Hum in Anthem MRX 700

AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
- 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!
So in your 50 years of experience and knowledge with the Electronics Engineering Degree (is this the same as Electrical Engineering Degree?), what is the problem with Anthem? And do other AVR brands have this same problem?
 
W

WMH

Audiophyte
So in your 50 years of experience and knowledge with the Electronics Engineering Degree (is this the same as Electrical Engineering Degree?), what is the problem with Anthem? And do other AVR brands have this same problem?
Back in the 70’s it was called an Electrical Engineering degree, my elective coursework concentrated on analog and RF design. I’ve always worked on the Electronics side as opposed to Industrial.

I’ve set up the unit with just one speaker connected, but of course since the problem is intermittent, I could not get the hum to start. Tapping on the circuit boards had no effect. My intention was to isolate problem to a circuit board with an oscilloscope and then look for cold solder joints or possibly a bad component.

From what I’ve heard, Anthem doesn’t share/sell their schematics so troubleshooting could be difficult. It’s most likely the same sentiment as they only sell product though authorized dealers.

I’m surprised MGOOD even has his problem in Norway since EMI standards are much stricter in Europe than the US.
 
P

PENG

Audioholic Overlord
I think we are just guessing at this point..

mgood said:

- the hum is in coming from the unit itself, is constant regardless of the volume position (ref post#30), a real pain when he installed a LG OLED TV. I take it that it would hum even without any speakers connected, but that's just my guess.

- the he reported that "The receiver hums with the TV off, but now the noise goes up and down and is not as loud. ..." (ref post#47)

- he attached an audio clip of the hum in post#46, it did not sound like the typical grounding related 60/120 Hz or 50/100 Hz in part of Europe hum. It sounded like higher order harmonics

So again, it could be EMI related, but I do doubt EMI from that TV (even when it was off) would be so strong to make the transformer (again, his post#30 indicated the noise did not come from the speakers) hum that loud.

I remain curious about the real culprit and hope he will let us know when he eventually narrow things down.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
Back in the 70’s it was called an Electrical Engineering degree, my elective coursework concentrated on analog and RF design. I’ve always worked on the Electronics side as opposed to Industrial.

I’ve set up the unit with just one speaker connected, but of course since the problem is intermittent, I could not get the hum to start. Tapping on the circuit boards had no effect. My intention was to isolate problem to a circuit board with an oscilloscope and then look for cold solder joints or possibly a bad component.

From what I’ve heard, Anthem doesn’t share/sell their schematics so troubleshooting could be difficult. It’s most likely the same sentiment as they only sell product though authorized dealers.

I’m surprised MGOOD even has his problem in Norway since EMI standards are much stricter in Europe than the US.
In my 30 years in this hobby, I've only used AVRs from Sherwood, Harman, Denon, Marantz, Pioneer, Sony, and Yamaha. And I have never seen a case where these AVRs would produce any kind of HUM noise like the 3 cases here with these Anthem AVRs.

I've had cases of ground loop hum noises with various amps in my previous homes, but never with an AVR.

Definitely gives AVRs a bad name and more ammunition for @TLS Guy race against the AVR-machines. :D
 
P

PENG

Audioholic Overlord
In my 30 years in this hobby, I've only used AVRs from Sherwood, Harman, Denon, Marantz, Pioneer, Sony, and Yamaha. And I have never seen a case where these AVRs would produce any kind of HUM noise like the 3 cases here with these Anthem AVRs.

I've had cases of ground loop hum noises with various amps in my previous homes, but never with an AVR.

Definitely gives AVRs a bad name and more ammunition for @TLS Guy race against the AVR-machines. :D
So AVRs are machines now:D:D, thanks to TLS?
 
M

mgood

Enthusiast
I think we are just guessing at this point..

mgood said:

- the hum is in coming from the unit itself, is constant regardless of the volume position (ref post#30), a real pain when he installed a LG OLED TV. I take it that it would hum even without any speakers connected, but that's just my guess.

- the he reported that "The receiver hums with the TV off, but now the noise goes up and down and is not as loud. ..." (ref post#47)

- he attached an audio clip of the hum in post#46, it did not sound like the typical grounding related 60/120 Hz or 50/100 Hz in part of Europe hum. It sounded like higher order harmonics

So again, it could be EMI related, but I do doubt EMI from that TV (even when it was off) would be so strong to make the transformer (again, his post#30 indicated the noise did not come from the speakers) hum that loud.

