A number of years ago we started to see more and more about cryo “treatment” of vacuum tubes. We read through all the marketing and tried to figure out how this could improve a vacuum tube. Our reaction was that it really didn’t seem logical that freezing a vacuum tube could improve it. We had concerns that the glass where the pins pass through would become compromised due to different rates of expansion and contraction of glass and metal. As well, it seemed odd that stronger steel could make a tube sound better. But to be thorough, we had carefully tested sets of matched tubes sent out to be treated so we could try it for ourselves. Our plan was to have two sets of tubes that had identical measurements. One set would be cryogenically treated and the other not. Doing this would allow us to do a comparison between the two sets and make the results less subjective.
The tubes were sent to a company that at the time was the premier provider of cryo treatments. After several weeks they were returned. A visual inspection showed they didn’t appear altered or damaged. After testing we found the measurements were not any better or worse, they remained the same. So far so good. Next was listening time. We set up a blind comparison test by having one person install the tubes but not allow the listeners to see which set was used. Our listening panel was a mix of audiophiles and studio engineers so we were confident subtle improvements would be noticed. Our results were very interesting yet anti-climatic. After several comparisons, we discovered that none of our listeners could hear any difference between the tube sets, let alone an improvement. No one could tell if or when a set was changed. If we could not hear an improvement, and we could not measure an improvement, we found it difficult to justify selling these “treated” tubes.
Since this time our friend Phil Taylor at Effectrode has written about his own thoughts on cyrogenic treatment of audio tubes. He’s been very kind and allowed us to reprint his article here.