after finishing my ES9018K2M project, I reworked an earlier prototype I built around a ES9023 DAC board. I wanted to build something that works with a power amplifier, as well as stand-alone with some bookshelf speakers, both on LAN and WLAN. It is powered by a 19V notebook-style power adapter and includes a 2x25W Class D amplifier.
Here are the ingredients:
- Raspberry Pi B+ board
- ES9023 DAC board from Audiophonics (also available on Ebay): 15 EUR
- TDA7492 2x25W Class D amplifier from Sure Electronics (on Ebay), with 19V ACDC adapter: EUR 24
- 1A DCDC converter (from Ebay): EUR 1
- Alps Blue Velvet stereo potentiometer 10k log (salvaged from a preamp I built 20 years ago)
- Hammond Electronics aluminum enclosure 22x16x5cm (could have been a bit larger, everything’s a bit tight): 24 EUR
- Edimax EW-7811Un WLAN adapter: 8 EUR
COB including the smaller parts like the speaker connectors etc roughly 120 EUR.
The 19V power adapter feeds the Class D amp board. From there I tap VCC and feed the 19V into a DCDC converter board, that outputs 5V for the Pi. A parallel line goes to an LDO, that feeds the DAC board with 5V. The current draw on that line is not that high, so that the power dissipation in the LDO is ok without adding a heatsink.
After fighting for a couple of days with a nasty ground loop, that made me hear ethernet and WLAN activity, I could solve this issue by breaking the loop, and isolating the Pi’s power supply from the DAC. No more noise.
The sound with my Cyrus power amp and my fullrange system in my office is really great, and the performance from the Class D amp with a pair of vintage bookshelf speakers is good, too. I yet have to do a direct comparison.