I remain curious about the real culprit and hope he will let us know when he eventually narrow things down.
I'm planning a barrage of tests and will keep you posted. Still waiting for the DC blocker, and will probably try and Isotek and maybe a Furman as well. The Anthem is in fact due for retirement soon, so I will also be borrowing a NAD T777 v3 (toroidal transformer) and a Denon X6500 (e-core transformer) to see how they behave. Will also try connecting to a different power socket.

About proximity to the TV: the Anthem is approx. 5 feet from the TV in a new Atacama rack with spikes. Might be my imagination, but the hum seems to have changed somewhat in character since I installed the rack. The receiver was previously in a IKEA unit. This would indicate a harmonics issue, no?

To everyone who has chimed in so far: thanks for all the feedback and suggestions.

To the OP: sorry about the thread hijack. I hope this thread can serve as a resource for other Anthem owners with similar issues.
 
P

PENG

Audioholic Overlord
I'm planning a barrage of tests and will keep you posted. Still waiting for the DC blocker, and will probably try and Isotek and maybe a Furman as well. The Anthem is in fact due for retirement soon, so I will also be borrowing a NAD T777 v3 (toroidal transformer) and a Denon X6500 (e-core transformer) to see how they behave. Will also try connecting to a different power socket.
I have never had a Denon hum on me. The X6500H, imo is superior to the T777 V3, unless you believe Dirac Live is superior.:D Toroidal is not always better than EI core, both have pros and cons, those in general they are lighter for the same VA rating. Yes all else being equal they have less leakage flux too but Denon's E-I core transformer are well build and you can typically see the copper foil/strap shielding on the outside to help minimize leakage flux.

The receiver was previously in a IKEA unit. This would indicate a harmonics issue, no?
No, it shouldn't.

You said it hums with the TV "off" too, but have you tried unplugging the TV's power cord all together to make sure it was really off?

If with power cord unplugged and the hum persists then we odd to look for something else.

Aside from the TV, have you added any other devices, including appliances prior to noticing the hum?
 
M

mgood

Enthusiast
First test was to replace the Anthem altogether. My local had a Denon X4500H demo unit that I've borrowed. No hum at all. Dead silent. The Denon is scorching hot though, but this seems to be normal with these units.

Will set up the Anthem in another room to see what results I get.
 
lovinthehd

lovinthehd

Audioholic Slumlord
First test was to replace the Anthem altogether. My local had a Denon X4500H demo unit that I've borrowed. No hum at all. Dead silent. The Denon is scorching hot though, but this seems to be normal with these units.

Will set up the Anthem in another room to see what results I get.
What are you doing to get it scorching hot?! Can always add cooling....
 
M

mgood

Enthusiast
What are you doing to get it scorching hot?! Can always add cooling....
Scorching hot might be a slight exaggeration. But it definitely runs hotter than the Anthem. My speakers are 4 ohms with 80-something sensitivity, which I’m sure doesn’t help.

I’ve seen people add cooling fans to the Denon and Marantz units. Might try this approach.
 
lovinthehd

lovinthehd

Audioholic Slumlord
Scorching hot might be a slight exaggeration. But it definitely runs hotter than the Anthem. My speakers are 4 ohms with 80-something sensitivity, which I’m sure doesn’t help.

I’ve seen people add cooling fans to the Denon and Marantz units. Might try this approach.
Coolerguys.com and acinfinity.com have some good choices.
 
P

PENG

Audioholic Overlord
Scorching hot might be a slight exaggeration. But it definitely runs hotter than the Anthem. My speakers are 4 ohms with 80-something sensitivity, which I’m sure doesn’t help.

I’ve seen people add cooling fans to the Denon and Marantz units. Might try this approach.
Before you push it to high volume, like pass -15, be sure to put a fan or two on top. Rule of thumb for driving 4 ohm speaker safely is, if the amp is rated 100 W, treat as a 50 W amp when used for 4 ohms in order to be on the safe side. You can use the impedance setting for 4 ohm but you may notice a drop in dynamics. It all depends on your actual power need.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
First test was to replace the Anthem altogether. My local had a Denon X4500H demo unit that I've borrowed. No hum at all. Dead silent. The Denon is scorching hot though, but this seems to be normal with these units.

