I use a Monks Omni-basically a reboot of the original Monks with some refinements, in combination with ultrasonics (like Mike, I have the KL, which has -knock wood- continued to function well though it is not new).
If I had to choose one machine, it would probably be the Monks. I do a wash cycle with different fluids depending on perceived need and a rinse step using high purity water.
The ultrasonic step adds another dimension to this which I like very much. I can use the ultrasonic alone for new records but for older grotty copies which have ground in contaminants, I find using something like AIVS #15, soaking and agitating, followed by a reagent grade water rinse, removes some distortion that ultrasonic alone did not. I encountered this several years ago on some high value collectible records, and since then, have employed a double cleaning method utilizing both.
Ultrasonic cleaning can be enhanced through the use of surfactants to lower surface tension of the water and increase cavitation effect. The biggest issue is then the removal of the surfactant after the ultrasonic process (if you are not using water alone in the ultrasonic machine). Some people are more sensitive than others to the residue left by the "cleaning" fluids-- here again, an extra rinse step helps.
If I were going to do an ultrasonic after the KL, it will likely be an industrial grade machine that is adapted for use in cleaning LPs, rather than a made for LP ultrasonic machine. This is not a cost-saving approach, though you can buy ultrasonic baths and the necessary equipment to rotate the records cheaply enough to put DIY ultrasonic into the "bargain" category. Instead, I’m looking for a more robust design, multiple frequencies, ease of cleaning the bath, filtering of the bath water for contaminants (not to filter out the surfactant), degassing and other features that tend to be associated with industrial ultrasonic equipment. The better med/tech machines, like the Elma, offer a lot of these features. The Zenith company, which builds full factory lines with multiple baths, offers a bench top (thanks, Neil!) that has an external power supply and is apparently built for industrial, not medical equipment, usage.
For what it’s worth, it is my impression that the high end community jumped on ultrasonic record cleaning largely due to convenience and got good results--many such users probably have new or pristine copies that were collected by audiophiles and ultrasonic alone may be sufficient for these. The more DIY ultrasonic approaches are less convenient than a one button "pop it in the slot and wait til the bell dings"- but offer more for someone who is crate digging and finding those jewels that need more attention. I’m not a Goodwill/Thrift Shop type record buyer, but rather someone who buys old private label and more rarefied jazz, hard rock and prog, dating back into the ’60s and earlier. Unless you find a sealed specimen (rare and has its own risks), you’ll likely encounter a record that needs some attention to achieve a high state of play.
PS: at the risk of exceeding my welcome by prolix prose, I also find that the vacuum of a record at rinse stage using the point nozzle type vacuum cleaner is more effective at removing residue and contaminants than the forced air drying typical of the "made for LP" ultrasonic cleaners. It sounds like a lot of work, but my processes have been simplified and I can roll through a stack of records in short order. I tend to clean in batches.
Oh, I had a VPI. A 16 that was converted to a 16.5 that I bought in the mid-’80s. That thing would not die. I gave it to a friend when I moved.
