Hum in Anthem MRX 700

[PENG]

Here I see the advantage of a switching power supply using a small transformer with a very unlikely risk of getting humming noise, and an additional advantage of consuming less power because of higher efficiency.

Good point, the smaller the transformer the quieter it will hum regardless of the cause, though the harmonics created by certain appliances and devices that use SCRs or other means for ac speed control could still wreak enough havoc to audible noise emitted from the transformer(s) unless you filter out the garbage before it hits the transformer primary (input) side. Harmonics related cause is not a common/major issue for hifi audio in the past but as more and more electronic speed controls and other high tech devices/appliances including TVs are being introduced into household, the probability for that to become an issue will increase.

 

[TLS Guy]

Good point, the smaller the transformer the quieter it will hum regardless of the cause, though the harmonics created by certain appliances and devices that use SCRs or other means for ac speed control could still wreak enough havoc to audible noise emitted from the transformer(s) unless you filter out the garbage before it hits the transformer primary (input) side. Harmonics related cause is not a common/major issue for hifi audio in the past but as more and more electronic speed controls and other high tech devices/appliances including TVs are being introduced into household, the probability for that to become an issue will increase.

And the RFI produced by those devices, is and will be, an even bigger issue over time. The more complex the system the more that issue multiplies. In my view this is already a bigger issue than ground loops, and much harder to analyse and resolve. More channels. more LED bulbs, more dimmers equals exponential growth of this problem. If you had in old house wiring and daisy chained neutrals then add another multiplier.

 

[PENG]

And the RFI produced by those devices, is and will be, an even bigger issue over time. The more complex the system the more that issue multiplies. In my view this is already a bigger issue than ground loops, and much harder to analyse and resolve. More channels. more LED bulbs, more dimmers equals exponential growth of this problem. If you had in old house wiring and daisy chained neutrals then add another multiplier.

Ground loop hum is well understood while RF and harmonics related issues are not so don't get talked about as much.

 

[TLS Guy]

Ground loop hum is well understood while RF and harmonics related issues are not so don't get talked about as much.

No, and what is worse I think they often get mistaken for ground loops as the symptoms are similar and overlap. Manufacturers need to do a lot more to make units more resistant to RFI. Shielding by itself is not enough. Unfortunately that will add to part count. The biggest bang for the buck is placing caps to ground across high gain solid state junctions so it does not get detected and rectified, and come out as a buzz from the speakers after being amplified down the chain.

Unfortunately a lot of the causation is in the design of the home and especially the lay out of wiring. So this means that problems have no easy solutions. This is something I had to really work at and minimize in the design, and electrical lay out of this home. I still had one issue rear its ugly head though, which did involve running another circuit back to the panel after the house was complete to cure it.

 

[PENG]

No, and what is worse I think they often get mistaken for ground loops as the symptoms are similar and overlap. Manufacturers need to do a lot more to make units more resistant to RFI. Shielding by itself is not enough. Unfortunately that will add to part count. The biggest bang for the buck is placing caps to ground across high gain solid state junctions so it does not get detected and rectified, and come out as a buzz from the speakers after being amplified down the chain.

Unfortunately a lot of the causation is in the design of the home and especially the lay out of wiring. So this means that problems have no easy solutions. This is something I had to really work at and minimize in the design, and electrical lay out of this home. I still had one issue rear its ugly head though, which did involve running another circuit back to the panel after the house was complete to cure it.

Yep, ground loop got blamed all the time even when it isn't the cause.

 

[mgood]

So here's a recording of the hum:
Anthem MRX 710 hum/buzz

You can hear a remote control click as I start an app which displays a dark image.

@PENG @TLS Guy

 

[mgood]

Tonight I noticed something new. The receiver hums with the TV off, but now the noise goes up and down and is not as loud. Here's a recording: Anthem MRX 710 hum/buzz 2

@PENG @TLS Guy @WMH

 

[AcuDefTechGuy]

The hum noise would drive me crazy.

