In mid-January, I mentioned (above) that after talking with Steve, I would send my Torii MKIV back to IL to inspect for anything causing the hum I had experienced. After just a couple of weeks or so, it returned last week.

As one might have expected, Steve found nothing wrong, and the level of hum found was within the expected levels of acceptance. Knowing that is helpful as I can now eliminate the nagging question of whether something is wrong with the amp. He did say he made some adjustments but could not predict how they would affect performance in my environment.

The good news is that the hum is less to my ear. It is now similar to the hum produced by my SE84UFO when placed in the exact location. For both amps, the hum cannot be heard from the listening position 10-12 feet away from the speaker. I can pick it up from two feet, but that is not an issue.  

From my talks with Steve and my exploration over the past 14 months with hum management, I conclude that it is common for some Decware amps to hum. It is how loud they hum and how that affects the listener.

Steve said the challenge is to design an amp with great dynamics and minimal hum. One could eliminate all hum, but at the cost of a higher quality sound. It is a balancing act.  

I should add one other newly discovered issue. After a year of daily amp use, my power tubes failed - or at least one did. Not to discount what Steve may have done by working around the edges when he had the amp, the change of power tubes might account for current hum improvement.