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DCC sound-electrical interference?


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I have a Loksound XL V5 loaded with the amazing Legoman Deltic sound project. As soon as F1 is triggered to start the sounds a high pitched whistle can be heard (similar to the temporary tinnitus you get after a loud concert - or perhaps after walking through an engine room!!). I've sent the chip back and Charlie from DC kits has confirmed that there is nothing wrong with the chip and I'm feeling guilty that it's been back to him twice (and thanks for the amazing service Charlie). 

 

The sounds can be heard in the videos below - one with master volume at 1 and the other with master volume at 255 (default). The high pitched whistle is there no matter what the volume. I've tried everything-including a non neon light fitted four board in case the light was somehow interfering, trying different sockets round the house, removing the booster, just wiring straight from Powercab to chip (i.e. no loco in the way) etc.

 

Interestingly if I pull out the mains plug to the NCE Powercab the high pitched whistle goes as the stat alive capacitors keep the engine sounds going for a few minutes, so I can only presume that its a mains interference issue or an issue with the Powercab?

 

My OO gauge Loksound Legoman Deltic doesn't do this, nor do any of my other OO or O gauge sound fitted locos and I don't really want to give up on the Powercab as its such a great system but I don't have another DCC system here to try out.

 

I'm utterly baffled and wondered if anyone has any ideas? The high pitched whistle drives you crazy after a few minutes!!

 

Thanks, Phil 

 

 

 

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9 minutes ago, Chrisr40 said:

Hi , if the chip is tested as okay have you tried a different speaker ? 

Yes I've tried several different speakers and unfortunately get the same result. It's very, very weird. It would be good to try a different DCC system to see if its the NCE Powercab, but unfortunately I don't have access to another system. What I can't fathom is why the OO gauge Legoman Deltic Loksound chip works fine but the XL version has this issue. Just doesn't make sense? 

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46 minutes ago, RAF96 said:

Have you tried the setup in a decoder test rig to eliminate the loco.

The sounds on the video are straight from DCC system to chip, so no loco in the circuit. Charlie at DC kits has also had it on his tester with no issue. I can only think it must be some weird issue with the NCE Powercab but as above, why the OO Legoman Deltic chip doesn't do this, nor any of my other O gauge sound chips only deepens the mystery. 

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7 hours ago, philiprporter said:

The sounds on the video are straight from DCC system to chip, so no loco in the circuit. Charlie at DC kits has also had it on his tester with no issue. I can only think it must be some weird issue with the NCE Powercab but as above, why the OO Legoman Deltic chip doesn't do this, nor any of my other O gauge sound chips only deepens the mystery. 

Still thinking about this ??  Charlie

 

Are all other functions off, as I have just read this:-

 

This may not be relevant, but the NCE procab has no visual indication that any function above 6 is on or off. You get a visual on F1 thru F6.

 

F7 and F8 are readily visible and accessible on the NCE Powercab so easy to check if they have been left on.  Pressing the EXPN button at the bottom of the handset displays function no’s that are 'on'. 

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13 hours ago, charliepetty said:

Still thinking about this ??  Charlie

 

Are all other functions off, as I have just read this:-

 

This may not be relevant, but the NCE procab has no visual indication that any function above 6 is on or off. You get a visual on F1 thru F6.

 

F7 and F8 are readily visible and accessible on the NCE Powercab so easy to check if they have been left on.  Pressing the EXPN button at the bottom of the handset displays function no’s that are 'on'. 

Hi Charlie all functions are off on the Powercab except F1. I really don't know what else to try except a different DCC system. If anyone here lives in Hertfordshire/Bedfordshire and has a DCC system that isn't NCE and is happy for me to pop over please let me know!! 

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Philip,

 

As you say, definitely a strange one this, but in my opinion it must be related to the Powercab as the chips didn't do it when tested on Charlie's system, or when you pulled the mains plug. I suspect there may be some mains-borne interference on your supply. Daft as it sounds, and just for investigation purposes, try plugging the Powercab into a mains socket on a different output from your consumer unit (eg the garage or upstairs if it's normally downstairs or visa-versa) or even next door or at a pal's house. You could also try an interference filter. You can get these style ones that clip onto the cable, just buy one big enough to fit (they have no direct connection to the supply). You can also buy mains extension leads with filters.

 

https://uk.rs-online.com/web/p/ferrite-sleeves/7740632?cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Passive_Components_Whoop-_-Ferrite+Sleeves_Whoop-_-7740632&matchtype=&pla-475331977096&gclid=Cj0KCQjwqfz6BRD8ARIsAIXQCf0D9s7VYvYSS3ZasZVN2mDzsKiGDA_f-aDS155IWwRL00zcLKrmXDoaAhLZEALw_wcB&gclsrc=aw.ds

 

If you do fix this, please let us know.

