Switching RCA audio with a relay

Hardware
1

I’m looking for a way to use HA to switch between two audio RCA inputs. I found an automatic switcher, but the reviews concern me, so I figured HA can do it. One input will be a (dumb) TV and the other will be a Chromecast device, via an HDMI > RCA audio extractor. So, I can use the Chromecast state to trigger a relay. I’m hoping I can use an ESP8266 device tied to a 4ch relay like this. The RCA has a L+, L-, R+, and R-, so my thought is to use each channel of the relay to control each of those 4 wires. The output could attach to the middle common terminal, on input on the NC side and one on the NO side.

Something like this

relay
relay1000×1000 180 KB

Does anyone have any thoughts on if this will work? It seems like it would, but I wonder if it will cause “noise” in the signal. Is there a better way to do this?

1 Like
2

Hey, considering doing the exact same thing. How did it work out for you?

3

I haven’t had the opportunity to try it yet

4

I had the chance to try this tonight and am happy to report that it appears to work well. The audio sounded as clear as it does without the relay in the middle.

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2 Likes
5

Thinking about a manual switcher I had a long time ago, it only switched the signals and all the earth’s were permanently connected, this would mean only needing 2 relays for a stereo pair.

6

Interesting. I’ll try that configuration and see if it works.

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Did you test it? Is it possible to connect all earth’s?

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Yep, it’s tested and in use. Works great!

I connected the negatives for the connections on each relay. For example if you have left input 1, left input 2, left output all those negatives are connected together. Then right input 1, right input 2 and right output have their negatives connected to each other but not the left connections.

1 Like
9

Hello,

I know this is an old topic, but I saw that you were active on a similar post recently.
i really like what you did here. I have a few questions tho, and was hoping if you could help me out with.

Is this the setup you currently have?

Screenshot 2025-01-10 at 17.36.24
Screenshot 2025-01-10 at 17.36.241521×964 137 KB

Where the negative wires don’t even go to the relay, but connect all to the speaker.

Also, it isn’t clear to me, does this relayboard switch automatically depending on what amplifier is sending a signal? Or how do you activate the relay? Through a home assistant integration? What happens if both amplifiers are playing at the same time? Will the relay switch constantly?

Besides RCA switching, I would also like to do this for a pair of speakers.
Would this be safe you think? It’s not like the house is going to burn down, right? :slight_smile:

Many thanks already for this topic, it really helps understanding it all

10

Yep, that’s the wiring layout I’m using.

I’m using an HA automation to switch the relay. One of my zones has either TV audio or whole home audio playing on the speakers. For whole home audio, I have Chromecasts hooked to an HDMI-to-RCA Audio extractor. The RCA audio then goes to my RCA relay switch and then, if turned on, to the amplifier then the speaker. The automation in HA checks if my chromecast is “playing”. If it it the relay turns “off” which directs the Chromecast audio to the amp. If the chromecast is not “playing” it turns the relay on which directs the TV audio to the amp.

Here is my automation code.

alias: Patio Speakers - Switch between TV and WHA
description: “”
mode: single
triggers:

  • entity_id:
    • media_player.patio_speakers
      for:
      hours: 0
      minutes: 0
      seconds: 0
      trigger: state
      conditions:
      actions:
  • target:
    entity_id: switch.patio_speakers
    action: switch.turn_{{‘off’ if trigger.to_state.state == ‘playing’ else ‘on’ }}
1 Like
11

So if I understand correctly, you are switching the line level signal, before you amplify it. Is that correct? Do you see an issue doing the same with the already amplified signal?

The reason being is that I would like to be able to connect one speaker to 2 different amplifiers. One amplifier will be for the whole house system. The other amplifier will be a atmos aware amplifier.

12

I don’t think you will have a problem using the relay between the amp and speaker. As long as you are staying below the max amperage for the relay.

1 Like