Amp transformer buzz/hum from DC on AC line?

An update to my previous post.

Listening to a wider spectrum of music while using the Humbuster III, the amp still is dead quiet. But I have also found that the unit removes a very slight amount of detail from the music, what I'd call a slight reduction in higher frequency. Most notable on the leading edge of acoustic string, voices. And by this it affects the definition and air about the same.

I'm going to continue playing for a few months and see if it's a case of needing burn in (always suspect of that, but had a good example of it a while back with an upgrade of power cords and better IC's). We'll see. Nice to see the hum removed, and the amp is running cooler, but not happy with the cost of doing that.

Someone had mentioned in this forum something about this unit that was contrary to what was thought as it's sole efffect i.e. DC removal. The documentation with the unit states 'over/under voltage surge protection' so I'm not certain just what goes on within and if something beyond the DC removal contributes to this attenuation of detail.

Do we still think the humbuster filters some higher frequency detail from the output of the amplifier?

One thing I can say is that the humbuster works well on toroidial type transformers, but not really on EI types. There may be some exceptions, but that's the effect I have noticed on a variety of amplifiers and other gear.

Are you sure it's not related to a dvr motor running? Not sure if you have a dvr but they can cause a racket if not isolated.

If your amps do not have capacitors blocking dc at the input, then the amps will amplify dc and you will hear it on the output or the amp's dc protection circuitry will shut it down. It sounds as if you have excessive dc offset on the amps. or from the pre-amp. if the amp does not have a dc offset adjustment, then it is possible that a device in the amp has or is failing causing a dc offset. you would have to open it up or take it to a qualified tech to check each component for correct operation or failure and replace/repair as necessary. If you disconnect the amp from all other equipment,plug it in and turn it on and the dc offset is still there, then it is the amp and must be repaired. amplifiers that are well designed will amplify any signal, be it ac or dc. dc at the input will cause big problems if the amp doesn't have dc protection circuitry. Such as blown amps or speakers. or if it does have such protection, it will simply shut the amp down until you find and fix the dc offset problem. If your power supply filtering isn't up to snuff, the dc on the ac line may find its way to the audio amplification path. So, if this is the case, you may want to check the power supply capacitors and bypass capacitors to see if they are leaking, going bad or failed. Or add some bypass capacitors if they aren't any there. DC on the ac line shouldn't be there. But if you can't find the source, then an ac isolation transformer or a power line conditioner is necessary.

enjoy