Marantz SR7015 Radio Interference from Radio Station

CaptainJames

Well-known Member
I suspect that the AVR is not "faulty" as such, but just not constructed robustly enough to be used in it's current location. Or in other words, in 99% of "normal" locations (no offence to the good people of Brookmans Park) it would probably function without problem.

Not saying that it shouldn't work as well close to a transmitter, as other manufacturers have proved that it's perfectly possible.
 

jwlawler

Active Member
I eavesdropped on the development labs of both Onkyo and Marantz a while ago and I heard these conversations.

Onkyo

Engineer 1: You know some of our customers might live just a few hundred metres from a powerful AM radio transmitter.

Engineer 2: Okay, let's ensure that our new AVR won't pick up interference.

Marantz

Engineer 1: What would happen if a customer lives just a few hundred metres from a powerful AM radio transmitter.

Engineer 2: No one is going to do that are they? Let's not waste money designing for that.

More seriously. I think that it just good luck that the Onkyo coped and bad luck that the Marantz doesn't. It could even be that each would sometimes be okay and sometimes not depending on location and orientation. It could be a difference in the orientation of some of the internal components or a different choice of components.
 

Dem

Active Member
I suspect that the AVR is not "faulty" as such, but just not constructed robustly enough to be used in it's current location. Or in other words, in 99% of "normal" locations (no offence to the good people of Brookmans Park) it would probably function without problem.

Not saying that it shouldn't work as well close to a transmitter, as other manufacturers have proved that it's perfectly possible.
Absolutely agree with that, in as much as it meets Marantz's specifications, but clearly not everyone in the user population. That's the point about what is deemed 'close' to a transmitter? However, nonetheless, when they sell it, they don't mention that it will likely have difficulties in certain areas / within 'x' metres of 'y' problem source. Again using the automotive world, there are sometimes EMC problems that occur in certain places which despite best efforts to engineer for, can never be foreseen. Doesn't make that customer any happier though and the product is deemed not robust enough......
 

Dem

Active Member
I eavesdropped on the development labs of both Onkyo and Marantz a while ago and I heard these conversations.

Onkyo

Engineer 1: You know some of our customers might live just a few hundred metres from a powerful AM radio transmitter.

Engineer 2: Okay, let's ensure that our new AVR won't pick up interference.

Marantz

Engineer 1: What would happen if a customer lives just a few hundred metres from a powerful AM radio transmitter.

Engineer 2: No one is going to do that are they? Let's not waste money designing for that.

More seriously. I think that it just good luck that the Onkyo coped and bad luck that the Marantz doesn't. It could even be that each would sometimes be okay and sometimes not depending on location and orientation. It could be a difference in the orientation of some of the internal components or a different choice of components.
Well, it's bad luck or bad / less robust design.......
 

Dem

Active Member
Yes that's the ground terminal I was suggesting you use.

Metalwork on a double-insulated item is not connected to a proper ground/earth is it? So temporarily connecting it to the home earth may prove (or disprove) something wrt the screening effect with a 'proper earth'?

Only if it 'fixes' the pickup issue will it need considering as a permanent solution. Even then the dreaded earth loop hum may not happen.

My gut is saying that the AM transmitter is getting in at around the DSP-analogue output stage, or power amp inputs... especially if Lyca is a fixed level as I'm inferring from the first post description.
So something is getting past the chassis/case screening and into the box?
It may be the AVR is faulty (mis-assembled) or just poorly designed and not immune enough to the legal transmitted signal?

The 1458 kHz transmitter wavelength is roughly 205 metres, 1/2 wave 102 m, 1/4 51 m so bits of wire need to be long to be a proper match (or coils of wire around a magnetic core as in AM radios).
Thanks again for the insight. I have played around with the AVR more today with the following observations......

- I attached a wire from that ground terminal on the rear of the AVR to one of the mains faceplate screws and............Radio Lyca got louder! :) So, I canned that idea.

- I then moved the AVR to the original part of the house (room next door) with the centre speaker attached and could not hear any interference. I then put the AVR and centre speaker back into it's intended location in the extension, but this time could not hear any interference. However.........

