Thumbs up for ultrasonic record cleaning

Thank you for the references, which mainly point out that there is very little formal research on US cleaning, beyond the obvious and the theoretical. Let me give you another reference: the Rushton thread (2016) here on Audiogon, to which I contributed extensively.

It seems that we mostly agree, but:
1) temperature. Your references suggest that low frequency US cleaning might be more effective at removing fats and oils. As I mentioned in the Rushton thread, I had thought so too until I found that it was a temperature effect. The lower frequency US did a better job of cleaning oils, while heating the chemistry more. When I controlled for temperature, the low frequency advantage disappeared. So I use 80KHz, sweep function, and 45C.
2) frequency mix - see above.

By the way, I have done a fair bit of trial and error, including 2000 odd records which were inadequately rinsed! So I had to do the whole lot again, with a better regime: rinsing under running highly purified water followed by a distilled water bath. Air dry in a clean-ish room.

By TDS I assume you mean total dissolved solids. I use distilled water for cleaning, so total dissolved solids is very low - for the first 2 records. Naturally that increases with each pair. That increase is roughly indicated by the colour of the chemistry, which is close enough for hobby work. For suspended solids, I allow the chemistry to settle and use the valve on the ElmaSonic to drip solid-free chemistry into a jug. I use VersaClean 2.5%.

By IPA, I assume that you mean isopropyl alcohol. I don't use anything volatile and flammable, because, while it is easy to monitor and regulate vapour in a lab, it is hard in a garage. Since my Elma machine can be an ignition source, I avoid the hazard.

I also see that you are cleaning 6 records at a time, which means a spacing of at most 33mm. That spacing is OK for 80KHz, about 1.7 wavelengths, but, at less than a wavelength, that spacing is quite inadequate for 37KHz. Also, with 6 records your effective US power per record is down to about 55W. I find that I get better results at 75W. YMMV

I also see that you are cleaning 6 records at a time, which means a spacing of at most 33mm. That spacing is OK for 80KHz, about 1.7 wavelengths, but, at less than a wavelength, that spacing is quite inadequate for 37KHz. Also, with 6 records your effective US power per record is down to about 55W. I find that I get better results at 75W. YMMV

@terry9

Pardon me for being sceptical about the utility of either of those statistics.  I'll tell you my thoughts and then you can explain.

I don't see how the wavelength of a given frequency is relevant to the space between records. If you're saying a given wavelength, say ~40mm for ~37kHz (water, 30-degree C) is too wide to fit between a 33mm space between records, I don't see how that makes any difference.  The frequency determines the number and size of the vacuum bubbles generated that will implode against the record in solution - that is the cleaning force.  My Elma has 6 transducers on the bottom of the tank and they will generate the same number of vacuum bubbles at a given frequency regardless of the spacing between records. I don't see how a wavelength greater than the distance between records changes ... what ?  - the access of bubbles to records, as if that wavelength limits how many vacuum bubbles get to the records?  I don't see it.

The claim of higher watts per record is based on having fewer records in a given tank. I don't see why the ratio of records to watts makes a difference.  The same number of watts will be output regardless of the number of records. Granted there are more bubbles per record with fewer records but the records are in a fixed position and the total bubbles in the tank at any given time is the same independent of number of records. It's not clear that fewer records 'attract' or receive more bubbles than a greater number of records.

Wrt frequency: There is a correlation between particle size, particle tenacity, the efficiency of particle removal, and frequency.  If there was relatively constant particle size on a record we could target the frequency to that.  But given the state of used records, there is no such constancy. From a visible glop of something to a few microns, multiple frequencies target a broader range of dirt.


Btw, which Elmasonic model do you have? As you read, mine is the P120H..

When I tested spacing (using SQ as the determining criteria), in my Chinese 10 L/40khz tank, spacing two records at 2" apart has superior SQ, opposed to 1" apart. I could hear the difference.

@jtimothya

Your example of particle size is unconvincing to me. A ’visible glop’ is made up of tiny particles which can be broken loose by US action, and then either deposited as solids or taken into solution as solutes, or perhaps even suspended. It is not necessary (or desirable) to remove the blob of glop all at once - a 1/4" glop would respond best to a frequency so low as to be reminiscent of a file.

With respect to frequency, my reasoning is as follows.

Bass response is a good analogy because both are sound waves in a confined space. Low frequency energy will be present in a listening room regardless of size - the problem is that different frequencies will manifest at different points. The mechanism is constructive and destructive interference. This is a function of reflections and dimensions (spacing).

If you want really good bass response down to a given frequency f, then the room should have at least one distance equal to or greater than c/2f, where c is velocity. Better is c/f, or even more.

By analogy, record spacing will affect the distribution of energy on each record surface. For a uniform distribution of energy (bubbles) which washes the entire surface, at least one wavelength is required. Consider the case of the US cleaner in Imperial measure, as it is more convenient. Then c ~ 5000 ft/sec = 60,000 in/sec. At a frequency of 60KHz = 60,000Hz, a wavelength is 1 inch. At 80KHz, wavelength is 6/8 = 0.75". Of course, records are not planes; they wobble on the spindle, they are slightly warped, etc. Therefore a safety factor of 1.5 to 2 is sensible, for 1 1/8" to 1 1/2" at 80KHz. I use 2".

By theory, the definition of energy is the ability to do work. The work in this case is microscopic bubbles on the surface to be cleaned. Since we know that low frequency US heats the chemistry much more than high frequency US, much low frequency energy is used to heat chemistry rather than clean. That is, the energy is expended elsewhere than on the surfaces. This is evidence that spacing matters.

By experiment, try cleaning a pipette in an ultrasonic bath. If anything is caked on the inside, it will take forever to come clean. The US agitation is negligible in such a confined space. Also, I tried close spacing and had to re-clean nearly a thousand records. I got as much suspended solids off during the second cleaning as I did on the first.

Your analysis of energy may well be correct. Thank you for enhancing my understanding of this by forcing me to think more about it. But in our practical case, it comes to the same thing - something is happening, so either we increase spacing (and reduce the number of records) or we reduce the number of records (and increase the spacing).

In conclusion, the direct evidence is: fewer records with greater spacing removed more solids. This experiment, however, does not differentiate between two potential causes: spacing and energy/record. Both interpretations of theory come to the same thing: fewer records, widely spaced, is better.