I have an issue.

I'm making a device that can switch between two microphones for a two way radio. The microphone that comes with the radio is an electret microphone that gets its plugin/bias power from inside the radio. This is 2.5V. The microphone that I want to connect to the device is also a electret but it needs 5-10V to work. I need to switch between these microphones with a relay. What is the best way to 'add' at least 2.5V to the plugin power?

Can I use a basic opamp? What would be the best circuit for that then?

edit: The radio i'm using is a telox M6. The box is built using this principle. if the 'zwanenhals ptt' is pressed, the ptt button on the radio will be pressed, and the mic wil be switched. (gnd is connected to the radio gnd via the 10-pin interface)

scematic of relaybox

The mic_in pin provides 2.5v bias power, and i need 5-12v Overview of the 10-pin in the front of the radio

  • 5
    \$\begingroup\$ Stack a CR2032 in series with the 2.5 V? How much current does the electret require? Usually FET based at about half an mA, isn't it? \$\endgroup\$
    – jonk
    Sep 14 at 9:59
  • \$\begingroup\$ You say you don't have access to any supply but you have 10V available from the connector pin 1. Why can't you use it? \$\endgroup\$
    – Justme
    Sep 15 at 11:08
  • \$\begingroup\$ @Justme Like, just inserting 10v (with 1k resistor) to the same port as the mic in? (just like a normal electret circuit). Wouldn't that break the MIC_IN port? (that always has 2.5v on it) (like this i.stack.imgur.com/H6pCC.png) \$\endgroup\$ Sep 15 at 11:33
  • \$\begingroup\$ Of course you won't leave the 10V DC bias to the signal fed to mic input if it can't handle it. So you could remove it. Maybe with a capacitor like how you apply the standard bias to standard mics. I am simply saying you do have a supply available even if you say you don't. \$\endgroup\$
    – Justme
    Sep 15 at 11:37
  • \$\begingroup\$ @justme I'm sorry, i dont see where i say i dont "have" 10 volts. My question is how to get a 10v bias on a mic that is connected to the mic_in port (which has a 2.5v bias) \$\endgroup\$ Sep 15 at 11:58


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