I went through a similar process of comparing the results of different machines that I bought and used over time. The biggest difficulty in 'testing' is that, at least with old records, no two have the same 'history' of contamination (assuming that they are identical pressings that sound identical, which is a separate issue). I suppose David's approach of deliberately contaminating multiple copies of the 'same' record with the same amount of 'stuff' might yield some interesting insights. What I found, after a lot of playing around with different machines and 'problem' records was that some old records suffered from groove noise that I normally associate with irreparable damage to the record. But, repeated cleanings using different methods, including long enzyme soaks, point nozzle vacuum, ultrasonic, and in some cases ultrasonic wash, followed by point nozzle drying, did eliminate these problems on some records. My suspicion is that the stuff being removed was not only ground into the groove, but effectively glued down, - whether it was cigarette (or other smoke), cooking fumes, or a 'wipe' with some impregnated cleaning cloth, and years of all this stuff being cemented into the grooves, these nasties didn't come out in one or two cleanings. I'm now down to two machines- the current issue "big" Monks and a KL. The combination is very effective. And is worth some labor for valuable, hard to find old records. I'm also convinced there is merit to repeated cleanings using different methods- but in some cases, the records just aren't salvageable (at least to a high, quiet-playing standard). I don't think the new Clearaudio 'sonic' is necessarily a replacement for an ultrasonic machine, but may perform the 'agitation' function that is required with some fluids. Frankly, if the record isn't a 'problem' record, the different fluids seem to be less of an issue when using the Monks.
