[DaveX]

Hi, I am hearing a mechanical hum from both my D200's transformers, this is in play or mute mode, no hum is coming from the loudspeakers, voltage is UK 230 volts. The hum is loud enough to be heard from my listening seat at 4 metres away, sometimes the hum is gone but "most" of the time it's audible. I am using Audusa Eupen CSA 2.5 power cords, I have tried a basic power cord, also disconnecting the earth wire. The hum is still present even with the interconnect and speaker cables removed.

My house is not known to have mains voltage problems. My old Cary power supply transformers only had a slight hum that was audible from 3 feet away and I don't use a power conditioner.  

I am awaiting suggestions from my UK distributor, he's going to contact Dusty.

By the way these are the most wonderful sounding amps I have ever heard. Thanks for any helpful suggestions.

[Charles Calkins]

I once had a terrible hum in my system after I bought a new preamp. It turned out to be feedback from the cable co. coax cables that I have to have for FM reception. I bought an FM and line cinditioner from Radio Shack and that took care of the problem. I guess the cables had some kind of leakage or else the new preamp was very sensitive.
 My D-200's are very quiet.


               Cheers
               Charlie

[halcyon98]

I had a hum as well that my other amp didnt pick up.

turned out it was from my cable

used a  Jensen IsoMax Digital RF Isolator VRD-1FF

and its all gone

[BobMajor]

Dusty has said previously that this is caused by power conditioners. It may be something else and I'm sure he'll reply when he gets back from CES.

[CIAudio]

D-200's are generally quiet, but waveform distortions can cause transformer windings to vibrate/hum. This is usually due to something else on the power line adding it's own waveform to the sine wave, but not necessarily in your house (could be a neighbors appliance).

We've seen this in a couple of instances, and since it's reality/real-world situation...we are working on solutions.

We'll be experimenting with potted versions of the transformers to see if they hum under these conditions.

[DaveX]

D-200's are generally quiet, but waveform distortions can cause transformer windings to vibrate/hum. This is usually due to something else on the power line adding it's own waveform to the sine wave, but not necessarily in your house (could be a neighbors appliance).

Some conditioners are current limiting, so I usually don't use them on amplifiers. Also some types restore the peaks of the AC waveform, which can cause mechanical hum from transformers. I didn't say you can't do it, but I prefer to connect them directly to the wall AC, and use conditioners for the low-level components.).

I've read above that you say a power conditioner can make the hum worse, is it worth trying any of them if I can get some on approval. Thanks.

[CIAudio]

Conditoners (filters) won't do anything to fix the wave form. Power re-generators create a better sine wave and can sometimes eliminate hum.
Exact Power makes a very good one, but I've seen these devices also  cause mechanical humt due to the restored peaks of the wave form (standard wall AC has flattened peaks).