Class D amplifier hum?

[Barry (NJ)]

Well I've tried a number of different Class-D amplifiers in my home; Digital Amplifier Company, Class D Audio, and now some B&O ICE module based amps, and all have put audible hum through my speakers. My Audio Alchemy OM150 amps have some transformer hum, but that hum does not come through the speakers. I find it odd that all the Class-D amps I've tried hum, but my Class-A/B amp does not. Is this something that is problematic with the AC I have coming from my wall, and is it something inherent in the design of Class-D that lets it manifest itself, while my Class-A/B amp filters it?

[mfsoa]

Have you ever measured for DC on your AC lines?

Can this even be measured with a simple multimeter or does one need more sophisticated equip?

Have you tried other preamps/sources?

Sorry, more questions than answers from me!

[Response Audio]

It sounds like AC issues. This may also be what is causing the transformer hum in your OM 150 amps.
Another option could be the grounding scheme within your preamp. To ask the question again, have you tried more than one preamp?

How bout cables? Make sure that any interconnects that are running near AC cables are doing so at 90 degree angles.

Lastley, if you have not already done so, disconnect everything from the preamp leaving only the amplifier connected. If you have cable TV, unplug the power cord to the cable/receiver box and make sure the cable coming into the house is nowhere near your system cabling.

[Barry (NJ)]

First, thanks for the ideas

Well I only have 2 pre-amps, and they are both the same model, an Audio Alchemy DLC. I have had other pre-amps installed here when a friend brings one by. Mike(mfsoa)'s VAC, with it's balanced outputs doesn't seem to cause any hum when used with a Digital Amplifier Co. Cherry in my system. There are no cable boxes near my audio rig, actually, no cable boxes in my house, I just run cable direct to my TVs and what we get is what we get, I only pay for basic cable so have no need for a cable box and there is no cable-TV near my audio rig either. Also, I'm pretty careful about my cable dressing, though it is a jungle back there

I found this thread over at DIY Audio...

http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html

I haven't finished reading it yet, but maybe it holds some info for me

[Response Audio]

Sounds like you could still have noise from the preamp if the VAC does create noise in your system.
This could be as simple as a ground issue as this is an important issue with digital amps from what I have found.

I would double check the possibility of a ground loop. Have you tried lifting the ground on either the preamp or amp without any sources connected? 

[Barry (NJ)]

I haven't tried lifting a ground, but FWIW, all my equipment is connected to the same outlet, so ground differential shouldn't be an issue. I'll grab a cheater plug and see if that makes any difference.

[eleazar]

Barry that ClassD of mine had a hum until I pulled off the ground wire inside. After that I had no noise at all from it. When you had it the ground wire was removed..........Bill

[Barry (NJ)]

Thanks Bill, you know I can't remember if yours hummed when I used it here, I do remember that Deepak's did, and I've had a couple of Tommy's amps here at different times, and now the B&O amp that Jim lent me, and all of those have had the issue.

[shadowlight]

Thanks Bill, you know I can't remember if yours hummed when I used it here, I do remember that Deepak's did, and I've had a couple of Tommy's amps here at different times, and now the B&O amp that Jim lent me, and all of those have had the issue.

Mine had the ground active.

[rollo]

  The first rendition of the Arion HS500 class "D" hybrid amps hummed a bit as well.  Just lifting the ground did the trick on the first model.  Since then the power trannie was changed. No more humaroonie. Dead quite.
   Barry by any chance did you try lifting the ground on the CDP/DAC ? It can be a culprit as well. Good luck.


charles
   

[Barry (NJ)]

   Barry by any chance did you try lifting the ground on the CDP/DAC ? It can be a culprit as well. Good luck.


charles
   

My CDP doesn't have a 3 prong plug, so I'm not sure how I would go about lifting its ground.

[Response Audio]

Your CD player does not use a ground so that is not a problem. Your noise testing should be done with no sources connected. If you are going to lift a ground, do so on the amplifiers and let the preamp serve as the ground point of the system.

[rollo]

   Barry by any chance did you try lifting the ground on the CDP/DAC ? It can be a culprit as well. Good luck.


charles
   

   Well obviously you cannot. Is the plug polarized, meaning a larger blade for neutral. If not try reversing plug, if so oh well.
    Bill or Tommmy should be able to help you out.


charles

My CDP doesn't have a 3 prong plug, so I'm not sure how I would go about lifting its ground.