audiogroundingpower supplysound
I recently took apart a Mackie 220W power supply for an analog sound board. Much to my surprise I found the following scheme:
Earth grounded:
48V
-18V
18V
Seperate, isolated ground:
12V
5V
I am not sure if this has something to do with it being a supply for a sound board, but why would there be 2 isolated grounds?
If your PSU looks like this 12 Volt (single voltage output), 30 amp power supply:
adj label probably refers to an adjustment screw, not to any of the terminals.-V label does not mean -12V, it is equivalent to COM on the PSU in your reprap link. ⏚ terminal to have a low resistance to the +V terminal with all cables disconnected.I've had the same constraints and had to find the solution that others are talking about. I don't know what capture speed you want or what sensors you have but there is almost an integrated solution using TI's chipsets like this: -
This is a generalistic circuit suitable for multiple options but you can get more bespoke variants of the same theme suitable for the individual sensor types. The solution that I ended up using was with ADI because it was self-powered thru the isolation device: -
(source: analog.com)
The ADuM5401 has a small DC-DC converter internal to the device that can provide enough power for the front end AD7793 chip. You might also consider the good-old isolating amplifier: -
For less problematic ground potentials you can even use the LTC1043 isolating capacitor thus: -
Best Answer
First we need to realize that this power supply for a large format mixing console, probably with about 40 channels, and 16 mix buses. As a result, there is a need for multiple supply rails. This breakdown may not be exact for the console that goes with the power supply, but in general:
The +/-18V rails need to be earth referenced by convention, otherwise ground loops will be a problem when the console is interfaced with other equipment downstream. The 48V bus also interfaces directly with audio circuitry, so must be referenced to the same ground. The 12V and 5V buses are powering electrically noisy things. To keep that noise out of the audio signals, they need to be kept isolated from the audio ground.