Author Topic: Help me identify source of interference (RFI?)  (Read 17064 times)

Offline ptjw

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Help me identify source of interference (RFI?)
« on: February 24, 2016, 14:08 »
I inherited an Audio Technica LP120 turntable recently, and I noticed a really irritating high pitched whine that would change in pitch and loudness all on its own even when the turntable is at rest i.e stationary platter, needle in the air.

sound of the interference here:
https://www.youtube.com/embed/yLSZ4UnH4Vs?wmode=opaque

This sound comes even after changing amplifiers, so I know it is definitely coming from the turntable.. it comes even when the turntable is powered off (but connected to the amp) so I can rule out a noisy power line. I'm very sure it is radio frequency (RFI) interference of some sort, and it sounds like a data transmission since it is pretty consistent in timing and frequency.

I've read many instances of turntables being sensitive enough to pick up radio frequencies in the air due to poor shielding and I've placed a handful of ferrite beads on the cables inside and outside the turntable with no luck. I was desperate enough to try wrapping aluminum foil around some cables and that actually reduced the noise a little to more tolerable levels but it is definitely still there. So since the aluminum foil works, it should be RFI (i think).

I've posted on a few forums with no luck in getting a solution, so my interest now is more of possibly identifying the source of this noise. Has anyone ever come across noise like this in Singapore? Maybe wifi, maybe alarm systems, maybe radio/TV signals that transmit signals similar to this? I'm even beginning to suspect radar (I'm located in Bukit Panjang) from a nearby base since the sound comes and goes regularly every few seconds.. but probably unlikely.

I ran the sound through the spectrum analyzer in Audacity and this is the result:

with peaks around 5300hz and 8000hz.

Anyone with experience in radio/interference know what might cause this? Thanks! :D

Offline wizardofoz

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Re: Help me identify source of interference (RFI?)
« Reply #1 on: February 24, 2016, 14:36 »
I used to get this from time to time...not just on phono input but others as well...mine had some clicking in the background too.


I think blue_starfish posted something about RFI from transmitters the other day here http://www.xtremeplace.com/yabbse/index.php?topic=219351.msg1124358#msg1124358


mine are like this...the first one you can hear my clock too...ignore that
http://www.walaneh.com/xpl/Memo1.m4a

http://www.walaneh.com/xpl/Memo2.m4a


if you search the forums quite a few people have this or similar issues...especially with phono use.


could be proximity to large powerful transmission equipment but one person found (transmat) found it coincided with lifts passing by his floor...
« Last Edit: February 24, 2016, 14:45 by wizardofoz »
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It's wonderful to behold as long as you don't let the magic smoke out.

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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #2 on: February 24, 2016, 15:01 »
thanks for replying, i listened to your recordings and they are indeed very similar to what i'm hearing on my side.. but mine is solely on the phono inputs only.. my other equipment at line levels have no issues at all and are silent.

did you fix this somehow? or do you live with it? it is quite hard to listen to vinyl at a decent volume without hearing the high pitched noise coming through to the ears.. i only recently shifted to a new BTO in bukit panjang, whereas my old place never had such a problem..

i tried it in the middle of the night once and it was still there, so i can rule out lifts causing the interference as well.. i don't stay near the top floor of my block so i'm not near the lift motors as well (if that makes sense).

really strange.. what/who is transmitting this? :D

Online jerome_the_lang

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Re: Help me identify source of interference (RFI?)
« Reply #3 on: February 24, 2016, 15:17 »
Phono cables and/or cartridge possibly picking radiation from turntable motor....

 :D


Change to anther interconnect with different RCA plugs and run them in such a way so that they do not cross path or come near to the turntable motor power supply cable.

One option is placing the phono/amp on the right side of the turntable, while the TT motor power supply cable is routed to the left.

Alternatively, change to mc cartridges which generally offer better "shielding" against radiation.
« Last Edit: February 24, 2016, 15:21 by jerome_the_lang »
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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #4 on: February 24, 2016, 15:28 »
Phono cables and/or cartridge picking radiation from turntable motor....

