Use transitor as a switch to ground audio input

Question

I have got a probably very dumb question. I was not able to find an answer on the other topics because they always described the use of transistor as a switch for other applications.

I have a circuit with audio signal passing through and going to a speaker. I would like this signal to be grounded unless a 5V TTL signal is on. In this case this will have to go to the speaker. Can I do it with a transistor?

All the example that I found are about something (like a LED) already connected to a a voltage and then with the transistor either grounding its cathode or not and I do not know whether this would work in the other direction (what I would like to do).

Can I use a transitor to ground/mute the audio signal when TTL signal is zero?

Answer 1

If what you want is the ability to switch between audio and silence, you can use an analog mux to switch between your audio input and ground, instead of the amplifier output. As an example, you would ground S1, S2, and A1, hook up your low power audio source to A0, connect A to your amplifier, and use S0 as your switch input.

If you want stereo, you'll need to use a chip that has two analog multiplexers, and repeat for each line.

Answer 2

I have a circuit with audio signal passing through and going to a speaker. I would like this signal to be grounded unless a 5V TTL signal is on. In this case this will have to go to the speaker. Can I do it with a transistor?

The easiest cheapest option is to use a 5 volt electromagnetic relay. It has a switch contact operated magnetically by a coil driven electrically. Like one of these: -

Pins 2 and 5 are the coil and pins 1, 3 and 4 is a changeover contact.

You might need to consider using a transistor to buffer the coil from the TTL signal because the coil current can be as high as 100 mA. Use this: -

Take care not to ground the amplifier output in case it gets damaged. Instead open circuit the speaker.