Have you considered the Hypex instead? 700/500/380w at 2/4/8ohm? I'm going to guess, and others can tell me if I'm wrong, that up to the 225W capacity of the Purifi, you'd likely hear no difference between the two. https://www.buckeyeamp.com/shop/p/hypex-ncx500-amplifier-3-channel.
It's a minor issue. Just ask Dylan/Buckeye to send you the self-repair kit and instructions, or if you're worried about messing it up, send in the amp. Not a big deal at all.
Thanks, again, everyone. I got in line for a used pair of some of the speakers above. The ones that came up first were JBL 4309. Having moved from the 1970s to Wiim -> good DAC -> decent 80W NAD amp -> these speakers, my older lady friends are completely delighted. Classical, jazz, jazz vocals...
I'm helping my older women friends upgrade from a 1980 "college" stereo system to recently accessible near-audiophile quality equipment. Their new set-up is a new Wiim Pro streamer then to a SMSL higher-end DAC, then to their legacy 80W NAD amp (fine for now), and finally into cheap, old Kef...
Also, as an outsider, but a technical person, I'm impressed at how such a small flaw in the signal path showed up so clearly in the tests. Seeing this deepened my confidence in the proposition that this amp really is ultra-clean. Otherwise it'd show up in testing--as it did here. Pretty cool.
It's great news if that's the correct and final diagnosis. A few pennies worth of parts to drop in sure beats having to manufacture new boards. In the end it will have been a scary but ultimately good lesson on the need for up-front assured adequacy of testing procedures. The magnet test is also...
I thought for a few weeks that my DAC had stopped being recognized by my MacBook over USB. It had been working great, then I updated the MacOS operating system and BOOM it no longer worked. Haha. Just one of those stupid things: I had *also* changed the input USB setting to bluetooth. As soon as...
The least risky, lowest cost. high-payoff path will be to find the minimal satisfactory repair for the one outstanding issue, separating out any other modifications for another time.
Thank you, that sounds good. The community seems supportive. Late-found design issues are always a drag. Sorry a glitch got through. It'll be interesting to hear the diagnosis.