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Author Topic: Balanced to unbalanced wiring  (Read 16171 times)

Sin x/x

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Re: Balanced to unbalanced wiring
« Reply #15 on: August 06, 2006, 02:26:12 AM »

Tom C wrote on Fri, 04 August 2006 15:44

Sin x/x wrote on Wed, 02 August 2006 16:47


Properly balanced equipment has the shield connected to chassis ground. This way earth currents and RF interference can't influence the audio signal. And this is the best way to connect equipment.



Just out of curiosity, in most parts of Europe we have an electrical system with 3 connectors: hot, signal ground and earth (ground).
That makes proper cabling very easy (at least if no dumb-ass has connected signal ground and earth somewhere in the house and you have to find out where. In my sisters house it took me half a day to find out and re-cable properly...).

Do you guys on the other side of the big pond have the same?




Most manufacturers connect their equipment, just like you said, wrong. (With a signal earth, and this causes the "pin 1 problem)
This is actually an unbalanced connection, what Mr Lavry also later correctly  said.
This can of cause never be the best way to connect equipment. Because this way, earth currents and RF interference will influence the audio signal.

What you need for properly balanced operation is: a positive signal, a negative signal and chassis earth.

This means, in 90% of the time, you have to get a soldering iron and correct the manufacturers "mistake". This takes 5 minutes

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Sin x/x

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Re: Balanced to unbalanced wiring
« Reply #16 on: August 06, 2006, 02:36:29 AM »

Bob Olhsson wrote on Sat, 05 August 2006 12:21


It would be nice if there were interface standards but there aren't and even where there are, many popular manufacturers have chosen to "cheap out" rather than provide a high quality, bullet-proof interface.

There is a bulletproof interface: Balanced with chassis earth, but only a few manufactures actually use this.

Bob Olhsson wrote on Sat, 05 August 2006 12:21


Dan's approach is just about the wisest I can think of.


I have to disagree.

Unbalanced connections always causes extra noise.

The only good solution is to create a properly balanced connection.

Edit: useless info removed.

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Sam Lord

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Re: Balanced to unbalanced wiring
« Reply #17 on: August 12, 2006, 11:43:19 PM »

In our all-unbalanced designs, we always separated earth/chassis ground from signal ground.  Power supplies always had at least 2 secondaries on toroids to extract a center tap as the signal ground reference.  Our noise was extremely low, even though cable shields were connected to (admittedly very-low-Z) signal ground.  I expect that the same practice would be good for balanced gear, where signal ground inside chassis would be separate from the ultra-low impedance web of connected earth (single-point), chassis, and wire shields.  However, I've read good safety arguments for a single-point connection of signal ground to earth ground at the quietest spot, like the facility's true AC ground point.  Comments?  Am I too far off topic? (Then please ignore...)  Thanks.
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Sin x/x

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Re: Balanced to unbalanced wiring
« Reply #18 on: August 13, 2006, 08:50:16 AM »

Sam Lord wrote on Sat, 12 August 2006 22:43

In our all-unbalanced designs, we always separated earth/chassis ground from signal ground.  Power supplies always had at least 2 secondaries on toroids to extract a center tap as the signal ground reference.  Our noise was extremely low, even though cable shields were connected to (admittedly very-low-Z) signal ground.  I expect that the same practice would be good for balanced gear, where signal ground inside chassis would be separate from the ultra-low impedance web of connected earth (single-point), chassis, and wire shields.  However, I've read good safety arguments for a single-point connection of signal ground to earth ground at the quietest spot, like the facility's true AC ground point.  Comments?  Am I too far off topic? (Then please ignore...)  Thanks.


With balanced systems chassis earth and signal earth should be connected.
Because there is electrostatic coupling between chassis and the internal circuits, noise on the chassis can  influence the audio signals. If you connect chassis ground to signal ground, the 0 volt reference (signal ground) fluctuates with the chassis noise and so the audio signal is virtually noise free.

It is essential that chassis earth and signal earth are connected only at 1 place. If there are more connections, noise will interfere with the audio.
Of cause signal earth can be split further into digital and analog earth etc... But they should only be connected at 1 point. This is known as the star grounding scheme.
There are 3 locations for connecting chassis and signal earth.
1 At the power supply output.
2 Between the power supply capacitors.
3 At the cable input where the cable shield is connected to the chassis.
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Sam Lord

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Re: Balanced to unbalanced wiring
« Reply #19 on: August 13, 2006, 10:35:43 PM »

Sinx/x--thanks, a star was the idea. I appreciate your explanations here, most sensible.  I need to look at how the secondaries should be done in a balanced system (differently!), very OT here.  Sam
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