I’ve been following this thread for some time now, very interesting reading and thanks to all the contributors.
Some observations:
I owned one of the original AD US cleaners and was not impressed with the results or the build quality. I replaced it with a KLAudio KD-CLN-LP200 with (IMO) much better build quality, but still unimpressive results. I’ve looked at the DIY machines and have been reading everything I can get my hands on wrt to US technology. There seems to be a considerable difference between low frequency US cleaners (28kHz) and higher frequency (80-100kHz), the former used primarily as industrial cleaners (car parts, large metal components etc), the latter used for more delicate structures, especially fine jewelry. The cleaning action is created by the collapse of the cavitation bubbles which can create extremely high pressure (10’s of Mpa) and high temps (5000°C), but on a very small scale, determined by the size of the bubbles: The lower the frequency, the larger the bubbles and the more concentrated the released energy. On high power, low frequency US machines, this process can be so aggressive the sides of the stainless steel tank are subject to etching.
I was curious about this, so I did some measurements on my KLAudio RCM which is assumed to be 40kHz. It actually runs at 34.72kHz which would seem to be more aggressive, almost midway between 28 and 40kHz. There was a frequency adjustment pot, and I monitored the AC power being consumed as I adjusted the pot. Increasing the frequency lowered the power consumption and lowering it increased the power; at 33kHz, it went from 200W to almost 350W. The power consumption also changed drastically between running the cleaner with and without a record (200W with vs 150W without) indicating that the load seen by the transducers affect power consumption and the load changes with mass, density and distance from transducers.
So my question is this: With so many variables affecting the performance and operating parameters of the US process (temp, surface tension, power, frequency, cavitation efficiency), how does one know what they are really getting and what they are doing to the record surface (not only whether it is effectively being cleaned, but whether it is being damaged in the process)?