuse GND in electronics with 'Grounding' or 'Earthing', a thing done with electrical appliances to protect the user from a shock in the even of a fault.

You can simply connect all the GND and COM pins of various ICs together and to the -ve (0V, black terminal) of the PSU and you will be fine.

This terminology often confuses beginners. I too had pretty much the same doubt when I started building electronic circuits.

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  • \$\begingroup\$ I'm confused on what you mean by connect all the GND and COM pins together, to the -ve (0V) of the PSU. The PSU has a +12V, -12V, and COM pin. So do I use this COM pin as my star ground? Where does the chassis GND come into play? Edit: I was told my a colleague that connecting the -Vin of the power supply to my chassis could make grounding easier? \$\endgroup\$
    – earl
    Mar 27, 2021 at 18:22
  • \$\begingroup\$ No. The +12V and -12V are your power rails. The COM is your ground, or 0V reference. You need to connect all GNDs and COMs together. Some PSU don't come with a -12V or minus any volt rail, which is why is told you to connect all GNDs and COMs to the -ve terminal. But your PSU has positive and negative supply rails, so I can't ask you to connect all GNDs to the -ve terminal. Whatever has GND or COM must be connected together and to the COM of the PSU. Don't bother connecting anything to the chassis GND. It is of no use. \$\endgroup\$ Mar 28, 2021 at 8:22
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Proper grounding like star ground is done when you're worried that the ground can become noisy. This noise usually comes when there's a lot of switching action (i.e. think about the ground of a DC/DC converter).

Since in this case it seems you have an LVR and an amplifier, most of the switching noise on the ground will come from the PSU. This PSU is probably optimized to avoid that noisy ground so I would suggest connecting the GND of the amplifier and LVR to the chassis and the the COM pin of the PSU to the chassis as well. Depending of the amount of current you might want to have separate paths to the chassis (i.e. different wires) instead of shorting them all together until they reach the chassis.

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