Did you contact Anthem to see what they suggest?

 

[PENG]

Tonight I noticed something new. The receiver hums with the TV off, but now the noise goes up and down and is not as loud. Here's a recording: Anthem MRX 710 hum/buzz 2

@PENG @TLS Guy @WMH

That sounds very similar to that of my Parasound A21 whenever I had a particular portable humidifier running on high speed, low speed was fine iirc. So I think you TV is emitting certain kinds of harmonics that your Anthem's transformer is prone to react to, some sort of resonance but if it doesn't seem too loud so it is probably just the effect of high harmonic contents, probably mainly the 5th harmonic going by how it sounded to my ears.

You should contact Anthem for suggestions. If they won't help you then your best bet is to try some harmonics filters that may be build into a good quality power conditioner. Harmonics filters are widely use in industrial plants but for home audio I have never tried any so I have to say Google may be your friend.

Something like this should work:
http://www.powerqualityinc.com/harmonicfilter.html

In my case, it is not an issue because I only use that humidifier during the coldest/driest days in Jan and Feb, and if I am using the A21 at the same time I'll just set it to low speed.

 

[TLS Guy]

That sounds very similar to that of my Parasound A21 whenever I had a particular portable humidifier running on high speed, low speed was fine iirc. So I think you TV is emitting certain kinds of harmonics that your Anthem's transformer is prone to react to, some sort of resonance but if it doesn't seem too loud so it is probably just the effect of high harmonic contents, probably mainly the 5th harmonic going by how it sounded to my ears.

You should contact Anthem for suggestions. If they won't help you then your best bet is to try some harmonics filters that may be build into a good quality power conditioner. Harmonics filters are widely use in industrial plants but for home audio I have never tried any so I have to say Google may be your friend.

Something like this should work:
http://www.powerqualityinc.com/harmonicfilter.html

In my case, it is not an issue because I only use that humidifier during the coldest/driest days in Jan and Feb, and if I am using the A21 at the same time I'll just set it to low speed.

I agree, he definitely needs a power conditioner. He needs to stop this, as this resonance will loosen the laminations in the power transformer and his problem will get worse and may be quite quickly.

 

[WMH]

Don't forget such filter effects you mentioned are on the secondary side of the transformer not the primary on the incoming side.

The OP's transformer hum seems activated when he turned on his new OLED TV, if I can hear an audio clip I would be able to tell if it is due to harmonic resonance so hopefully he would make a recording for us to hear. It does not sound like grounded loop related kind of 120 hz (in NA) hum.

- There's only one place to put the units DC power supplies ... on the secondary outputs of the power transformer.
- The hum is intermittent, sometimes it will go away for almost a month. And it does not matter if the inputs(ie: DVD, Satellite, etc.) are on/off or if no input/outputs(except speakers) are even connected . The hum will eventually go away if the unit is repeatedly turned on/off.
- Also there is no physical hum in the power transformer.
- AC power in the US is 120V, 60HZ. The hum is 60HZ, someone got side tracked with the harmonic resonance lesson which is irrelevant here.
- Mgood's problem is different than the original post, his sounds like the TV produces EMF radiation getting into the Anthem. Could be the proximity of the TV to the Anthem or cabling locations.

 

[PENG]

- There's only one place to put the units DC power supplies ... on the secondary outputs of the power transformer.
- The hum is intermittent, sometimes it will go away for almost a month. And it does not matter if the inputs(ie: DVD, Satellite, etc.) are on/off or if no input/outputs(except speakers) are even connected . The hum will eventually go away if the unit is repeatedly turned on/off.
- Also there is no physical hum in the power transformer.
- AC power in the US is 120V, 60HZ. The hum is 60HZ, someone got side tracked with the harmonic resonance lesson which is irrelevant here.
- Mgood's problem is different than the original post, his sounds like the TV produces EMF radiation getting into the Anthem. Could be the proximity of the TV to the Anthem or cabling locations.

