Thumbs up for ultrasonic record cleaning

@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.

@whart Thank you very much for your informative input! This is similar to the process I'm currently using, but I do not rinse after the vac pre-wash since I US clean with the same solution as I vac (5% IPA + 0.05% Tergitol).
What do you use for your US cycle? Just high purity water?

@bydlo - i have not added any surfactant/detergent to the water since I’ve been using the KL. When I got it, I was using Reagent Grade 1, which seemed to be a waste of money. Now I just use distilled in the US, but for a finish rinse on valuable or challenged records, I’ll use the Reagent Grade 1 and vacuum on the Monks. As mentioned, when the KL goes, my plan is to try a DIY approach, largely b/c of the feature set, which includes the ability to use a surfactant to enhance cavitation effect.
For now, I just change out the bath water every thirty records, even though most of them have been precleaned. (Yeah, I’m a little compulsive, but I don’t have a filtering system hooked up to the KL).
Not to open a can of worms- I think this was discussed earlier in this thread- but the idea of alcohol and ultrasonic makes me a little nervous. I gather most of you are using only a small amount. Since I haven’t mixed any chemistry for ultrasonic, I can’t contribute to a meaningful discussion about what alcohol adds. I know in the old days, using vacuum, alcohol was commonly part of the cleaning fluid. I don’t think it is a terribly good solvent. Perhaps it is the evaporative properties. (I’m not concerned about damage to the vinyl since I think the exposure to the plastic is limited, but the flash point does concern me). Maybe I’m a nervous nelly.
There have been some good suggestions here on different chemistry. I use an lab grade detergent to clean my lab dishware which can be used in an ultrasonic machine. It isn’t very expensive. 1 part per 100 or 200 is recommended. It foams like crazy when I am hand washing the various glass I use hold brushes, and mix one of my RCM fluids (Hannl concentrate, which I dilute with the reagent water).  
I think there's a little Walter White in all of us. :)

@whart That's what I thought - KL discourages use of any add-ons no? Honestly, I'm sticking with alcohol just by some inertia. I like it for its grease dissolving properties. Also as far as I understand, it actually makes the 40kHz cavitation gentler by lowering  water's surface tension. Having said that, next tank solution I'm gonna try will be just water + 0.05% Tergitrol, excactly as used by the Congress Library and see if I get less clicks n pops. I also tried pure water US but I'm a bit afraid it may be too aggressive
plus I like the Tergitol solvent properties.

@fleschler 
You say, "I think your method of US is using 10 C degree too hot water and 100% too high a cavitation frequency. Maybe that’s why you can’t hear the difference on 3-6 posting; however you state you did see and hear the difference using this method on 2-6 post."

The one posting was about a routine involving 2 records at inadequate spacing, temperature, and rinsing. Improving these helped. The other posting was an experiment to explicitly test the hypothesis that one record would be damaged (it wasn't).

The differences were: more energy per record and very high temperature on one sector of the record in the test, higher temperature on the bulk of the record and better rinsing for the routine cleaning. Don't quite see how you conclude that 45C is too hot and US frequency is 100% too high. Also, don't quite see how this explains the results.

Cleaning efficiency vs frequency is graphed on the DIYAUDIO thread, if you are interested.