If your video system is connected to cable you may need to have your cable provider isolate the cable with a devise similar to the Jensen VRD-1FF.
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,Mechanical hum heard from the amp not through the speakers?
If yes then I would assume the power transformer of the amp is energized in the standby mode.
Good chance the sound you are hearing is coming from the power transformer of the amp.
If the buzzing, mechanical noise, is coming from the power transformer (only when the TV is turned on) then there is a good chance the switching power supply, SMPS, of the TV is putting DC offset back out on the AC mains.
Verify the sound is indeed coming from the amp's transformer and not through the speakers.
If that is the case You will to buy a DC Blocker.
Thanks, yes it is a mechanical buzzing, very loud at times.
It is my understanding that the power standby feature on this amp is designed such that when it receives a signal and switches on, it is supposed to be somewhat in a "warmed up" and stable status for good sound.
I will also see if adjusting the speaker and/or interconnect cables has any effect, which I doubt.
Thanks for the heads up.
Gbart, I have a question for you.... Assuming the TV's SMPS is putting DC back out on the mains what would happen if a DC blocker was installed between the TV and mains power receptacle? Would it block the DC offset voltage from the TV from going back out on the mains?
Jim,you asked an interesting question about something I hadn't thought of before. I tried a quick test with a pair of back-to-back caps bypassed by diodes, between a known source of DC offset (400mV) and mains. I connected a toroid transformer that is susceptible to DC on another branch circuit. The DC blocker reduced the audible level of transformer noise by about 2/3.
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?
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.
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 transformers 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 transformers efficiency is reduced and things just dont 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 IIIs 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