Yet another Loudspeaker Relay Switch

[Px2Pert]

Hi,
I need to build a system able to connect and remotely switch my 2 amplifiers (Both transistor based) with the same loudspeaker set (Right, Left and Sub out). I've already read many posts about loudspeaker switching (Considering both mechanical and DIY Solid state relay), but I need some suggestions.

The Switch control unit would be arduino (ESP8266) based, and both my amplifiers can be remotely controlled (RS232 and IR), so what i was thinking to prevent any sort of problems (like arcing) is:

• Remotely Switch off both the amplifiers outputs
• Select the "Active" amplifier via relay
• Switch on the Active amplifier

And talking about the relay: I was thinking about using a serie of DPDT, Latching relay consisting of:

• One Power Relay used for ground connection for both the loudspeakers
• One Power Relay for each loudspeaker positive
• One Signal Relay for Subwoofer ground connection
• One Signal Relay for Subwoofer positive pole

Should this be a good idea to build a safe Loudspeaker switch? Have you got any suggestions about the relay specs to find?
Why was a Latching relay never considered? It should be better as there is no signal needed to keep the NO state closed or is there something I've not considered specifically for loudspeaker DC output?

Thanks!

 

[Kay Pirinha]

I can't contribute that much to your question, just:

• I don't see any benefit for latching relays in your intended application, and
• do not use a commom ground relay for both speakers. Use two double pole relays instead.

Best regards!

 

[Px2Pert]

Hi,
Thanks for your support!
Ok, I'll go for a DPDT relay to individually drive each speaker!

Talking about why I'm preferring a latching relay:

• It keeps the same state even if the switch is powered off
• There is no need to keep active current flowing through the relay, so in case of troubles related to the switch itself (for example temporary loss of power) there is no risk to change the relay state

So shouldn't a latching relay be safer or am I missing something?

 

[PRR]

I may be wrong, but I see:

Latching relays have to self-hold so are usually lighter construction and not made for high current load

If the power goes out, you can't know what state the latch is in now (unless your CPU can remember over a power loss). The "safe" path is to have the CPU initialize in a safe state. This may even warrant dummy-loads if the amplifiers may be damaged by no-load.

 

[Kay Pirinha]

These were my thoughts also. Non-latching relays simply present a superior control-ability.

Best regards!

 

[Px2Pert]

Keeping the state in memory is not a problem (as i would save the state in the arduino eeprom for every switch).
What concerned me about latching vs non latching relay was exactly the construction, thinking that due to the fact that there is no need to apply an active force to keep closed the NO position, a latching relay would be more stable to sustain higher loads. Anyway I'll follow your suggestions and keep you updated.

Thanks for now!

 

[PRR]

no need to apply an active force to keep closed the NO position, a latching relay would be more stable to sustain higher loads.

While there ARE mechanical latching relays, most today seem to "latch" with small magnets. To keep electric demand low, very small magnets.

I have one on this desk. Here is a vintage LATCHING relay:

The electromagnet CHUNKs on the ratchet shaft. Cams work two switches A and B, alternately.