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Basic channel selector request

Basic channel selector request

Basic channel selector request

I'd like to toggle between two sources of stereo audio (each having L, R and Neutral). Who can help ?

I'd also like to do that using one of those basic bistable on/off switches

- And more important, if possible: basic components only. No extra ICs apart from OpAmps, Schmitts and drivers that I happen to have laying around this time.
I not only don't have ICs at hand: they tend to degrade the quality of the signal if I don't buy the right one.
- I have not negative supplies, in case OpAmps be suggested
- Part count is not so important
- If transistors are required, BJTs are preferred
- I'd like to avoid relays too, although they will be my choice if none of the brilliant minds don't find an option that fits the criteria above

Thank you ahead for your time

RE: Basic channel selector request

What voltage levels are involved? If one or two V peak, I would try a series resistor, say i kohm, in each channel to start with. would then use FET transistors from resistor to groound. And then Control each FET from collector of TR1 and TR2. The FET with Gate high will then short signal to ground and the other one will be HiZ and let the signal through. BJT:s are not as symmetric as FET:s are. FET:s can short out negative signals as well as positive ones.

With an extra 1 kohm, you will lose some high-pitch if you have long cables. One nF (around 10 m Cable) will give you 3 dB down at around 160 kHz, so it isn't so bad, after all. So, you may go to 4,7 or 5,6 kohms, that will improve on/off ratio. Just try and see what gives you the best result.

For better solutions, there are lots of other ways of doing it. Relays with gold flash Contacts is what I would use. No extra damping, no non-linearity and absolutely no distortion.

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Basic channel selector request

Google "Analog Crosspoint IC"... something like the ADG2188 and its ilk is probably what you're after.

Dan - Owner

RE: Basic channel selector request

Thank you MacGyver
A specific chip like that is my dream, but far out of reach right now. Hardly accessible/findable in my country.

Now, Skogsgurra's solution seems the ideal solution for the moment, but I have a question about this arrange:

Won't muting a source (grounding it) also mute the other ?

Both sources go to the same amplifier in the end

I've attached a sketch of the propposed circuit. See if it's understandable, and if it represents what you pictured. Please suggest corrections, if required.
Don't mind the astable part

RE: Basic channel selector request

Yes, you need resistors, too. See Picture:

May have been too quick, you lose more than 3 dB. But this is the simplest way - with the resrtictions given. If you make the T assymmetric, with 1 k in and 4.7 k to amplifier, you lose a lot less than 3 dB. The BS170 has around 2 ohms channel resistance when on. So isolation will be adequate even with 1 k in. Something like -63 dB. I think.

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Basic channel selector request

Make that -57 dB, duh. Still acceptable, I think.

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Basic channel selector request

A bistable relay would solve everything in the simplest manner.

RE: Basic channel selector request

Relay it is, then
The volume that comes from the devices are already low IMO, cannot lower it more.

I was thinking about economy and lifespan, but no problem: The relay will stay the very most of the time in one position anyway

Good to know about this FET to ground option. Learned a lot.
Thank you all for the help

RE: Basic channel selector request

Wouldn't we all? But that was excluded by the OP: "I'd like to avoid relays"

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Basic channel selector request

I'd use a switch. DPDT. If you want it to be a toggle (push to change), then use a latching push button.

If remote, then a relay as discussed.

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