Speakers pop when switching A/B

rubbadubbadoo

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Apr 1, 2014
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I use my computer as a DAW (digital audio workstation) and all other tasks. After a month of having to unplug my speakers from the audio interface to the computer I decided to build a passive balanced left/right A/B switch. (These switches are non existent online). The switch works well and saves me the trouble of having to reroute outputs manually. However there is a noticeable 'pop' when I switch input from computer to external audio card and vice-versa.
I have been unable to find any schematic or advice on how to eliminate this popping sound. I have read that a 100k resistor can be used but I can find no information on where in the circuit to put it.
 

makkem

Distinguished
Hi
The normal way to switch audio in your situation would be to use a rotary make before break switch,ie it connects before disconnecting this stops the switching noise as there is no break in the audio stream.
you would need a 6p 2 way to achieve this.
The noise is a ground loop caused by connecting the grounds together.
 

makkem

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Hi
Might I ask what type of switch you are using,specifically is it make before break or break before make.
In audio switching it is usual to use make before break as it is normally the quietest in operation.
 

rubbadubbadoo

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Apr 1, 2014
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I am using a pair of 3PDT switches. One for each balanced channel, left/right respectively. Not sure I follow what you mean by 'make before break'. But if it helps, here are some more details. Input A is from my computers mini TRS to a pair of 1/4" TR. Input B is a pair of balanced TRS from my Line6 UX8 audio interface. Output is routed to a pair of powered, balanced reference monitors. The switches I am using can be found here: http://www.parts-express.com/3pdt-mini-toggle-switch--060-520
 

rubbadubbadoo

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Apr 1, 2014
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In addition, I realize the pop is coming from the voltage differences between the grounds of the two input devices(CPU/Audio Interface). Originally I had all the grounds tied together. There was no popping when switching then, however that caused a subtle yet extremely annoying high pitched ringing sound when the interface was powered on.
 

makkem

Distinguished
Hi
The normal way to switch audio in your situation would be to use a rotary make before break switch,ie it connects before disconnecting this stops the switching noise as there is no break in the audio stream.
you would need a 6p 2 way to achieve this.
The noise is a ground loop caused by connecting the grounds together.
 

rubbadubbadoo

Estimable
Apr 1, 2014
7
0
4,510
0


 

rubbadubbadoo

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Apr 1, 2014
7
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4,510
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Thank you makkem, I looked at 6PDT rotary switches when I started this project. I found the $75-$80.00 price tag to be obscene. That is over 10x more than I am willing to spend. I was hoping for a simple economical solution. Perhaps by bridging with components or by simultaneously terminating one input while switching to the other?
 

rubbadubbadoo

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Apr 1, 2014
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How on earth did you find that? I scoured Ebay and google until my eyeballs started bleeding and couldn't find one of those. I have placed an order. I will post again after installation. Thanks again!
 

rubbadubbadoo

Estimable
Apr 1, 2014
7
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Sadly the rotary (make before break) switch had no effect on the popping. After several experiments I came up with a better way to wire it. It can now be used with any 6PDT switch. Instead of tying all the grounds together I separated them left/right. In other words the ground for Input A left, Input B Left and Output Left are all tied together. The same true for the Right Input A/B/Output Right. There is no popping when switching and no high pitched feedback loop. I am a happy geek now. TY Makkem for your replies.
 
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