2. amps-preamps
  3. 1347156354

Amp hums in standby mode when TV is on

Hi, my Sherbourn 5/1500A power amp starts humming whenever the TV in the same room is operating. This occurs even when the amp is in its standby state, and also happens when using the amp(although you can't typically hear the humming at that point because of the sound from the speakers). What's more, as the image on the TV varies in brightness, the intensity of the humming/buzzing also varies. If the TV is off, the amp is dead quiet. I am assuming this is some kind of ground loop problem.

Should I try to plug the amp in with a "cheater plug"? There is a sticker on the back of the amp that indicates that the amp must be used with a grounded power cord.
mtrot
jea48
4,405 posts
 
Gbart,

Thanks for setting up and running the bench test experiment.

The reason I asked the question is so the user of a DC blocker could install the blocker on the known offending device or piece of equipment. In this instance the OP's TV instead of the power amp.

For those out there that are feeding their amp from a high dollar after market power cord would not have to add the DC blocker into the mix. The extra connections of another plug and receptacle plus the power cord or in the case where the DC blocker has an IEC inlet connector, another high dollar after market power cord.

The DC blocker reduced the audible level of transformer noise by about 2/3.

The million dollar question?

How does that compare to the audible noise lever of the toroid xfmr connected directly to the DC blocker?

Thanks,
Jim
gbart
290 posts
 
Jim,
I plan on doing a comparison of the blocker at the source of DC versus at the toroid. I could not do a thorough test the other night because I was working with exposed mains connections and wanted to make it quick. I will try again when I have a blocker properly assembled and enclosed in a box.

Glen
davehrab's avatar
davehrab
380 posts
 
IMO ... the DC offset created by the half wave bridge rectifiers in all the switching power supplies of our equipment is a silent killer

The Humming that is heard at the transformer is only the Symptom ... the real Disease is the loss of head room and reduced dynamics when the transformer’s efficiency is compromised by the DC off set saturating and rattling the transformer when that extra pulse is drawn

When a system is infected with RF you will hear the RF irritating you and effecting the high frequencies ... if your system has issues with EM (the magnetic side) ... you will hear a humming

But enough DC offset and the transformer’s efficiency is reduced and things just don’t sound as dynamic or authoritative ...

I feel you can clearly hear the effects RF and EM .. but a reduction in efficiency and head room is hard to realize until it has been corrected

I use two PS Audio Humbuster III’s in my system and was shocked at how much more powerful and authoritative the system sounded ... the character and tone of the system never changed ... it just sounded more powerful after unplugging everything from my EP15 Exact Power and plugging everything into the two Busters
More to discover