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I want to replace my mechanical A/B switch (lots of pops and clicks) for my headphone/speaker on my PC and I was looking into the CD4066 (cmos quad bilateral switch). I look at a lot of design and I see many using input coupling capacitors with resistors divider to manage the +/- audio signal coming in. But I found this approach bringing more components then required. I layout this schema on my breadboard, took a look at my scope and everything seems fine. The thing is to bring the reference ground of the source midway with a simple resistor divider. No DC offset to manage! Do I miss something here?

PS.: The 6.5 V source is arbitrary, this is the value of a power supply I found in my junk bin. But this fit the build for a 2 Vp-p audio input source with some room to spare.

PS2.: The D Flip-Flop is for a smooth transition between the outputs and bypass capacitors not draw for clarity.

A/B E-Switch

winny
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Steve S.
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    Since you ask if you are missing anything, there is no strong ground reference between audio and power supply, as the resistor divider only works at DC, and this requires that the power supply output is floating instead of ground referenced. And if you intend to drive headphones with this, I don't think you have realized that the CD4066 can work with maximum of around 1mA current and it basically is few hundred ohms of non-linear resistance in series with the signal, so it is rather poor if you have typical headphones with few tens of ohms of impedance. – Justme Sep 24 '22 at 07:21
  • How about MAX14778 or similar? – rkosegi Sep 24 '22 at 13:52

2 Answers2

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As @Jonk pointed out in his comment, switches load must be "high".

Here is a schematic that works, but note also that "feedthrough" is "high" because of the parasitic capacitors.

When switch is "closed" ...

enter image description here

When switch is "open" ...

enter image description here

Generally, CD4066 switches are used twice, one serial and one parallel.
Reducing this effect (200 uV -> 4 uV).
Note also that a "power" op-amp would be needed after ...

enter image description here

Antonio51
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CD4066 has an internal resistance of over 100 ohms, that will destroy the performance. unless your headphones are very sensitive.

I would be looking for a better multiplexer chip and considering going with discrete MOSFETS instead of an IC

I would also consider doing it all in someone elses software by fitting the switch into the presence detect line of the PCs front audio header. flip the switch and the pc will think you pulled the headphones and switch the audio the the rear outputs

On the other hand you could just buy an audio mixer that has has headphone/loudspeker switch.

Jasen Слава Україні
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