Change to anther interconnect with different RCA plugs and run them in such a way so that they do not cross path or come near to the turntable motor power supply cable.

One option is placing the phono/amp on the right side of the turntable, while the TT motor power supply cable is routed to the left.

Alternatively, change to mc cartridges which generally offer better "shielding" against radiation.

i left out the detail that the turntable is not even powered on at this stage; only the RCA cables are connected to the phono in on the amplifier and the turntable is not on and motor is not running, so i can rule out EMI from the motor. also, the volume of the interference is the same whether the motor is running or not.

i removed the headshell and the interference is still there, just with more noise thrown in since the connections are open and ungrounded.

so my setup is:
Turntable (AT-LP120) -> phono in Amplifier (Onkyo A-9050) -> Speakers

with no preamp in between as i performed the modification to remove the built in preamp from the turntable, so the RCA cables in the turntable are connected directly to the tonearm wires with nothing in the way.

Offline blue_starfish

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Re: Help me identify source of interference (RFI?)
« Reply #5 on: February 24, 2016, 15:58 »
I am making a wild guess here. The noise can be from the Onkyo and not just the RCA cables. After you have wrapped the RCA with foil, the noise lessened. Ground the Onkyo well, and wrap it with foil too (like a Faraday cage) and see if the noise lessens significantly. Could be the on board phono picking up.

Upper Bt Timah/ Bt Batok and Toh Tuck are bad areas to play TT due to RFI. I struggled with it for a long time and took steps to do additional grounding to all my power cords. My noise was hum and not high pitch.

Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #6 on: February 24, 2016, 16:22 »
I am making a wild guess here. The noise can be from the Onkyo and not just the RCA cables. After you have wrapped the RCA with foil, the noise lessened. Ground the Onkyo well, and wrap it with foil too (like a Faraday cage) and see if the noise lessens significantly. Could be the on board phono picking up.

Upper Bt Timah/ Bt Batok and Toh Tuck are bad areas to play TT due to RFI. I struggled with it for a long time and took steps to do additional grounding to all my power cords. My noise was hum and not high pitch.

don't think it is the Onkyo as I swapped it with a cheap China tube amp which doesn't have a phono input and used an external preamp (TCC-750) with the turntable and the high pitched noise is still there so i'm pretty sure the source is the turntable.

i used to stay in upper bukit timah and did NOT have such a problem.. only moved house last month and heard this for the first time ever and it never goes away  :-\

i ran a ground wire from the grounding lug on the Onkyo to the earth pin on the mains and it reduced the background hum and hiss but not the high pitched sound.. in fact my turntable used to sound a little buzzy like the audio recordings from wizardofoz until i grounded the Onkyo directly to the mains socket and now all the inputs are really really silent.. even the phono as from the recording i made above on youtube there is very little hiss/hum.. only the pure tone of the interference that goes EEEEEEEEEEEEEEEEEEEEEEEE... eeeeeeeeeeeeeeeee... EEEEEEEEEEEEEEEEEEEE  :D

i did try opening the tonearm and twisting the tonearm wires around but that didn't contribute anything.. maybe i should try wrapping the arm in foil as well.. not sure where on the turntable is it picking up these signals from.. i would need to find the 'antenna' and smother it in foil..


Offline Jag

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Re: Help me identify source of interference (RFI?)
« Reply #7 on: February 24, 2016, 16:40 »
Unplug your wifi router from the wall. Switch off is not enough. Need to remove it physically to ensure total electrical disconnection.
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Offline pcking

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Re: Help me identify source of interference (RFI?)
« Reply #8 on: February 24, 2016, 16:58 »
This may sound stupid but did you have the USB output from your TT connected to somewhere ?
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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #9 on: February 24, 2016, 17:03 »
Unplug your wifi router from the wall. Switch off is not enough. Need to remove it physically to ensure total electrical disconnection.

thanks for the suggestion, i have already done this though.. as it was a new house and my audio equipment was the first few things to come in i could easily turn off all the equipment in the house: lights, routers, fans, etc but the beeping is still there. i switched off everything other than the amplifier and the turntable in my house..