Will set up the Anthem in another room to see what results I get.
Get fans or try a Yamaha if your dealer has a demo. Yamaha operates much cooler.
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
Before you push it to high volume, like pass -15, be sure to put a fan or two on top. Rule of thumb for driving 4 ohm speaker safely is, if the amp is rated 100 W, treat as a 50 W amp when used for 4 ohms in order to be on the safe side. You can use the impedance setting for 4 ohm but you may notice a drop in dynamics. It all depends on your actual power need.
Doesn't the Power Saver or Economy mode also lower the operating temperature?
 
P

PENG

Audioholic Overlord
Doesn't the Power Saver or Economy mode also lower the operating temperature?
Yes eco would it, but also limit the output voltage. You can't get something for nothing, so ext fan is the most practical solution. It is better than paying for the otherwise much heavier heatsinks and power supply that may not be put to good use for a lot of users.
 
M

mgood

Enthusiast
First test was to replace the Anthem altogether. My local had a Denon X4500H demo unit that I've borrowed. No hum at all. Dead silent. The Denon is scorching hot though, but this seems to be normal with these units.

Will set up the Anthem in another room to see what results I get.
Correction: The Denon actually emits a very faint hum when I turn on the TV which can only be heard within 0.5 meters of the unit. The noise floor in my room is quite high when it's windy, and western Norway is windy most of the time, so it took me a while to notice.

I would probably think nothing of it if I hadn't had problems with the Anthem. Could the "noisy" power potentially hurt the el-core transformer in the Denon?

Thinking about borrowing another TV to test, but that is quite an endeavor...
 
P

PENG

Audioholic Overlord
Correction: The Denon actually emits a very faint hum when I turn on the TV which can only be heard within 0.5 meters of the unit. The noise floor in my room is quite high when it's windy, and western Norway is windy most of the time, so it took me a while to notice.

I would probably think nothing of it if I hadn't had problems with the Anthem. Could the "noisy" power potentially hurt the el-core transformer in the Denon?

Thinking about borrowing another TV to test, but that is quite an endeavor...
What's the frequency of the faint hum, and is it a sustained hum?

Also, can you please answer the following questions I asked in my earlier post?

"You said it hums with the TV "off" too, but have you tried unplugging the TV's power cord all together to make sure it was really off?

If with power cord unplugged and the hum persists then we odd to look for something else."

It does sound to me the Denon would only emit the faint noise when the TV is turned on, but not when it is off, even with the TV power cord still connected right?

EMI/RFI shouldn't cause transformer hum to increase so dramatically, so if you are sure the hum is from the unit/transformer itself, not from the speakers, then I would still think it is due to EMI/RFI from the TV, though I would not say it is 100% certainty..
 
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P

PENG

Audioholic Overlord
mgood:

Just so you know why I would like to be sure if the hum you are getting is from the transformer itself, here's something you should read about transformer hum, the linked article is about larger power transformers but the same principles apply to smaller power transformers used in audio amplifiers as well.


"Transformer noise cannot be eliminated. It can, however, be reduced through proper design and assembly, and/or masked through proper consideration of the installation.
The basic cause of transformer noise is magnetostriction: the expansion and contraction of the iron core (laminations) due to the magnetic effect of alternation current flowing through the transformer coils. This produces an audible hum. Magnetostriction may be partially controlled by the transformer design, but it cannot be totally eliminated.

The fundamental sound frequency is twice the power line operating frequency of the transformer (i.e., a 50 Hz transformer produces sound at 100 Hz and a 60 Hz transformer produces sound at 120 Hz). In addition to the fundamental frequency, harmonics are also produced."

So while it is easy to understand how/why radio frequency interference can cause hum and other noises in the more sensitive part of the receiver/amp, get amplified and produce such unwanted noises through your speaker, it would be harder to imagine such interference could be so strong as to cause the transformer itself to contract/expand, i.e. vibrate so much more to increase the hum noise by so much. Transformers transform the applied voltage to a higher or lower level, but they are not amplifiers. The reason why I think it is important to first figure out the nature of the cause, whether it is originated from that TV or not, is so it may help finding the right solution.
 
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