I didn't know that Brookmans Park even had a transmitter - is it not somewhat posh?
So, the latest is......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?
Credit to RS, great customer service.At least you know they will look after you, but it does sound as though you will have to give Marantz the sack and try something else.So, the latest is......
I called Richer Sounds who were really sympathetic and agreed that it didn't seem right that the new AVR was not robust to this RFI and suggested to call Marantz Customer Care (Sound United) just to see what they said about the problem. If no joy, then Richer Sounds would gladly replace the unit in case it did have a fault.
Sound United referred to the email I'd already sent them about the problem a few days prior to this call and were very surprised at the problem I was describing. Their representative referred to the fact that the SR7015 doesn't have an RF Receiver, but I explained that the issue is RFI, not some problem with a tuner (that it doesn't have). He said to try "Initializing" the AVR, sending instructions to me by email. This required pressing the "Movie" and "Music" buttons together for a short while to start the initialization. This seems to just reset the unit, so unsurprisingly, no impact on the Lyca Radio pick up.
I called Richer Sounds back and they had a replacement AVR shipped to me the next morning, which was fantastic service. Rigged it up and Lyca Radio is still loud and clear, but at least this does eliminate any possible weakness in that first unit due to out of specification components etc. On the call with Richer Sounds, they also discussed the possibility for me to exchange to a completely different brand of AVR. I have to say that this level of service is really outstanding in my opinion, but of course I would prefer to try and get the SR7015 working.
I've now sent a follow up to Sound United to explain that the initialization process hasn't worked and neither has a replacement AVR.
Ref the ferrite beads, I bought some more from Amazon which are allegedly Mix 31, which is meant to be the best for this AM frequency range. I looped the speaker cables around these additional ferrite beads (which clip / unclip) as per the image in that weblink you shared, but absolutely no difference at all. I even had 3 in series on a couple of the speaker wires, close to the AVR, but no improvement.
I haven't heard back from Arqiva who manage the transmitter station. Tried to find a general email contact for Lyca Radio, but the only email address is for advertising. I'll give that a go anyway and see if they can put me on to somebody who can help.
While trawling the web, I came across this............
I know it's intended for improving sound quality if I understand correctly, rather than severe RFI, but I've contacted them with my problem to see what they think.........Zapperators use a network of specialised, very high specification components to stably absorb RF and further reduce noise in the amplifier / speaker interface. We've found that they augment the effect of Kimber speaker cable (Russ uses them on his speakers in his main system) and in our opinion...www.russandrews.com
Credit to RS, great customer service.At least you know they will look after you, but it does sound as though you will have to give Marantz the sack and try something else.
If you are that keen to keep the Marantz, you could always move - to say Stevenage?Absolutely on the RS service; really impressed. A shame if I do have to switch that Marantz for another unit, but just hope I'm not wasting RS' time if the situation persists with another brand of AVR. Especially as Denon is typically a good option but of course they are from the same stable as Marantz. I really like the look of the Marantz SR7015 that I bought so gutted if I have to move away from it.
Thanks for that and will see if they can help.Much credit to RS of course. This is costing them money in that they'll have to sell the returned units at a discount (open box returns). But what good PR/service at the same time!
Advice about receiving TV and radio | RTIS might be worth contacting. The service is run/paid for by the BBC using out-sourced front-line staff (it was Capita in my day) but is for all broadcasters, not just the BBC.
Give them a quick rundown of the issue, where you are wrt Brookmans Park, that it's only the one frequency from the site out of four, and that you've tried certain things... Ask if they can pass you on to the RTIS (BBC) Back Office Experts for them to call you back ... they'll have the ability to talk to Arqiva direct. That may, or may not, result in a visit (Covid notwithstanding) or other filtering suggestions in an attempt to stop it happening.
But it does seem an inherent design flaw by Marantz, as
1. Only one frequency of the four broadcast is affected
2. A second sample produces identical results.
Whether Denon share the same circuits/designs, and will then may suffer the same RFI issue, is something only they can answer.
Thanks for the ideas.I would suggest you fit the ferrite beads around 1 core of the cable, not the whole thing - do both cores and both ends.
This is down purely to poor amplifier design. What's happening is that the RF signal comes into the amplifier via the speaker leads, is partially demodulated by the amplifier circuitry, mixed with the audio signal from the earlier stages of amplification and re-broadcast or amplified out to the speakers.
You could try a low pass filter designed for mains inputs - but actually use it for your speaker cabling. This: RSAL-2003W | TDK-Lambda Power Line Filter, Noise Filter for use with Power Supply | RS Components is one such device and provides much better performance than just ferrite beads. It shouldn't affect audio frequencies, but you would need to test this, as they are not designed for this application.
Interesting update. It kind of supports your earlier observation that while a unit might achieve a certain specified standard, it doesn't mean that's it 's going to be robust enough in all circumstances, only the most commonly expected ones.Thanks for the ongoing replies and ideas, which I'll look into for sure. As an update on my further investigations / trials...............
1) Response from Marantz Customer Care:
" The relevant department Our products are CE proved and apply to all necessary standards. This is part of the approval for every product we bring into the market. We would suggest you swap out the speaker cables in case they may be acting as additional antennas. Failing that then please refer the unit back to the retailer or dealer where you originally purchased it from".
Not an unreasonable point about CE proved, but as I know from my automotive work, that doesn't mean it will be fine in all (reasonable) applications.
