Seeking Advice: Best Preamp Design for Low-Noise, Balanced Microphones

[ccaudle]

Perhaps a job for a little ESP32 Arduino project.

Yes, perhaps OP can explain the archaic seeming requirement of setting gain using a DC voltage.

 

[DaveDC]

For a single preamp, an ESP32 controlling a PGA2500 or THAT 1580/5171 is a very good solution. The ESP32 would create a WiFi access point serving a web page that has controls for the preamp gain, pad, and phantom. Lots of example code on GitHub in both Arduino and MicroPython. No need to develop any code for the phone/tablet. Any browser would work. And the ESP32 is likely cheaper than the wire and connectors for the original control cable! The ESP32 could also handle a long-haul RS485/RS422 serial link if a wired solution is mandatory, with another ESP32 at the controller end.

If you wanted to have multiple preamps, a good way to control them all would be to use a Raspberry Pi running MQTT. This is a common multi-device protocol for home and factory automation. Each preamp would communicate to the MQTT server and hence would be individually controllable. A front panel dashboard for the whole network could be written in NodeRED, then accessed via any web browser. The Tasmota RTOS for ESP32 would be a very convenient and easy to use platform for this. It has a built-in MQTT support and scripting language called BERRY with which a custom driver for the PGA2500/THAT5171 could be written. Attached is a BERRY driver for an Austria Microsystems AS5043 Hall Effect angle sensor. It uses SPI, so it could be pretty easily adapted into a PGA2500 or THAT5171 driver.

 

[ccaudle]

controlling a PGA2500

PGA2500 runs from +/- 5V power supplies, it is made to connect directly to an ADC. If you want traditional pro-audio levels out of it (20 dBu or higher) you would have to add substantial amplification after the PGA2500. The That devices have a big advantage in that regard for analog output designs.