- As I started to connect each of the 4 speakers which are mounted high up on the walls in the corner of the room, Radio Lyca became louder and louder through the centre speaker (I could hear this as it's the one closest to my ear while I'm plugging the other speaker cables into the back of the AVR). I then plugged / unplugged the various speakers and in summary, it seems that when I only attach one speaker, the interference from the radio station is barely perceptible, but just about there (certainly, not something that would bother me). It's low enough that I clearly didn't pick this up when first playing around with it and only having that centre speaker connected. Disconnecting that centre speaker then attaching any of the others, gives the same effect at those speakers (i.e. you can just about hear the radio station with your ear close to the speaker). However, it seems that re-attaching each speaker has a combined effect to the point that once all five are attached, Radio Lyca is playing fairly strong through all of them (but I hear it most through that centre speaker as it's the closest to me I guess). You have a fairly perceptible step up in volume as you add each speaker in turn to the AVR.

I guess that means that the speaker cables are acting as antenna as first considered in this thread. However, I can't help but compare with the old Onkyo that didn't suffer from this as being more robust.

I have those ferrite core / clamps which arrived from Amazon today, but not sure if they're worth bothering with?

Thanks,

Dem.
 

jwlawler

Active Member
Well, it's bad luck or bad / less robust design.......

A couple of possibilities are:

It didn't occur to them that anyone would live so close to a transmitter.

It occurred to them but they thought that they would not lose or upset enough customers to justify the cost.
 

jwlawler

Active Member
Thanks again for the insight. I have played around with the AVR more today with the following observations......

- I attached a wire from that ground terminal on the rear of the AVR to one of the mains faceplate screws and............Radio Lyca got louder! :) So, I canned that idea.

- I then moved the AVR to the original part of the house (room next door) with the centre speaker attached and could not hear any interference. I then put the AVR and centre speaker back into it's intended location in the extension, but this time could not hear any interference. However.........

- As I started to connect each of the 4 speakers which are mounted high up on the walls in the corner of the room, Radio Lyca became louder and louder through the centre speaker (I could hear this as it's the one closest to my ear while I'm plugging the other speaker cables into the back of the AVR). I then plugged / unplugged the various speakers and in summary, it seems that when I only attach one speaker, the interference from the radio station is barely perceptible, but just about there (certainly, not something that would bother me). It's low enough that I clearly didn't pick this up when first playing around with it and only having that centre speaker connected. Disconnecting that centre speaker then attaching any of the others, gives the same effect at those speakers (i.e. you can just about hear the radio station with your ear close to the speaker). However, it seems that re-attaching each speaker has a combined effect to the point that once all five are attached, Radio Lyca is playing fairly strong through all of them (but I hear it most through that centre speaker as it's the closest to me I guess). You have a fairly perceptible step up in volume as you add each speaker in turn to the AVR.

I guess that means that the speaker cables are acting as antenna as first considered in this thread. However, I can't help but compare with the old Onkyo that didn't suffer from this as being more robust.

I have those ferrite core / clamps which arrived from Amazon today, but not sure if they're worth bothering with?

Thanks,

Dem.

Some interesting findings.

We should have realised that the earth connection might make it worse. Long ago, radios would often have an earth connection to improve the reception of radio signals. It was worth trying though.

So, it seems that your speaker cables are acting as antennae. My next idea is to look for some shielded speaker. I don't know how easy it is get as it is not often required.

Why the Marantz and not the Onkyo? We are back to guesswork. Just a quirk in their circuit designs. One is affected by interference coming into the speaker terminals but the other isn't.

A tiny capacitor across the speaker terminals might help. A capacitor conducts high frequencies easily but low frequencies poorly. With the correct value, it would damp the radio frequency but have no effect on the audio frequencies. Now, the question is what is a suitable value? It should be tiny so that audio is not affected. Maybe just a pF. Do you use Stack Exchange? Its Electrical Engineering site might be able to advise.
 

Dem

Active Member
Some interesting findings.

We should have realised that the earth connection might make it worse. Long ago, radios would often have an earth connection to improve the reception of radio signals. It was worth trying though.

So, it seems that your speaker cables are acting as antennae. My next idea is to look for some shielded speaker. I don't know how easy it is get as it is not often required.

Why the Marantz and not the Onkyo? We are back to guesswork. Just a quirk in their circuit designs. One is affected by interference coming into the speaker terminals but the other isn't.

