Thumbs up for ultrasonic record cleaning

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)?

@whart - Thanks for your thoughtful response. The general consensus seems to be that US RCMs do not cause any damage; I suspect that if any microscopic changes (damage) are occurring, it is subtle, random, isolated and cumulative, possibly evading detection via listening tests for several cycles.

I also suspect that given the number of variables, the amount of cleansing action (and by extension, over cleaning and possible damage) varies greatly with each application. I doubt that damage would be heard as an average degradation across the entire LP, but would be random and very limited until it became severe enough. My thought process is to better understand the mechanics of US cleaning in order to optimize the cleaning process while minimizing the potential for damage. My impression after reading this thread (and others) is that few people using these devices fully understand what is occurring and are relying on mfrs specs and hoping for the best. My impression of the electronics driving the KLAudio transducers is that of a very simplistic approach, adjusting one important parameter (frequency) in order to obtain a desired specification (power) without fully optimizing the process.

Some of the industrial tanks vary the frequency and therefore the power to create "waves" of transmitted energy to improve the cleaning process. While the average power may be 150W, the peak power could be many times higher. The KLAudio machine maintains constant frequency, but the DC supply to the output transistors is essentially unfiltered rectified line voltage so the transducers "pulse" at 100/120Hz with peak power ~280W.

FYI, I use both IPA and surfactant (tergitol) in my KLAudio RCM for the past 2 years. I know it voids the warranty, but so far, I have not experienced any bad side effects.  I also vacuum the records after cleaning with an Okki Noki.

@fleschler- You have it backwards. A higher frequency US will have lower energy release and it will be much more evenly distributed than lower frequency. The cavitation bubble size is inversely proportional to the frequency; the higher the frequency, the smaller the bubbles and the lower the energy release when they collapse. The smaller bubbles are also more effective at removing smaller particles than larger bubbles (lower frequency), especially between the grooves. The Kirmuss RCM is closer to an industrial cleaner and should be avoided IMHO.

Higher temps facilitate cavitation and will increase the energy release, which may not be desirable if you are worried about damage. Adding surfactants and IPA will also increase cavitation. Whether this is advantageous or not depends on frequency, power, chemistry of the bath, distance from the transducers, volume of the tank, coupling efficiency of the transducers and matching of the drive signal for both impedance and frequency of the transducers.

So........pretty much a waste of my time posting here.

Guess I'll try another website.

Over and out.