Using CMOS switching instead of a 3PDT?

Started by spargo, April 17, 2011, 05:16:56 PM

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spargo

Basic idea: It's an XLR momentary A/B box.

The input is split into two outputs (A and B).  To control which channel is active (only one at a time should pass a signal), a DPDT is used to alternate shorting pins 2 and 3 on either output A or output B.  Shorting the pins effectively mutes that channel.  Does that make sense?

spargo

I'm still at a loss for this.  Stuck on the CD4053, I tried a simple switching system using a J201 JFET.  I was using this as an example: http://brunningsoftware.co.uk/FET.htm

Same problem as the CD4053 - there seems to be some resistance and the signals are not fully muted.  But even worse the J201 also had ridiculous pops during switching.

spargo

I'm now also looking into the possibility of using something related to the millenium 2 bypass.

A basic DPDT switch has two poles, each of which can be thrown in two directions.  I only need one direction from each of those poles (basically a two pole, single throw switch for the actual switching), leaving me with two of the six switch lugs empty.  Somehow I need one of these to apply voltage to the JFET to close the switch and turn on/off an LED.

In the Millenium 2 bypass diagram: http://www.geofex.com/article_folders/millenium/millen.htm I would assume that the path going to "internal DC resistance to ground" applies some sort of voltage to flip the transistor's gate.  Any idea how to do this in a microphone application?  Only way I can think of would involve connecting +9V to one of the two mic terminals (hot or cold) when the switch is not active and I'm not sure what kind of issues this would introduce, especially with phantom power involved.

spargo

I've been stuck on this for a month.  Any suggestions?  The JFET and CD4053 switching had resistance in the signal and did not fully mute the boxes.