 

Bif

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10 minutes ago, legomanbiffo said:

Philip,

 

As you say, definitely a strange one this, but in my opinion it must be related to the Powercab as the chips didn't do it when tested on Charlie's system, or when you pulled the mains plug. I suspect there may be some mains-borne interference on your supply. Daft as it sounds, and just for investigation purposes, try plugging the Powercab into a mains socket on a different output from your consumer unit (eg the garage or upstairs if it's normally downstairs or visa-versa) or even next door or at a pal's house. You could also try an interference filter. You can get these style ones that clip onto the cable, just buy one big enough to fit (they have no direct connection to the supply). You can also buy mains extension leads with filters.

 

https://uk.rs-online.com/web/p/ferrite-sleeves/7740632?cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Passive_Components_Whoop-_-Ferrite+Sleeves_Whoop-_-7740632&matchtype=&pla-475331977096&gclid=Cj0KCQjwqfz6BRD8ARIsAIXQCf0D9s7VYvYSS3ZasZVN2mDzsKiGDA_f-aDS155IWwRL00zcLKrmXDoaAhLZEALw_wcB&gclsrc=aw.ds

 

If you do fix this, please let us know.

 

Bif

Thanks Bif - really helpful suggestions and thanks also to Charlie who has been a star (and I'm still feeling guilty about sending back two perfectly good chips for him to test when clearly it looks like the problem is at my end). I will go belts and braces and fit the ferrite style filter and a filtered mains lead assuming the garage circuit or a.n.other supply doesn't solve it. 

 

Yes will definitely post the outcome here if I can solve it - your O gauge Deltic project sounds so amazing that I have to get this sorted one way or the other! 

 

All the best, Phil. 

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I was wondering that too. If a replacement it could be that the filtering is not present (very common on cloned CE marked kit)  and the switching frequency of the PSU is getting out on the power leads. Although the tone sounds about 10Khz, and usually 20Khz is common on SMPSU's.  A ferrite on the output lead may cure that but it needs to be the right material mix for the frequency involved. A lot of the clip on ones usually shown are only effective from about 10Mhz upwards.

 

As the tone sounds around 10Khz,  is it the DCC switching frequency being  picked up? What is CV9 set to? It's the Motor PWM frequency in multiples of 1Khz. If it's set to 10 (10Khz), you may be able to increase it so it's not audible, if that is in fact the problem.

 

Usual disclaimers.

 

Rob

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14 hours ago, mezzoman253 said:

I was wondering that too. If a replacement it could be that the filtering is not present (very common on cloned CE marked kit)  and the switching frequency of the PSU is getting out on the power leads. Although the tone sounds about 10Khz, and usually 20Khz is common on SMPSU's.  A ferrite on the output lead may cure that but it needs to be the right material mix for the frequency involved. A lot of the clip on ones usually shown are only effective from about 10Mhz upwards.

 

As the tone sounds around 10Khz,  is it the DCC switching frequency being  picked up? What is CV9 set to? It's the Motor PWM frequency in multiples of 1Khz. If it's set to 10 (10Khz), you may be able to increase it so it's not audible, if that is in fact the problem.

 

Usual disclaimers.

 

Rob

Many thanks Rob and Chris that's very useful and interesting. I'm using the power supply that  came with the NCE Powercab (I have a Tam Valley booster but I'm not using it here) and given that the high pitched noise stops when the mains PSU is removed (the on-board stay alives keep the sound going) its almost certainly that the PSU or mains supply is where the issue lies. I've got a filtered 4 board arriving soon so will try that and also look at the ferrite sleeves that Bif mentioned. If it is the PSU then I'm hoping that may be a relatively easy fix. 

 

I've tried a different circuit in the house (garage circuit which is separate from the sockets in the house) and that didn't remove the noise so it's going to work today for a try there. What my colleagues will think when the Deltic noises start is another matter!! 

 

Its frustrating but also rather interesting trying to get to the bottom of it!!! 

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A long while back I was looking at cross talk between loco decoders, i.e. operating one loco made another react un-commanded and a suggestion at the time was to use an AM radio set at (???? forgotten) Frequency. Wandering around the layout it was surprising the amount of interference the radio was picking up, especially from PSUs and those Power-line adaptors used to provide extended internet access through the mains wiring.

 

Sorry but I cannot recall the radio frequency nor can I find it in any of my notes.

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1 hour ago, RAF96 said:

A long while back I was looking at cross talk between loco decoders, i.e. operating one loco made another react un-commanded and a suggestion at the time was to use an AM radio set at (???? forgotten) Frequency. Wandering around the layout it was surprising the amount of interference the radio was picking up, especially from PSUs and those Power-line adaptors used to provide extended internet access through the mains wiring.