2) Response from Russ Andrews (ref potential use of their 'Zapperator' product:
"I don’t know whether it’s solely part of the amplifier’s internal circuitry that’s unfortunately tuned in to the radio station or a combination of the new amp and long speaker cable unintentionally creating a large antenna. I’m not sure which of our products will help but out of them I’d recommend you try a mains Zapperator or a Silencer under our money back guarantee but I don’t think they’re the products for this specific problem."
It was a long shot, but a kind and frank response.
3) Arqiva / Lyca Radio Response:
If you'll pardon the pun, radio silence still........
4) Installation Investigation:
It does seem that the noise volume reduces when I have the 2 surround Speakers disconnected and then eliminated completely when I have the 2 front speakers disconnected as well (so only the centre speaker connected). Note the centre speaker has a very short cable as it's close to the amp.
I've disconnected all 4 of surround speakers, then taken one off the wall and attached it to one of the AVR speaker outputs with a new piece of cable close to the AVR (i.e., not using the existing cable buried in the walls). Unfortuantely, I could hear the interference again, so my gut feel is that there is something in the SR7015 which picks up the 1458AM broadcast, regardless of my speaker installation (as suggested). Of course, there still may be an influence from the speaker cables, but I'm not convinced it's the main cause.
I'll definitely keep trying to make this work, so thanks for the recent suggestions and let you know how I get on.
I really wouldn't worry about power handling. The 3a is a continuous rating and music or movies won't get anywhere near that level of power output.Those filters are only rated at 3A (tho RS also stock the 6A version for the same price). They also present a resistance so some power loss in them is inevitable.
I^2 R = Power. Speakers at 8 ohms nominal.
3 A has a max rating of 72 W (half that if 4 ohm speakers).
Mind you most audio isn't full RMS current, so the filters might not overheat?
@noiseboy72 I also, looking at the circuit diagram, wonder if the case needs earthing to work properly? There's another version made in the range with no earth (low leakage).
As I've said this isn't my field of expertise; I have a little knowledge, but not expert!
Have you contacted the RIS directly as I suggested?
I admire the perseverance but in view of the fact an Onkyo on the same wires never gave this issue... I'd look for another brand of AVR in your precise situation (location).
The TDK Noise Filters have just arrived, so I'll try and rig them up a bit later.
The RTIS unfortunately are not taking telephone calls due to COVID andd no email address available (there is a postal address, but if they aren't taking calls, I am not sure if anybody would be there to pick up a letter). Contact Us | RTIS
So, I called OFCOM on 02079813131 and was transferred through to their "Interference Team". The lady I spoke to was as helpful as she could be, but felt that as the interference was not 'interrupting' the listening of a radio broadcast, but impacting on other things, it was outside of their remit. She did offer to speak to a supervisor to confirm this and call me back. Good as gold, she did call me and confirmed that this type of interference was outside of their scope, but suggested calling RTIS......
Anyway, I have discussed RFI from the transmitter with a couple of neighbours and some interesting stories..................
1) A family has just had some new Miele appliances with touchscreens fitted. Specifically, the touch screens on the ovens wouldn't function correctly. Miele sent engineers out who modified the connections to the mains supply (earthing etc.), but no joy. Their HQ in Germany then asked if she lived near a radio transmitter as they had experienced a similar issue in Germany at a house that was near one......She has been able to reach somebody at Arqiva who confirmed the radio frequencies being transmitted (which we know) and she has forwarded these to Miele. Miele requested this information as they want to make a countermeasure for it and test it with her ovens...... Hmmmmmmm, a bit different to Marantz's reaction....(I know, you buy cheap, you buy twice....).
2) My direct neighbour has told me that when he moved here in 2001, they could hear Indian music playing through some of the radiators in the house (!). He said had issues with his BT phone line, which BT solved by coming out and changing the connection in their main socket. He says though, that they do have issues with the operation of any 'touch control' items, such as bedside lamps......
3) ...... which led me to question something that I thought was just a fault in my home with the electrics. Bought some touch control bedside lamps and one of the two would only function by touch intermittently, but the other one in a different mains socket would not work at all. Replaced the non functioning one with a new one and no difference. We also have issued where if a mobile phone is plugged into the mains, the capacitive touch screen works erratically. The guy who fitted the CCTV system couldn't use the scratch pad on his laptop.....I unplugged the lap top from the mains and it worked fine......). I always assumed those issues were down to the house electrics, but now I'm wondering if it's that bloody transmitter!
Anyway, let's try those TDK RFI filters...........
Try and wire the suppressor as close to the amplifier as possible. See if that makes any difference. All you are doing by putting the suppression there is effectively terminating the end of the aerial cable.
I admire your persistence, but I would give up and try a different AVR! There's obviously something inherent with the Marantz, and the speaker cables are probably just aggravating it.View attachment 1462517
I wired it in as close to the AVR as possible, with minimal speaker wire length to the speaker and still have Lyca FM coming through when the remaining 4 speakers are also attached. Am I right to assume then that even if the other 4 (original) speaker wires are acting as antennae, this filter is not actually filtering the interference (as outputted by the AVR)? My point being, that even if I added one of these to each of the AVR's 5 speaker outputs, it wouldn't make any difference (given that this one speaker is still outputting the interference when the other original speaker wires are attached to the AVR). Thanks.
PS: I'm fairly sure the ferrite beads are doing absolutely nothing!