Sorry between you and mgood I got mixed up and referred to mgood as the OP when you are the real OP lol..
I don't know who you referred to as the one got side tracked? If you referred to post#20, that's the one I responded to your case and I never mentioned anything about harmonic resonance, until I responded to mgood's situation.

As you said, mgood case is different and I am almost 100% sure it is harmonics related, especially after hearing the audio clip. TV does not produce "EMF" radiation, there is no such thing actually. EMF is electromotive force, typically associated with motors, even moving coil loudspeakers. Did you mean electromagnetic field though? If so, I highly doubt that, TV won't generate strong enough magnetic field to affect the transformer inside a metal casing, even if placed right next to it.

I don't mean to give anyone any lesson, but as an EE for many year I simply tried to share some of my limited knowledge and experienced when I think it may be relevant.

Have you resolved your issues yet,? Please do share the result, thanks.

 

[mgood]

That sounds very similar to that of my Parasound A21 whenever I had a particular portable humidifier running on high speed, low speed was fine iirc. So I think you TV is emitting certain kinds of harmonics that your Anthem's transformer is prone to react to, some sort of resonance but if it doesn't seem too loud so it is probably just the effect of high harmonic contents, probably mainly the 5th harmonic going by how it sounded to my ears.

You should contact Anthem for suggestions. If they won't help you then your best bet is to try some harmonics filters that may be build into a good quality power conditioner. Harmonics filters are widely use in industrial plants but for home audio I have never tried any so I have to say Google may be your friend.

Something like this should work:
http://www.powerqualityinc.com/harmonicfilter.html

In my case, it is not an issue because I only use that humidifier during the coldest/driest days in Jan and Feb, and if I am using the A21 at the same time I'll just set it to low speed.

Thanks again, Peng. I will be contacting Anthem again, and I'll send them the recordings. I don't have much faith in their customer support, but it's worth a shot.

I'm having trouble finding a suitable power conditioners in Europe. Any suggestions?

 

[mgood]

Would something like this work? https://www.furmanpower.com/product/10a-two-outlet-power-conditioner-export-AC-210A E

 

[TLS Guy]

Would something like this work? https://www.furmanpower.com/product/10a-two-outlet-power-conditioner-export-AC-210A E

It might well. The problem is that the specs from Furman are very nonspecific and in terms of line filtering vague.

If you do purchase one, then you need a cast iron right of return if it not effective.

 

[Verdinut]

It might well. The problem is that the specs from Furman are very nonspecific and in terms of line filtering vague.

If you do purchase one, then you need a cast iron right of return if it not effective.

Maybe this one would do the job:

https://www.furmanpower.com/product/16a-power-conditioner-lights-voltammeter-220v-240v-export-PL-PRO DM C E

EDIT: A seller has a few brand new ones on eBay:

Furman PL PRO DM C E 16A Power Conditioner with Lights Volt Ammeter 220V 240V for sale | eBay

Find great deals on eBay for Furman PL PRO DM C E 16A Power Conditioner with Lights Volt Ammeter 220V 240V. Shop with confidence.

www.ebay.ca

 

[PENG]

Would something like this work? https://www.furmanpower.com/product/10a-two-outlet-power-conditioner-export-AC-210A E

As I alluded to before, harmonic filters are used in heavy industry but not usually applicable for home use . The popular conditioners such as Furman's typically deal with RF and EMI that supposedly could affect sound quality, but not transformer hum that are either due to poor design/build, or when activated by other devices in the house that spills dirt/harmonics.

Unless Anthem comes up with something (I doubt that too..), and if you can't return that TV set for something else, it is going to be a tough one to solve. You can also try using a long extension cable (temporarily) to feed the TV from a different outlet that is fed by a different breaker. Yes it will still be the same source but there is a chance there may sufficient attenuation to the offending harmonics this way. It is a long shot for sure.

