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Grounding with separate enclosures?
Grounding with separate enclosures?
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Old 27th December 2017, 09:58 PM   #1
TheNuge is offline TheNuge  Germany
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Default Grounding with separate enclosures?

Hi!
I hope this question hasn't been answered many times before, but at least I haven't found the exact answer I was looking for...
I'm building a stereo amp, based on Thel Accusound Pro modules, where part of the power supply needs to be in a separate enclosure from the enclosure with the actual amplifier.
The power supply enclosure will contain the transformer and part of the capacitors, and the amplifier enclosure the boards and the rest of the caps.
The plan is two use two separate voltages, UB1 (approx 85V DC) and UB2 (approx 90V DC), for the amp modules, using both sets of secondaries from the transformer.
The two enclosures will be connected with Neutrik PowerCon cables, one each for UB and UB 2.
Question is, how do I ground the whole thing for safety and minimal noise?
I've drawn up a "diagram", but left out the points where the enclosures are grounded:
Click the image to open in full size.
Any advice would be very much appreciated!

Cheers
Es
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Old 28th December 2017, 10:42 AM   #2
DF96 is offline DF96  England
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For safety, connect the PSU enclosure to mains ground. Connect the amp enclosure to the PSU enclosure.

Choose one point in your audio circuit to connect the audio signal ground to an enclosure.
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Old 28th December 2017, 10:57 AM   #3
TheNuge is offline TheNuge  Germany
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Quote:
Originally Posted by DF96 View Post
For safety, connect the PSU enclosure to mains ground. Connect the amp enclosure to the PSU enclosure.

Choose one point in your audio circuit to connect the audio signal ground to an enclosure.
Thanks!
That is kind of what I was thinking - have a signal ground point in the amp enclosure, connect the PSU to mains ground, and rund a separate ground wire between the two enclosures.
I'll try putting it together like that and report back!

Cheers
Es
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Old 28th December 2017, 11:10 AM   #4
turk 182 is offline turk 182  Canada
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there seems to be a whole lot of redundant grounding going on in that diagram, as in the two supplies are grounded within the psu case and again in the amp case it and i could not see where the case common is made?
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Old 28th December 2017, 11:46 AM   #5
scottjoplin is offline scottjoplin  Wales
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Yes, there are a lot of ground loops in there, you should focus on getting rid of those. There are unnecessary loops in the capacitor banks
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Old 28th December 2017, 05:37 PM   #6
AndrewT is offline AndrewT  Scotland
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Your PSU is wired incorrectly.
You have taken the Centre tap of the secondaries to the OUTPUT of the smoothing bank.

Instead take the Centre Tap to the INPUT of the respective capacitors banks.

Once you have that, you will find that the two capacitor banks share a Zero Volts. That potentially can cause problems in downstream circuits. You must avoid LOOPs in the downstream circuitry that may be affected by interference impinging on that loop.
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Old 29th December 2017, 09:24 PM   #7
David Davenport is offline David Davenport  United States
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Audio Component Grounding and Interconnection

See section 4.3

Dave
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Old 30th December 2017, 09:42 AM   #8
TheNuge is offline TheNuge  Germany
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Thanks guys!

@ Dave Davenport: I've downloaded your doc and had a look at section 4.3, but I'm still not sure I' m on the right track... But many thanks for taking the time to write that up and share it with everyone - drinks are on me next time you're in the Stuttgart area of Germany!

I've now split the centre tap of the PT and fed the inputs of the capacitor banks. UB1+ , UB1 0, UB1- will now go through one cable, UB2+ , UB2 0, UB2- though the other. The safety ground connecting the two enclosures through a separate cable. Will that work?

Cheers
Es
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Old 30th December 2017, 10:10 AM   #9
DF96 is offline DF96  England
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You still have a ground loop, as there are two paths from the CT to the star point. Why do you have two secondaries sharing one CT connection? If the power transformer actually has two separate secondaries each with their own CT then you can build two separate PSUs each with their own centre. Then join the two at the star point.
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Old 30th December 2017, 10:52 AM   #10
AndrewT is offline AndrewT  Scotland
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Your new smoothing cap arrangement is much better.
And you have continued that "in on one side and out from the other side" as the power reaches the amplifiers.

To refine that, look at the transformer through rectifier to the Input of the smoothing caps. This is connected by a 3 wire cable. Twist these three wires to minimise loop area. That minimises interference. At the terminations the termianls and their wires must also maintain that low loop area. Do not build in big loop into current circulation cables.
Look at the output from the smoothing caps that flows to the amplifier. Again you have 3 wires. Use a twisted triplet just like the previous taking care to minimise the Loop Area in the cable and at the terminations.

Sumarising the above.
There should be NO SINGLE cables taking current from Source to Receiver. NEVER.
All current flows around loops. Every microamp that leaves a Source MUST RETURN to that Source. It's that Flow and Return pair of cables that can form LOOPS. It's your job as Builder to identify all those Loops and minimise the LOOP AREAS.

Following on from DF:
If you have one secondary that is centre tapped, then you you can use ONE PSU and that supplies both amplifiers. This will have 3 secondary tappings.
You have two seconadries each with their own centre tap and these are isolated from each other. This will have 6 secondary tappings.
There are two more alterantives:
A Dual secondary has 4 tappings and two tappings are isolated from the other two.
A quadruple secondary that has 8 tappings, each 2 tapping secondary is isolated from all the other secondaries.

Which do you have?
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Last edited by AndrewT; 30th December 2017 at 11:03 AM.
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