mono/stereo switch?

[col]

What is the simplest way to implement a mono/stereo switch?

Is it just a case of summing the two channels using resistors on one side of the switch and having the other side bypass the sum?

any options on this or opinions?

cheers,
col.

 

[mickeymoose]

It depends of where in the audio chain monoize (?) the signal

 

[AndrewT]

depends on the purpose.
If you want two mono channels and don't require the stereo signal, then simply short together the two channels with a single pole switch or relay or dual FET.

If you want a mono channel for some thing and still require the stereo channels, you need a sum circuit that combines the information without cross coupling the stereo signals. An inverting opamp topology with two input resistors does this. This would typically drive a mono sub woofer.

 

[dannybeckett]

This is exactly what I need as well. Andrew could you find an example? This is what I planned

An externally hosted image should be here but it was not working when we last tested it.

 

[lauret]

Check this article on passive summing: Why Not Wye. Caveat here is the introduced crosstalk on a parallel stereo output. To get around that, use a opamp based summing amplifier.

 

[mjf]

hello.
here are two examples,one active with opamps
and the second one with a simple on/off switch (and two protection res if needed).
greets

 

[dannybeckett]

thanks for that!

 

[col]

Thanks for the replies. I'm retro-fitting an early 90's amp using a modern pre-built amp module and want to get as many of the old amp switches and functionality working as possible. I am looking at monoing the signal after the chassis input connectors before the amp module inputs. Both channels will be either stereo or mono (unbalanced).

Will try the examples given (and read the Rane note again).

cheers,
col.

 

[Joachim Gerhard]

That´is the way i do the Mono / Strereo switching in my preamp