 

Sorry but I cannot recall the radio frequency nor can I find it in any of my notes.

Interesting. I have tried the DCC setup at work and same result, so this points the finger of blame ever closer at the PSU - although I will look at CV9 as Rob mentions above when I next get a break. I'm not expecting miracles from the filtered 4 board given that this looks more like a PSU rather than a mains issue, but we shall see. 

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Is there a suppression inductor left in circuit between the pickups and the decoder? This will create an awful lot of magnetic interference, and especially if it is near to the speaker audible noise while the loco is on DCC.

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7 minutes ago, Suzie said:

Is there a suppression inductor left in circuit between the pickups and the decoder? This will create an awful lot of magnetic interference, and especially if it is near to the speaker audible noise while the loco is on DCC.

Thanks for the message - no the decoder has been removed from the loco (where it made the same noise) and is just running on the bench now with direct wiring from the DCC system. Cheers, Phil. 

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On 15/09/2020 at 09:53, RAF96 said:

A long while back I was looking at cross talk between loco decoders, i.e. operating one loco made another react un-commanded and a suggestion at the time was to use an AM radio set at (???? forgotten) Frequency. Wandering around the layout it was surprising the amount of interference the radio was picking up, especially from PSUs and those Power-line adaptors used to provide extended internet access through the mains wiring.

 

Sorry but I cannot recall the radio frequency nor can I find it in any of my notes.

You'd want to be on LW, as the fundamental frequencies would be 10-50Khz, even then you'll probably be picking up harmonics of those at broadcast LW.

 

Unfortunately the mains itself is now polluted so much by PLT,  LED lighting, and cheap SMPSU, to name but a few. 

 

You can only do so much to clean it up. Mainly getting your own house in order with filters and ferrites liberally spread on the mains and output leads.

 

These devices can radiate at frequencies up as high as 100Mhz plus. All that noise is radiated by the mains acting as an aerial. 

 

Rob

 

 

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OK today's update - no joy with the filtered 4 board as I suspected, so that only leaves the PSU as the culprit I guess? Although why this interference should only be present on this one chip is very strange. Only option left is to try a different DCC system. I've should have access to a Prodigy setup at the weekend so will see what happens with that. 

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Partial success - hooked everything up to a Gaugemaster Prodigy Advance 2 and you can still hear the high-pitched whistle, but its a lot less obvious and doesn't drive you round the bend so much, as it doesn't cut through the usual DCC sound white noise so much. 

 

Then as a last test, having tried a grand total of 6 different O gauge speakers with the whistle still there on the NCC Powercab and the Prodigy , I hooked up an EM2 - no high-pitched whistle, just blissful Deltic noise! I can only assume that the extreme bass of the EM2 masks the high frequency of the high pitch whistle. 

 

So I have no idea what the conclusion to all this is, except that whatever is causing the issue is less pronounced on the Gaugemaster Prodigy as compared to the NCE Powercab and with an EM2 speaker you can't hear it at all - at least my ears can't!

 

The good news is that with a large O gauge speaker and the EM2 in the Deltic combined, the high-pitched noise is almost completely masked by the EM2, but you get the meaty volume from the O gauge speaker and the Deltic sounds wonderful. 

 

Will get a video posted up tomorrow all being well. 

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Quick video clip. Gaugemaster Prodigy 2 with EM2 and large O gauge speaker. Foam over speaker mutes the high pitched noise even more without significantly impacting overall volume.

 

OK the root cause of the issue hasn't been completely solved but this will do for me and in real life (as opposed to a mobile phone recording) it sounds great.

 

Hope this is helpful to someone. 

 

 

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And now a short video with the body on - which makes it sound even better despite a small echo effect. Just need to figure out how to make it run smoother at low speed (I read somewhere about wiring the motors in series on Heljan O gauge locos to help this?), but that can wait - for now I'm just enjoying the Napier noise!

 

So in sum total to get this sounding right it was a switch from NCE Powercab to MRC/Gaugemaster Prodigy Advanced 2 that reduced the weird high frequency noise (but didn't get rid of it completely), EM2 speaker at one end which muffles the high frequency noise even more, large O gauge speaker at the other with a foam baffle over the speaker (the passive speaker diaphragm is left uncovered) to muffle out the last bits of the high frequency noise. Legomanbiffo Deltic sound project and Loksound XL chip. Huge bass despite my poor recording - sorted. It even makes the baseboards vibrate-thats got to be a good sign!

 

https://www.youtube.com/watch?v=3JnssblBr8Y&feature=youtu.be

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