A tiny capacitor across the speaker terminals might help. A capacitor conducts high frequencies easily but low frequencies poorly. With the correct value, it would damp the radio frequency but have no effect on the audio frequencies. Now, the question is what is a suitable value? It should be tiny so that audio is not affected. Maybe just a pF. Do you use Stack Exchange? Its Electrical Engineering site might be able to advise.
Thanks. I did think about the capacitor idea, but all sounds a bit Heath Robinson having spent out on a decent spec AVR! I might as well give those snap fit ferrite cores a whirl on the speaker cables at the AVR end.
 

jwlawler

Active Member
Thanks. I did think about the capacitor idea, but all sounds a bit Heath Robinson having spent out on a decent spec AVR! I might as well give those snap fit ferrite cores a whirl on the speaker cables at the AVR end.

My other choice would be shielded speaker cable. I've never looked before but shielded speaker cable is a thing. Normally, I'd say that it was for cranks but you may be a special case. I am not particularly recommending this product, it's just my first hit. It's not stupidly expensive and should be safer than either my capacitor or your ferrite coil.

 

Dem

Active Member
My other choice would be shielded speaker cable. I've never looked before but shielded speaker cable is a thing. Normally, I'd say that it was for cranks but you may be a special case. I am not particularly recommending this product, it's just my first hit. It's not stupidly expensive and should be safer than either my capacitor or your ferrite coil.

Yes, thanks for that idea. Only problem is of course that the four speakers have their cables buried in the walls when the extension was built. I'm sure it would be a good solution, but as you can imagine, last thing I really want to do.
 

jwlawler

Active Member
Yes, thanks for that idea. Only problem is of course that the four speakers have their cables buried in the walls when the extension was built. I'm sure it would be a good solution, but as you can imagine, last thing I really want to do.

Oh yes, I forgot that you said that. Well, that's what a hammer and chisel is for.
 

CaptainJames

Well-known Member
Thanks again for the insight. I have played around with the AVR more today with the following observations......

- I attached a wire from that ground terminal on the rear of the AVR to one of the mains faceplate screws and............Radio Lyca got louder! :) So, I canned that idea.

- I then moved the AVR to the original part of the house (room next door) with the centre speaker attached and could not hear any interference. I then put the AVR and centre speaker back into it's intended location in the extension, but this time could not hear any interference. However.........

- As I started to connect each of the 4 speakers which are mounted high up on the walls in the corner of the room, Radio Lyca became louder and louder through the centre speaker (I could hear this as it's the one closest to my ear while I'm plugging the other speaker cables into the back of the AVR). I then plugged / unplugged the various speakers and in summary, it seems that when I only attach one speaker, the interference from the radio station is barely perceptible, but just about there (certainly, not something that would bother me). It's low enough that I clearly didn't pick this up when first playing around with it and only having that centre speaker connected. Disconnecting that centre speaker then attaching any of the others, gives the same effect at those speakers (i.e. you can just about hear the radio station with your ear close to the speaker). However, it seems that re-attaching each speaker has a combined effect to the point that once all five are attached, Radio Lyca is playing fairly strong through all of them (but I hear it most through that centre speaker as it's the closest to me I guess). You have a fairly perceptible step up in volume as you add each speaker in turn to the AVR.

I guess that means that the speaker cables are acting as antenna as first considered in this thread. However, I can't help but compare with the old Onkyo that didn't suffer from this as being more robust.

I have those ferrite core / clamps which arrived from Amazon today, but not sure if they're worth bothering with?

Thanks,

Dem.
Did I mention it could be the speaker cables? ;):smoke:
 

jwlawler

Active Member
Did I mention it could be the speaker cables? ;):smoke:

A surprising (to me) result but the evidence is strong now. Obviously theoretically possible but I have never heard of a problem like this before. On the other, I have never heard of someone using HiFi so close to a powerful AM transmitter. If you want weird interference than this is probably the way to get it. Even better might be to live near the Radio 4 LW in Droitwich. It is nearish me but much more than 400m.

Now my Mum lives close to a nuclear power plant. So, she has the problem of stray neutrons destroying her electronics.
 

