Author Topic: Help me identify source of interference (RFI?)  (Read 17219 times)

Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #15 on: February 24, 2016, 19:03 »
Bukit panjang too
Bangkit area
Same problem
Tried everything for 2 yrs
It neva goes away
Gave up.

so you're saying you heard the exact noises I heard? wow something is up with this area if that's indeed the case.. I'm at Fajar..

If you disconnect the cable at TT end, short the cable, does the sound go away?
do you mean to short the tonearm wires together? I removed the cartridge and the sound is still there, but I didn't try shorting any wires or connectors together yet. I'm using the AT-95e (green) cartridge that comes with the LP-120.

I'm aware that RFI isn't audible, but it could cause interference or be demodulated somehow.. reasons of which are beyond me..

I did plug in a RCA->3.5mm cable into the phono and plugged it to my phone without playing anything in case it blew the phono on my amp.. and the sound went away.. so I'm sure the turntable is causing/picking up this noise somehow.. if francishuang says he got the same problem in Bukit Panjang area then maybe something is transmitting and only turntables can pick it up? turntable cartridges output is on the order of milivolts and is amplified hundreds of times to be at line level, maybe that explains why my other inputs do not pick up these noises? I can be wrong.. just an informed guess at this point..  :-\
« Last Edit: February 24, 2016, 19:10 by ptjw »

Offline jerome_the_lang

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Re: Help me identify source of interference (RFI?)
« Reply #16 on: February 24, 2016, 19:29 »
When you plug a pair of RCA cable into the phono input of your amp, while at the other end of the RCA cable nothing is connected (just leave it lying down on the floor, and no shorting) - do you hear any "eeeee" noise?

No, right?

But as soon as you plug the unconnected end of the RCA cable into the turntable's output, then "eeeee" sound comes back.
(You may turn volume knob to zero while doing this, and slowly turn it up again)
(Also, for the sake of this test, remove the headshell)

Correct?


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Offline jerome_the_lang

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Re: Help me identify source of interference (RFI?)
« Reply #17 on: February 24, 2016, 19:39 »
Can you want to open up and take pictures of turntable's output terminal box where the tonearm wires are soldered to the RCA output jacks?

Does the TT use universally colour coded schemes for their tonearm wiring?

Red - right channel conductor
Green - right channel ground
White - left channel conductor
Blue - left channel ground
Black - earth

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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #18 on: February 24, 2016, 20:11 »
When you plug a pair of RCA cable into the phono input of your amp, while at the other end of the RCA cable nothing is connected (just leave it lying down on the floor, and no shorting) - do you hear any "eeeee" noise?

No, right?
nope, tried this and there is no "eeeeee" noise

But as soon as you plug the unconnected end of the RCA cable into the turntable's output, then "eeeee" sound comes back.
(You may turn volume knob to zero while doing this, and slowly turn it up again)
(Also, for the sake of this test, remove the headshell)

Correct?
yes, correct, and the noise increases when i increase the volume on the amp, and vice versa when decreasing the volume, which is how i concluded the sound must be picked up or caused by the turntable and not the amplifier.

Can you want to open up and take pictures of turntable's output terminal box where the tonearm wires are soldered to the RCA output jacks?

Does the TT use universally colour coded schemes for their tonearm wiring?

Red - right channel conductor
Green - right channel ground
White - left channel conductor
Blue - left channel ground
Black - earth
unfortunately i do not have time to open up the turntable now, but the tonearm wires follow the color coding that you mentioned.. also even if i did open it up they are wrapped in foil now and would be hard to see  :P
« Last Edit: February 24, 2016, 22:06 by ptjw »

Offline Jag

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Re: Help me identify source of interference (RFI?)
« Reply #19 on: February 24, 2016, 20:13 »
Is the TT grounded to the amp?
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Offline malsound

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Re: Help me identify source of interference (RFI?)
« Reply #20 on: February 24, 2016, 20:34 »
Quote
Can you want to open up and take pictures of turntable's output terminal box where the tonearm wires are soldered to the RCA output jacks?
<a href="http://www.youtube.com/v/T8sUuaclrZ4&fs=1" target="_blank" class="new_win">http://www.youtube.com/v/T8sUuaclrZ4&fs=1</a>
why is it so dam  hard to obsoleted this turning pieces of equipment ?

https://youtu.be/y3RIHnK0_NE

https://youtu.be/FELbmXdS4xM

Offline cody

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Re: Help me identify source of interference (RFI?)
« Reply #21 on: February 24, 2016, 20:37 »
i do have the same problem when playing tunrtalbe , me at Yishun.
what i noticed that it happen after upgraded a new life outside my block , nothing change to my hifi system.
during the troubleshooting what i find out i cant use MM cartridge it can pickup the interference but MC cartridge all OK(with the same system)
so i suspect it came from the new upgraded life EMI.

