I’m working on a project with a 3W speaker and an electret mic. Both connect to a USB audio dongle (plugged into a Pi) through a long RJ9 phone cord, which only has four conductors. Usually, it’s two conductors for the speaker +/- and two conductors for the mic +/-.
The problem: both the speaker and mic are too quiet. I’m planning to use a PAM8403 to boost the speaker, but I need a good mic amplifier too.
I have a MAX4466, and it works great on its own, but once I run it through the phone cord, its VDD drops from 3.3V to 0.07V. Any recommendations?
When you say it “stops working,” is it too quiet again, or no sound at all?
Can you say more about how you have the cord wired in? I could think of a few reasons or degraded performance, but no sound at all makes me think let’s start basic (pinout, conductor continuity, connectors).
Thanks for getting back to me! I’m not sure if my last edit went through, so to clarify: the voltage at the MAX4466’s VDD pin drops from 3.3V to 0.07V when it travels across the cord, which means it likely isn’t getting enough power to transmit audio at all.
I’m considering running thin wires along the spirals of the phone cord to deliver the microphone’s GND, VDD, and OUT separately. I worry that the phone cord might be a poor conductor, since the speaker comes out a bit quiet through it too.
I found an alternative solution that works for what I need: I cut 10-foot lengths of 24-gauge wire and connected the MAX4466 to the Pi by concealing it through the loops of the phone cord. It’s definitely much messier, but that’s part of the fun of engineering.
That said, the MAX4466 is very difficult to work with over long distances since the analog signal picks up a lot of noise and interference. While I’m still proceeding with this method due to time constraints, I would definitely have tried other mics that handle noise better over distance if I’d had more time.