Found a thread that people discussed harmonic issues and one fellow seemed to have build his own.

Are line harmonic suppression filters ever used for audio amplifiers?

Line frequency harmonic supression filters are quite common in power electronics for industrial use where lots of AC motors, inverters and welding and other power euipmenets are used. These usually supress the harmonic freunccy from 3rd to 20th harmonic and allows pure sine wave to the load...

www.diyaudio.com

 

[WMH]

Sorry between you and mgood I got mixed up and referred to mgood as the OP when you are the real OP lol..
I don't know who you referred to as the one got side tracked? If you referred to post#20, that's the one I responded to your case and I never mentioned anything about harmonic resonance, until I responded to mgood's situation.

As you said, mgood case is different and I am almost 100% sure it is harmonics related, especially after hearing the audio clip. TV does not produce "EMF" radiation, there is no such thing actually. EMF is electromotive force, typically associated with motors, even moving coil loudspeakers. Did you mean electromagnetic field though? If so, I highly doubt that, TV won't generate strong enough magnetic field to affect the transformer inside a metal casing, even if placed right next to it.

I don't mean to give anyone any lesson, but as an EE for many year I simply tried to share some of my limited knowledge and experienced when I think it may be relevant.

Have you resolved your issues yet,? Please do share the result, thanks.

- MVW and I have the same problem with our Anthem’s. Were on this post to see if anyone has had the same problem, what resolved it and what it cost to have it fixed.

- I actually have an Electronics Engineering Degree and nearly 50 years experience, I do know what I’m talking about.

- Mgood's problem is different than the original post, his sounds like the TV produces EMF radiation (or EMI: Electro Magnetic Interference) getting into the Anthem. Could be the proximity of the TV to the Anthem or cabling locations. It has nothing to do with “Harmonic Resonance”.

Here’s the lesson you must have missed when you went to college:

Electromagnetic Field (EMF) Radiation Spectrum
EMF radiation can be classified from very low frequency (long wavelength) to very high frequency (short wave length) as show below.

I'm out of here!

 

[PENG]

- MVW and I have the same problem with our Anthem’s. Were on this post to see if anyone has had the same problem, what resolved it and what it cost to have it fixed.

- I actually have an Electronics Engineering Degree and nearly 50 years experience, I do know what I’m talking about.

- Mgood's problem is different than the original post, his sounds like the TV produces EMF radiation (or EMI: Electro Magnetic Interference) getting into the Anthem. Could be the proximity of the TV to the Anthem or cabling locations. It has nothing to do with “Harmonic Resonance”.

Here’s the lesson you must have missed when you went to college:

Electromagnetic Field (EMF) Radiation Spectrum
EMF radiation can be classified from very low frequency (long wavelength) to very high frequency (short wave length) as show below.
View attachment 33960
I'm out of here!

In the EE world, EMF generally refer to electromotive force, so it is better to refer to electromagnetic interference as EMI. The effect of "EMI" is more appropriately described as interference (I) than force (F) anyway. To be clear, it wasn't the terminology I wanted to discuss/or argue with you, but just wanted to be sure if you were referring to EMI when you used the term EMF. I thought I was polite and open minded on this and I am sorry if I offended you inadvertently.

To @mgood , WMH could be right as EMI could certainly do something like that too, I didn't think it would be in you case because I thought people don't typically put their AVR so close to their TV such that the EMI effects would be strong enough to result in such audible hum, but may be you do...

I never said (or at least meant to say) it was harmonic resonance as that would be the worst case scenario only. It does not need to be in resonance to create the kind of noise. I cited my own experience with my desktop humidifier that was in another room more than 15 feet away, separated by a wall, and that I knew for sure was due to harmonics, not EMI, obviously the expression ymmv/mgood's mmv applies here.

 

[highfigh]

Do you have cable TV? If so, disconnect the cable from the cable box and if the hum stops, call the cable provider and tell them to get their butts out to fix THEIR problem.