Wiring query about Teensy 4.0 and Audioshield rev D2

[Ozymandius]

I am trying to build the wedding audio guestbook project, and have it working using a test speaker and microphone.

The speaker is connected to the audio shield using the 3.5mm audio jack socket, and the microphone is connected to the MIC and GND points on the underside of the audio shield.

However, I am now going to be connecting it to the 'real' telephone (a GPO Telephone 322 mark1), and the speaker and microphone share a common wire:



BUT - looking at the Audioshield, on the underside it says "CAUTION: do not short VGND to GND":



- but I need GND for the microphone, and VGND for the speaker.

Does anyone know if I can either connect the speaker and the microphone common GND to VGND, or to GND?

 

[h4yn0nnym0u5e]

The caution means exactly what it says - don't do it, you will probably break the audio adaptor.

You either need to find a replacement cable, or fit an amplifier driven from the line level pins and sending its output to the speaker.

As the microphone is critical, I'd suggest you connect that (only) to the audio adaptor and see what the quality is like - a lot of folk seem to have issues in this area.