CaptainJames

Well-known Member
I have never heard of someone using HiFi so close to a powerful AM transmitter. If you want weird interference than this is probably the way to get it.

This.

Funnily enough, I haven't listened to an AM station since the 80's - surprised they haven't all been switched off by now.

Now my Mum lives close to a nuclear power plant. So, she has the problem of stray neutrons destroying her electronics.
:eek:
 

jwlawler

Active Member
This.

Funnily enough, I haven't listened to an AM station since the 80's - surprised they haven't all been switched off by now.


:eek:

Quoting went a bit funny.

I was aware that AM transmissions were still there. Just a little while ago, I found and played with my father's first portable radio which was MW/LW AM only. I think that there are still so many old radios out there that too many people would be upset at their loss. There is pressure to shut down FM as there are lots of other potential use for their frequency band. The pressure to stop AM is probably lower as there is much less interest in the MW and LW frequency bands. AM might outlive FM. It might even outlive DAB.

Mum does live near a nuclear power plant but does not really suffer from stray neutrons.
 

CaptainJames

Well-known Member

jwlawler

Active Member
But can you be sure? :eek: ;)

Well, she has got to 94 so, if anything, the stray radiation may be helping. Her TV is also still working after more than a decade. Plenty of things go wrong in her house but it is hard to blame the nuclear power plant.
 

CaptainJames

Well-known Member
Well, she has got to 94 so, if anything, the stray radiation may be helping. Her TV is also still working after more than a decade. Plenty of things go wrong in her house but it is hard to blame the nuclear power plant.
Wow, you should offer her up to use in a advert for nuclear power - 94! :thumbsup:
 

gibbsy

Moderator
Well, she has got to 94 so, if anything, the stray radiation may be helping. Her TV is also still working after more than a decade. Plenty of things go wrong in her house but it is hard to blame the nuclear power plant.
Her favourite meal is Fission Chips.

94 is a good age. Make sure she stays safe in these troubled times.:smashin:
 

jwlawler

Active Member
Her favourite meal is Fission Chips.

94 is a good age. Make sure she stays safe in these troubled times.:smashin:

Yes, she loves that.

Unfortunately, I can't help much as I am far away. Luckily my sister is nearby and in a bubble with her. She is wondering why I don't come to visit much at the moment.
 

Dem

Active Member
Well, I tried those ferrite cores on the speaker wires that I bought from Amazon.Made in China so in fairness, progeny is questionable, but did absolutely sod all.... I even looped the wires a bit as suggested somewhere, but Radio Lyca still nice and strong 💪
P_20210202_173838.jpg

Not heard back from my online query to Marantz yet, so I'll give Richer Sounds a call tomorrow and see what they say.
 

Dem

Active Member
A surprising (to me) result but the evidence is strong now. Obviously theoretically possible but I have never heard of a problem like this before. On the other, I have never heard of someone using HiFi so close to a powerful AM transmitter. If you want weird interference than this is probably the way to get it. Even better might be to live near the Radio 4 LW in Droitwich. It is nearish me but much more than 400m.

Now my Mum lives close to a nuclear power plant. So, she has the problem of stray neutrons destroying her electronics.
I suppose none of the other many houses around the radio transmitter would have an AVR then..... 😜😜😜 Well, maybe not a Marantz.... 🤣
 

Rodders53

Distinguished Member
The wires need to go through the ferrite cores and around then back through as a coil to have any proper effect. In fact I believe that, as pictured, they'll do absolutely nothing.
How to Use Ferrite Cores with Instrumentation | Omega has a picture to show 'how' to use them.

You may need cores that unclip/hinge open to facilitate that being done without removing the banana plugs.

NB Brookmans Park currently transmits four radio stations:
Absolute Radio 1215 kHz 62.5 kW
BBC Radio 5 Live 909 kHz 200 kW
Lyca Radio 1458 kHz 125 kW
Talk Sport 1089 kHz 400 kW

but only one of them is causing problems.

So something is 'matching' that wavelength only, or is in a location where there's a peak 'standing wave' type of reception condition at that frequency, or some components inside the unit are related to that frequency and the speaker cables just induce more signal into the unit (just as the 'signal ground' did when earthed).

Have you asked Lyca, Marantz or Richer for their view?
 

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