Hello,
Here is my observartions I collected during my amp retrofitting to Purifi 1ET400A;
- SMPS1200A400 fits well to Purify eval board. You must switch aux voltages of SMPS1200 to unregulated (jumpers on board) since it is regulated by default.
- SMPS1200 does not have standby 5V power for external circuits e.g. remote controller so SMPS1200 must be On all time (energy consumtion is 9W in idle) or you need an additional 5V power supply if you need amplifier with extra features and standby mode.
- The Purifi eval board must have the +/- 18V unregulated voltage from SMPS, it does not matter if eval board in high or low gain mode
- Eval board low gain mode gives enough power with 4-4.5V from XLR DAC output for about 90dB senitive speakers to make listener deaf from 2m average listening distance. In this case DAC (X-Sabre pro) volume can be close to (slighly under) -1dBFS output level where Amir measured the best performance. I found this option; Purifi in low gain and X-Sabre close to "-1dBFS" gives the best stereo image.
- SMPS1200 has Amp Ena and Amp Err I/O pins, these are compatible with Purifi Amp Ena and Err pins. If you connect them, these will replace the on/off switch on the eval board (not necessary to desolder that) and you can do soft power on/off from SMPS.
- I hear a small hiss from tweeters when Purify eval board is on, but it does not grow at higher volume. In my next implementation I will try some shielding between Purifi power amps / Eval board / SMPS but I don't think it able to help.
- Shami the Cresnet SMPS maker guy promised to create new version of his SMPS600 to be compatible with Purifi board. Old version did not have the aux voltage named Vdr (-) necessary for Purifi amp board. Cresnet SMPS has standby power supply so a bit more advanced than Hypex SMPS, (except the Vdr voltage unavailability) and significantly cheaper.
- I found this cheap amplifier chassis to make my second, "pure" implementation, but it takes some weeks to arrive to Europe to start it.
https://www.ebay.co.uk/itm/WA97-Ful...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Overall, very easy to implement a nice sounding amplifier with eval board and it is so cheap comparing to other high performance amplifiers.
Merry Christmas!