Offline jerome_the_lang

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Re: Help me identify source of interference (RFI?)
« Reply #22 on: February 24, 2016, 21:01 »
So did this turntable eeee sound started after you did the modifications?

 ;D




Now try change to another mm cartridge....

Or alternatively, try borrowing an mc cartridge to check if the noise disappear.
Many times I tried in the past - put on mc cartridge - the eeee sound disappear.
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Offline ptjw

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Re: Help me identify source of interference (RFI?)
« Reply #23 on: February 24, 2016, 22:12 »
Is the TT grounded to the amp?
Yes turntable is grounded to the amplifier grounding post, and I added a wire to the earth connection on the mains socket to the grounding post as the Onkyo is originally a 2 pin plug and doesn't have an earth connection. with this additional ground wire the noise floor is audibly lower and my other inputs are very quiet.. even the whining noise is quieter, tried it by removing the ground and connecting back with my ear to the speaker.

the turntable already had this whine before the modification, I did the modification thinking that the preamp might be the cause of the whine, but removing the preamp made the audio clearer, AND made the whine CLEARER as well....  ;D

unfortunately the phono on the Onkyo is for MM carts only, and so is the spare external preamp I have (TCC-750, also MM only).. hmmmmm but it seems I'm not the only one, maybe HDBs have lots of things going on that turntables can pick up?  ???

Offline tzesian

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Re: Help me identify source of interference (RFI?)
« Reply #24 on: February 25, 2016, 13:02 »
Just seen this thread.

I'd extensive experience in this area... Not easy job, it's due to bad grounding (mainly using big copper area on the PCB as ground) + absence of a anti- RFI interference network.

The cuurent amp I'm building, with seperate stage grounding plus anti- RFI interference filter will solve this problem, be it tube or solid state. Do sms or whatsapp me, I might be late in reply as I'm travelling quite frequently.

Sincerely,

TS Lim
(98528400)
Music without "life" is a biggest mistake !

Offline tzesian

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Re: Help me identify source of interference (RFI?)
« Reply #25 on: February 25, 2016, 13:05 »
And of course, phono amp build by me is guranteed to be free from any of these symptoms
Music without "life" is a biggest mistake !

Offline wizardofoz

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Re: Help me identify source of interference (RFI?)
« Reply #26 on: February 25, 2016, 14:26 »
You should meter out the grounds on the TT and especially the tone arm and cart areas as it could be a bad ground connection also.


I have external preamps too and don't seem to suffer so much anymore since changing things around with different leads etc...but occasionally I get it thru all sources very faintly...oddly my wife hears it but not me...I thing she gave up complaining...or its gone maybe
I have a pile of stuff that pushes out squiggly waveforms from smaller squiggly waveforms that sometimes come from 1's and 0's.
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Offline cody

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Offline ssi2

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Re: Help me identify source of interference (RFI?)
« Reply #28 on: February 25, 2016, 22:15 »
I have exactly the same issue and am staying in Jurong West area. It can be quite irritating and it robs off the pleasure of listening.
I have 3 TTs connected to the system but only one TT has this problem. After some trouble shootings lasting few weeks, another TT was affected. So I unplugged all the cables (inter connect and power cables) and connect them so that the ICs do not criss cross with the PCs. After so much time and effort, one of the phono amp (sonic frontier) stopped working. So now I give up for the time being and only listen to my DIY TT. 





Offline Retrotube

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Re: Help me identify source of interference (RFI?)
« Reply #29 on: February 25, 2016, 22:21 »
Hi Ptjw. You have gone so far, so one more check won't be a stretch. This link below has very interesting expert discussion about noise from neon indicator lamps.

In the 80's I messed up my Thorens TD165 introducing "eeeee" noise when I added a neon indicator bulb to show power on. Had to remove it immediately, just laugh at what silly thing I did.

Just a wild guess.. may be a good next step to look nearby neons and inside your TT to examine any neon bulbs, aged led drivers, aged led indicators, re-wet possible dry solder joints, the likes. Wish you well.

http://www.eevblog.com/forum/projects/neon-bulb-noise/
« Last Edit: February 25, 2016, 23:18 by Retrotube »

 

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