A. Just got one of these and it works like a charm. Previously I had intermittent hum/buzz from the transformer. Sometimes none, sometimes a little, sometimes very strong and loud. Now I don't have any.
B. Frank, question: any reason not to put a spike/surge prevention device or a free standing voltage regulator either before the Humdinger or between the Humdinger and the amp? I'm asking because I have some bad power issues occasionally where I live.
C) BTW, for others: AFAIK, the typical symptoms of DC pollution on the line is that it is intermittent, and that it varies in intesity. It can be measured by a pro. But if you don't have that option I was advised to check the situation this way:
1. Wait till you are alone at home. Unplug everything in your home from the wall sockets. Yes, everything.
2. At your fuse box, turn all the breakers to off.
3. Plug in your amp and turn it on - disconnect from rest of system first, of course.
4. Turn on the switch/breaker that supples power to your amp. Listen for the buzz.
5. Sequentially turn each breaker on and listen each time for the buzz. Continue till all breakers are engaged.
6. If you have no buzz, begin plugging all your devices back in and turning them on. After each one is done, check for buzz. If the buzz begins, you've found your culprit - it could be a computer printer or some other device.
7. If you've engaged everything and have no buzz, then the problem may be DC on the line being created by a neighbor or anything in your area on the same transformer as your place. At my house we suspect the satellite TV installations in the neighborhood. Run your amp for awhile normally and if the buzz starts again, its probably from something external to your home.
Obviously this is easier if you have 2 people, especially in a larger home. But in my home it actually didn't take long to do.