This may sound stupid but did you have the USB output from your TT connected to somewhere ?

i performed the mod to remove the preamp, thus there is no more USB output from the turntable, only RCA outputs which are directly connected to the tonearm wires.

thanks for all the suggestions, appreciate them as i could easily have overlooked something trivial in the process of trying to nullify this problem ;D

Offline Jag

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Re: Help me identify source of interference (RFI?)
« Reply #10 on: February 24, 2016, 17:31 »
Oh, new house. Do this:

Turn off all the circuit breakers in your home, including the lights. Keep only the MCB switched on for your TT and amp. Shutdown your phone also. Keep any electronics away from the TT, amp and speaker.

If everything else is not energized, hopefully the noise is gone. Else, perhsps the area you are living in has this RFI and the source transmitter is not within your control.
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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #11 on: February 24, 2016, 18:20 »
Oh, new house. Do this:

Turn off all the circuit breakers in your home, including the lights. Keep only the MCB switched on for your TT and amp. Shutdown your phone also. Keep any electronics away from the TT, amp and speaker.

If everything else is not energized, hopefully the noise is gone. Else, perhsps the area you are living in has this RFI and the source transmitter is not within your control.

thanks for your suggestion, also did that before  :) spent a full month troubleshooting and eliminating all possible sources from within my house which is why i concluded it has to be RFI coming from elsewhere (outside) and wondered if anyone has ever heard this before and know where it comes from.. wizardofoz's recordings sound the most similar, changing high pitched noises that come and go in a cycle of a few seconds.. basically "eeeeeeeeee... EEEEEEEEEE... *silent*... eeeeeeeeee... EEEEEEEEEE... *silent*" and keeps repeating  ;D

i used to stay near Gombak hill as well with the big radar dish up there, but no such interference when i was there.. but here in Bukit Panjang it's happening all day long.. one thing i haven't tried was wrapping the whole turntable and amp in foil.. but if i have to resort to such measures to listen to vinyl i'll just stick to CDs and digital  :P

Offline francishuang

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Re: Help me identify source of interference (RFI?)
« Reply #12 on: February 24, 2016, 18:22 »
Bukit panjang too
Bangkit area
Same problem
Tried everything for 2 yrs
It neva goes away
Gave up.

thanks for your suggestion, also did that before  :) spent a full month troubleshooting and eliminating all possible sources from within my house which is why i concluded it has to be RFI coming from elsewhere (outside) and wondered if anyone has ever heard this before and know where it comes from.. wizardofoz's recordings sound the most similar, changing high pitched noises that come and go in a cycle of a few seconds.. basically "eeeeeeeeee... EEEEEEEEEE... *silent*... eeeeeeeeee... EEEEEEEEEE... *silent*" and keeps repeating  ;D

i used to stay near Gombak hill as well with the big radar dish up there, but no such interference when i was there.. but here in Bukit Panjang it's happening all day long.. one thing i haven't tried was wrapping the whole turntable and amp in foil.. but if i have to resort to such measures to listen to vinyl i'll just stick to CDs and digital  :P
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Offline Boxerfan88

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Help me identify source of interference (RFI?)
« Reply #13 on: February 24, 2016, 18:36 »
If you disconnect the cable at TT end, short the cable, does the sound go away? If the sound goes away the problem is coming from inside TT. If sound remains, then it is from cable to amp or within amp. BTW, RFI is outside hearing range, 6/8khz high pitch noise may be some sort of feedback loop going on.


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« Last Edit: February 24, 2016, 18:44 by Boxerfan88 »
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Offline malsound

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Re: Help me identify source of interference (RFI?)
« Reply #14 on: February 24, 2016, 18:41 »
what cartridge.
why is it so dam  hard to obsoleted this turning pieces of equipment ?

https://youtu.be/y3RIHnK0_NE

https://youtu.be/FELbmXdS4xM

 

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