So I've been DIYing and I'm wondering, is it ok to keep ground wires from different signals connected?
For example #1 I'm making a simple XLR A/B box, and I'm not sure if I need a three pole switch or if I can use two and keep ground wires from both inputs connected to the output.
#2 I have two TRS inputs and 2 TRS outputs, and I'm gonna use a switch to split sides or keep them stereo. If the switch is on, TRS output #1 will only out merged L sides from both inputs, and #2 merged R sides, and when the switch is off, both stereo signals should just pass through. It's the same situation, do I need a triple pole switch, with the 3rd pole being used to disconnect grounds while not splitting sides, or is it ok to keep them connected at all times?
For example #1 I'm making a simple XLR A/B box, and I'm not sure if I need a three pole switch or if I can use two and keep ground wires from both inputs connected to the output.
#2 I have two TRS inputs and 2 TRS outputs, and I'm gonna use a switch to split sides or keep them stereo. If the switch is on, TRS output #1 will only out merged L sides from both inputs, and #2 merged R sides, and when the switch is off, both stereo signals should just pass through. It's the same situation, do I need a triple pole switch, with the 3rd pole being used to disconnect grounds while not splitting sides, or is it ok to keep them connected at all times?
No need for switching grounds. Ground is 'without signal' so switching grounds is switching nothing.
With symmetrical/balanced (pro) XLR, both hot & cold (pin 2 & 3) should be switched as both carry signals.
XLR pin 1 is, again, nonswitched ground.
With symmetrical/balanced (pro) XLR, both hot & cold (pin 2 & 3) should be switched as both carry signals.
XLR pin 1 is, again, nonswitched ground.
Switching grounds for consumer audio equipment inputs is considered by some people to be controversial. Ground often carries noise that can adversely affect equipment operation. However, switching grounds can result in arcing of switch contacts from switching ground loop currents. As a result switches or relays may have limited life in that application.
Also, you might try searching for the word 'grainy' in the attached document on grounding. Such problems are one reason some people would like to switch audio input grounds.
Moreover, in the IEEE book, "Grounds for Grounding," there is a section on ,"Grounding-Related Myths, Misconceptions, and Misapprehensions."
In that section there is a set of bullet points as follows:
*There is nothing magical about “ground”;
*Ground is simply a path for flow of return current.
*The term “ground” is relative and is too ambiguous!
*To avoid confusion, avoid usage of the generic term “ground,” unless utilized in conjunction with some descriptive term or adjective.
*Ground is a very convenient fantasy invented by engineers to simplify life but, like other fantasies, does not exist in reality.
*Ground is not a current sink. Current flowing in a circuit must return (somehow) to its source. This seemingly fundamental concept is often overlooked, bringing about EMI problems.
*Myths, misconceptions, and misapprehension of grounding theory, units, and quantities are inherent in the integration of sensitive electronic equipment into a facility or platform. A common terminology for the concepts of power and frequency is mandatory for achieving a successful and effective design.
Also, you might try searching for the word 'grainy' in the attached document on grounding. Such problems are one reason some people would like to switch audio input grounds.
Moreover, in the IEEE book, "Grounds for Grounding," there is a section on ,"Grounding-Related Myths, Misconceptions, and Misapprehensions."
In that section there is a set of bullet points as follows:
*There is nothing magical about “ground”;
*Ground is simply a path for flow of return current.
*The term “ground” is relative and is too ambiguous!
*To avoid confusion, avoid usage of the generic term “ground,” unless utilized in conjunction with some descriptive term or adjective.
*Ground is a very convenient fantasy invented by engineers to simplify life but, like other fantasies, does not exist in reality.
*Ground is not a current sink. Current flowing in a circuit must return (somehow) to its source. This seemingly fundamental concept is often overlooked, bringing about EMI problems.
*Myths, misconceptions, and misapprehension of grounding theory, units, and quantities are inherent in the integration of sensitive electronic equipment into a facility or platform. A common terminology for the concepts of power and frequency is mandatory for achieving a successful and effective design.
Absolutely true. And the rest too.
I guess the OP's question is somewhat in between here. For practical use, switching ground (the 'convenient sink') is overdone.
But it is indeed a 'return path', for current, and the rest mentioned.
How much, and in what degree, does it apply to audio - frequenties / currents / &c?
Some twenty years ago I wrote a letter about this issue for students working with fundamental physics research, all balanced microvolt signals in cryostats (Yes, hydrogen is a metal!), to get the measurments clean and reliable. Not suitable for nonpros alas.
As it turns out RFI/EMI on grounds is a well known problem that can affect audio. A lot of it has to do with the fact that forward biased semiconductor junctions can act as small signal modulators/demodulators. As a result audio signals can become intermodulated with EMI/RFI noise. Because the noise is constantly changing it tends to show up on typical audio amplitude spectrum or power spectral measurements as noise, either as noise floor or as spectral line skirts (depending on the degree of correlation with the audio signal).
For most consumer level gear it often doesn't have much audible effect. The sound is already not that great for a variety of reasons.
As users become more sophisticated and demanding of better sound quality, pretty much any imperfection in system performance can become audible on a sufficiently good system. Here we are using electrostatic speakers, dual mono-block power amps, optical phono (DS Audio), custom discrete dacs and amplification. It turns out that every little ground loop or ground coupling problem affects audible performance. I have to spend too much time chasing down those things.
Unfortunately in today's world of wi-fi, cordless phones, cell phones, bluetooth, etc., we are awash in household environmental EMI/RFI. Even worse for me as I am on top of a hill that overlooks Sacramento Valley in California. There is a huge amount of RFI coming from that direction as is easily seen on an RF spectrum analyzer.
BTW, spent time years ago accelerating negative hydrogen isotope ions. It was fun and profitable 🙂 Not much to do with audio grounding though.
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Grounding is seemingly one of the least understood aspects of electrical circuits by almost everyone! Yes, I include myself here in spite of the fact that I worked with grounding related issues in the telecommunication industry. In short, I found that the more people involved with a grounding issue (especially the elevated/educated experts), the farther away from truth for the given problem we got.
Because we worked in a very dense EMI environment, more applied to caution than might have been needed. Having said that, it would be best to know the actual situation given by the actual audio system first before assuming the best caution.
Because we worked in a very dense EMI environment, more applied to caution than might have been needed. Having said that, it would be best to know the actual situation given by the actual audio system first before assuming the best caution.