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Basic Layout/Wiring Question re: Outboard PSU
Basic Layout/Wiring Question re: Outboard PSU
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Old 18th June 2019, 11:18 AM   #11
ctrlx is offline ctrlx  United Kingdom
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the psu 0v should be connected to the chassis, as shown below.
in the 2nd box, make another connection to chassis from the incoming psu 0VClick the image to open in full size.
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Old 18th June 2019, 04:14 PM   #12
rongon is offline rongon  United States
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Basic Layout/Wiring Question re: Outboard PSU
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Originally Posted by ctrlx View Post
the psu 0v should be connected to the chassis, as shown below.
in the 2nd box, make another connection to chassis from the incoming psu 0VClick the image to open in full size.
Yes, but in the 2nd box (audio chassis) exactly where is the best place to connect 0V to chassis? At the input jacks? Or at the socket where the umbilical plugs in?
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Old 18th June 2019, 06:30 PM   #13
ctrlx is offline ctrlx  United Kingdom
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Quote:
Originally Posted by rongon View Post
at the socket where the umbilical plugs in
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Old 18th June 2019, 07:08 PM   #14
rongon is offline rongon  United States
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Basic Layout/Wiring Question re: Outboard PSU
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at the socket where the umbilical plugs in
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Old 19th June 2019, 12:18 PM   #15
ctrlx is offline ctrlx  United Kingdom
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yep, thats it.
the alternative it to use 4 wires in the umbilical, with the 4th solely to connect the two cases.
using either method, the way the safety aspect is addressed.
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Old 19th June 2019, 01:15 PM   #16
rongon is offline rongon  United States
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Basic Layout/Wiring Question re: Outboard PSU
Thanks. But, now that the signal ground (0V) is directly connected to the chassis at two different locations--one at the PSU chassis AC inlet and power transformer center tap, the other at the audio chassis umbilical inlet--won't the likelihood of a ground loop problem be increased? At this point, I'm asking that as a learning opportunity, because...

It looks like the 4-wire approach is the only realistic way to proceed. Keep the safety ground separate from the signal ground, so I don't end up with ground loops. Hopefully the attached drawing shows a good grounding scheme.

- The signal ground is connected to chassis at the audio inputs *only*.

The safety ground connects at two places, one for each metal chassis, with a wire connecting the two, ultimately connecting both metal chassis directly to the ground lug on the AC plug.
- In the PSU chassis, the safety ground connects to a post in the chassis located right next to the AC mains inlet.
- In the audio chassis, the safety ground connects to a post in the chassis located right next to the umbilical inlet socket.

The basic idea is that the audio circuits have the shortest, lowest impedance path to the chassis, while the high current loop of the rectifier bridge/reservoir caps has a longer, higher impedance path to the chassis.

The safety ground merely connects both chassis to the mains earth (green wire from AC plug here in the US) to short the chassis to earth in case of an accidental short of DC voltages to the chassis. That short causes excess current to flow across the mains fuse and causes it to go open, cutting off AC.

I think that's right.
--
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Last edited by rongon; 19th June 2019 at 01:42 PM.
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Old 19th June 2019, 10:21 PM   #17
MAAC0 is offline MAAC0  Portugal
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I would use a 4 pin or even 6 pin connector since it's different from 3 pin XLR (audio) and 5 pin (DMX). On my small Behringer mixers which had plastic "mouse" connectors I have fitted those small 3 pin Threaded "Aviation plugs" when the original pins broke.
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