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Grounding with separate enclosures?
Grounding with separate enclosures?
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Old 30th December 2017, 11:00 AM   #11
scottjoplin is offline scottjoplin  Wales
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Is the star ground necessary in the remote amp enclosure? So long as there is a safety earth connection to the power supply enclosure I'd make the "ground" to chassis connection there
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Old 30th December 2017, 11:18 AM   #12
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by scottjoplin View Post
Is the star ground necessary in the remote amp enclosure? So long as there is a safety earth connection to the power supply enclosure I'd make the "ground" to chassis connection there
The Protective Earth wire gets connected to the mains Chassis/Enclosure.
That is a SAFETY connection and has absolutely nothing to do with obtaining a good working audio system.
There is a second rule:
All exposed conductive parts should be connected to the Protected Chassis/Enclosure.
Again this has nothing to do with obtaining good quality audio. It is purely SAFETY.

However, both the PE connection and the extra "All exposed parts" connection can give an additional route for interference reaching the audio circuitry.
Scott has mentioned
Quote:
the "ground" to chassis connection there
This is the Safety connection and the only time it ever passes any significant current is when there is a Mains Fault. This means that as Scott has suggested that it does NOT need to be in the amplifier. I tend to agree that the better location is at the PSU Zero Volts. This gives a shorter route for the Mains FAULT Current to escape to the Protective Earth. It's the Low Impedance of this route that allows the Mains Fuse to rupture quickly when there is a catastrophic failure of the Isolation between Mains and Audio.
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Old 30th December 2017, 01:54 PM   #13
TheNuge is offline TheNuge  Germany
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Hi again,
Were would I be without you guys!?!
The PT I have is this one:
Click the image to open in full size.

It's only got one centre tap, but two sets of tappings. Will that even work for generating 2 different voltage supplies?
I could also try simplifying matters by just using the 64V tapping for UB1 and completely ignoring the option of the secondary voltage for UB2.
If I do that, I'd have +64V, "0V" and -64V going through a triplet cable between the two enclosures. Can I then run the safety ground as a separate cable between the two enclosures?
Cheers
Es
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Old 30th December 2017, 02:25 PM   #14
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by TheNuge View Post
I could also try simplifying matters by just using the 64V tapping for UB1 and completely ignoring the option of the secondary voltage for UB2.
Probably not, you'd have to check that the output stage could run at the higher voltage. You could safely use the lower tapping for both the VAS and output stage, but this would restrict the maximum output. It may also be that the higher voltage winding cannot supply the necessary current for the output stage
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Old 30th December 2017, 04:45 PM   #15
DF96 is offline DF96  England
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OK. One secondary with one CT means one '0V' line in the PSU and one '0V' wire between enclosures. You can still have two bridges and two lots of reservoir caps, but you need to be careful how you arrange them so ground currents (especially charging pulses) do not infect DC.

Quote:
Originally Posted by scottjoplin
Is the star ground necessary in the remote amp enclosure? So long as there is a safety earth connection to the power supply enclosure I'd make the "ground" to chassis connection there
You seem to be conflating two quite different concepts:
1. the audio star ground, which is the reference point for signal voltages
2. the connection between the star ground and the chassis, which is for safety purposes.
Perhaps you think, as many seem to, that the star ground must be physically mounted on the chassis and so concepts 1 and 2 become physically one component thus mixing up signal currents and fault currents.
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Old 30th December 2017, 04:48 PM   #16
Mark Whitney is offline Mark Whitney  Netherlands
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TheNuge, firsts you make a schematic then the layout. Here is a beginning of a schematic (some diodes missing). It will give you a better idea of how you should do your layout.

I used Tinycad to draw the schematic. It is free.
Attached Images
File Type: png tCad1PSU.png (17.1 KB, 86 views)
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Old 30th December 2017, 04:57 PM   #17
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by DF96 View Post
You seem to be conflating two quite different concepts:
1. the audio star ground, which is the reference point for signal voltages
2. the connection between the star ground and the chassis, which is for safety purposes.
Perhaps you think, as many seem to, that the star ground must be physically mounted on the chassis and so concepts 1 and 2 become physically one component thus mixing up signal currents and fault currents.
Appearances can be deceptive, I asked a question and then answered it. The star I was referring to was the one he shows in the amp enclosure, there is no need for it to be there.
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Old 30th December 2017, 06:37 PM   #18
ICG is offline ICG  Germany
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Powercon does not provide any shielding. That way the amp is vulnerable to radio interference, it will go haywire if a cell phone etc comes close to it. Use inductors/chokes and ceramic capacitors to minimize the interferences.
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Old 30th December 2017, 06:46 PM   #19
scottjoplin is offline scottjoplin  Wales
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I'm presuming the amp case is metal, that will provide shielding, what has the Powercon got to do with it?
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Old 30th December 2017, 07:36 PM   #20
ICG is offline ICG  Germany
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Quote:
Originally Posted by scottjoplin View Post
I'm presuming the amp case is metal, that will provide shielding, what has the Powercon got to do with it?
He said he's using two separate enclosures. And he also said he's connecting the 2 enclosures with powercon. Besides the possible confusion of the amp getting an actual 220v powercon plugged into it, I'd also suggest fuses, in both enclosures.

Edit: Just in case it wasn't clear: A metal case does not protect from getting radio interference over the antenna.. er, power wires into it.
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