Andy's build log

I do this for a living. :slight_smile: FPGAs and microcontrollers and such, and for quite a few years. And because EEs are always engineers, I have personal projects, too, mostly involving audio.

Welcome! Looking forward to seeing how someone who does this for a living might approach personal projects differently!

Glad to have you here, Andy! What kind of audio? Instruments? Pro audio? GASP … Are you an audiophile? :wink:

This was something I cooked up to evaluate the performance of the TI PGA2320 stereo volume-control chip. It’s also something we use every day – I use little powered studio monitor speakers (KRK Rockit) hooked up to the TV, and for reasons I don’t understand the digital output of the TV doesn’t follow the remote control. (TV digital audio output goes into a cheap DAC.) So this box is simple: TI INA217 balanced receiver into the PGA2320 and out again using THAT1646 balanced drivers. The LCD shows the level using a simple bar graph. An encoder on the front panel controls the volume (press the button for mute). An IR receiver also controls the volume. I use the little Apple gumstick remotes which speak NEC.

LCD backlight level is adjustable, and it turns off after 5 seconds, and turns back on when the encoder is turned or a button on the remote is pressed.

A Silicon Labs C8051F314 is the brains. The PGA2320 uses SPI for control, driven by the micro. The micro handles encoder scanning and IR decoding.

Power comes from a 16 VAC wallwart. 16 VAC is rectified and creates +/-15 V for the analog, +5 for the PGA2320’s digital side and +3.3V for the LCD and the micro.


Audiophile? NO … bite your tongue! I’m also a live sound (front of house) guy, been doing that since forever. But mostly it’s useful stuff, like a studio monitor controller. I’m working on a reference-quality stereo ADC and DAC. I figure I could either spend a grand on one, or build one for a hundred bucks. (There is no sweet spot for DACs, either it’s crap for a hundred bucks or overpriced at a grand.)

Consider my tongue bitten :slight_smile:

Yeah, seems like there is an interesting “Branding” aspect to the high end DAC stuff. The thing where it could be the exact same chipset but a bit of branding and a wooden case/stainless steel volume knob increases the price by $800…