Audio Component Grounding and Interconnection

David, this was an incredibly well-written and informative post. Thanks for taking the time to write this.

With regard to the section on using a physically separate power supply; this was not completely clear to me. Perhaps as such, you can clarify this.

My understanding, which may very well be incorrect, assumes the following:

-All of the power supply commons (negative returns) return to a single star point within the power supply, and this star is not returned to chassis ground within the power supply. Or are the power supply commons, which are connected to a star within the power supply chassis, also connected directly to the power supply chassis? This would imply two star ground returns for the power supply common; one on the power supply chassis, and the other on the amplifier chassis. This would of course create two separate grounds, with a potential difference between the two chassis, and could generate a ground loop.

-The safety ground of course connects directly to the power supply chassis.

-Or the power supply common star is only connected to the star ground within the amplifier chassis. The star ground within the amplifier chassis is connected directly to the chassis within the amplifier.

-The safety ground, which is connected directly to the power supply chassis, is also connected to the amplifier chassis.

Your guidance and clarification would be very much appreciated!

Thanks & Regards,

Bruce
 
Can a set of interconnect like this be custom made?

To be precise, I'm looking for interconnect with a (+) wire connected to both ends of the interconnect, a (-) ground wire connected to both ends of the interconnect, and a shield that is NOT connected to the (-) ground wire (as some interconnects out there) and where that shield is connected to only one end of the interconnect. Thanks.
 
I has been a while since I replied to this thread, so here goes:

In response to Bruce Berman:

Simplify. Consider the whole system to be contained in a single chassis and then partition the chassis as need be. As the chassis is partitioned, maintain continuity between the different parts of the chassis.

Another way to look at it is that all chassis are directly connected to the mains green-wire safety ground. Do not convolute safety ground(s) with power common(s) or signal common(s).

Then, at some point, it really doesn't matter where, the power common and signal common points are connected to the chassis/safety ground. This is for safety and should not be considered a path of regular current for the integrity of the signal. If designed correctly, everything should operate normally without the safety ground. The safety ground is there for protection when/if things go wrong.

Although I say "it doesn't matter where," in practice, i usually connect signal and power commons to the safety ground directly to the point where the green-wire ground enters the system.

In response to David08:

It is quite common in professional installations for cable shields to be connected on the source end only. I have not experienced a problem with shields connected on both ends for a home instillation.

It should be very easy to modify a cable to cut the shield connection on the destination end of a cable if need be.

Dave
 
How to deal with multiple PSUs within a single chassis

First to thank David for an incredibly useful article. Sorting out 0V systems in audio is not easy to do well and your article gives me confidence to tackle it!

My question for David or anyone else who can help please ...

I am designing a small rack housed analogue mixer in a 6U x 19" eurocard rack frame. There will be four modular eurocard PSUs, two for analogue audio, one for relay power and one for digital control.

Each of the PSUs has a pcb mounted IEC connector, so I will have 4 mains leads coming into the rack frame each cabling to a common mains distribution block.

I know I can create a single star point for all of the PSU commons, the audio signal reference bus and safety to chassis but I'm not sure what to do with the four earth lugs on the IEC connectors?

Should I leave all of these but one disconnected from supply ground to maintain the star configuration? Any safety concerns if I do this?

Thanks for your help with this.

Regards

Robert
 
Each IEC MUST have its earth connected.
Otherwise, should one or more not be plugged in fully for any reason, accidentally or otherwise, you would lose the safety ground.
It will cause no audible detriment.


Many old houses in the USA only have two wire outlets & for those houses the third wire ground is completely useless.. The neutral (white wire) is somewhat referenced to ground. The black wire is definitely hot.



https://inspectapedia.com/electric/Electrical_Outlet_2-Wire_Connections.php
 
Yes, however many USA home outlets are also wired backwards.

With a two wire to three wire adapter and a tester, one can check the wiring.


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With a two wire to three wire adapter and a tester, one can check the wiring.
Unfortunately, most simple testers will not detect a potentially lethal mis-wire, the reverse polarity bootleg ground (RPBG).

A bootleg ground is a wire jumper connected between the bonding screw terminal to the outlet's neutral connection. This practice is a NEC code violation, but a standard 3-lamp receptacle tester will report the outlet as correctly wired, often passing electrical inspections.

An RPBG has hot and neutral wires connected to the opposite terminals (reversed polarity) with the jumper or pigtail connection (bootleg ground) placing live voltage on all grounded parts of all equipment plugged into that outlet, thus allowing people to come into contact with a deadly voltage with a current path back that will not trip a normal circuit breaker, or a GFCI.

Further information on the RPBG can be found here:

Failures in Outlet Testing Exposed | EC&M

A non-contact voltage tester (NCVT) can be used to detect RPBG outlets.
 
This thread is one of many that I used when "trying" to understand the best way to to stop my double insulated (no requirement for electric safety earth) components giving me static shocks!....(The measured potential difference was within the allowed limited for Double insulated).

I might have to revisit what I did & modify, but for now it works....Basically thick cable of suitable voltage/current capacity) soldered to eye terminal sandwiched between the join of the back panel & side panel where there is a screw, as bare metal in the join. This on all three items (network player, amp, CD). The CD & network player connect to the connection on the amp. The amp connection goes to an insulated block with a class x/y cap & a resistor in parallel. This then goes to the earth pin in a plug which is plugged into the mains filter block as per a normal plug.

This now keeps the whole casework at the same potential as earth therefore its no longer "floating" & cannot give off static shocks!

Where I am the electrical safety earth is actually the neutral & actually the armour as we are on PME & single core incomer cable to the fuesboard. Then off course all gas pipes, water pipes & metal sinks & taps are connected to the earth connection in the fuse board to x-bond as per the regs.

I still think I need to add a bridge rectifier maybe next to the cap & resistor?? I also still think that a couple of the back panel connections on the network player are purposely connected to the casework as outputs.....need to have another detailed look...!!!
 
My SE amp (L' Amp - L’Amp: A Simple SIT Amp: Part 1 - diyAudio) was done with star-grounding. Transformer has 2 secondaries, so I've built 2 PSU (1 for left and 1 for right). Their ground go to star. RCA shield from each channel input and its bias ground go to local references (source of FET).
- With inputs shorted, the amp is super silent (mute).
- With open inputs, almost mute.
- With RCA cable + open ends, almost mute.
- With RCA cable + 2k resistor in each end, mute.
- If the resistors at RCA end (left and right) share the same "ground", audible hum is generated. This occurs with any source connected to the amp (CD player, DAC, etc) because their RCA shields are connected to ground.

Where is my error?

Obs.: I tried loop breaker to star point, earth to star, no earth, all without success.

I know, I'm replying to a 5 year old post but since I had to deal with almost the same problem just the other day, I'll leave a comment here and maybe that is helpful to someone at some point...

In the "not OK" case, where the RCA cable's ground is connected together at the far (source) end, a loop is formed by the two shields as these are both connected to CG in the amp. Now for example, if there is a varying magnetic field from a transformer, it will induce a voltage into that loop and a current can flow and depending on how the inputs are hooked up in the amp, that can represent a voltage drop over the amps input resistance which gets amplified.
What helped in my case:
- Ensure input jacks shield's are insulated from the chassis
- Connect the input jack's shields together on the inside
- have a single connection from there right to your star-ground

What also helps:
- Using an interconnect that uses a single lead for ground (no loop is formed but your choice of off-the-shelf cables become much constrained)
- Using an insulating transformer at the amp's input (but then you have another element in the signal path that could potentially degrade audio quality)