Ferrite rings?

[Luis.correia]

Hi guys,

I have a Tv power line at home tompropagate the signal to a second TV I have in another room. Cable is not possible.

This creates a very audible interference with my preamp, a schiit mani.

When I unplug the power line the noise is gone. Everything is grounded... everything was double checked....

Do you thing ferrite rings on the schiit mani power cable could reduce this interference?

Best regards.

 

[Joe Roberts]

If the noise is coming over the AC line through the power supply, you would get a lot more attenuation with a brute force power line filter with a couple LC sections. Surplus units from Schaffner, Corcom, etc are pretty cheap on ebay.

This is basically a case of intentional power line pollution!

Toroids near the unit might help if the signal is being picked up by input leads or the power line from the wall to the unit.

Does the noise occur with no inputs connected? What is the frequency of operation, ethernet frequency/low HF?

 

[whoaru99]

If the problem is a ground loop, ferrites and or power conditioner likely won't help because ground is still (or supposed to be, anyway) carried through.

 

[45rpmspinner]

This is basically a case of intentional power line pollution!

+1

 

[Ken Boyd]

Makes me think of a product that we build as a side line, a Ferrator water purifier.

 

[sKiZo]

Ferret ring?

 

[I LIKE MUSIC]

^^^^It might help take a bite out of the problem.

 

[qdrone]

Ferret ring?

Now that's what I call a " ringing endorsement."

 

[sKiZo]

Maybe try plugging one or the other into another circuit? Might have to string some extension cords to try that, but it'd maybe help point you in the right direction.

Also - polarized plugs? Try reversing one or the other and see if that helps. I'm sure I'd get a severe frowning here if I were to suggest snipping a wide plug down to size so it fits the wall socket backwards ... so forget I mentioned it ... ;-}

 

[whoaru99]

A description of the sound of the noise might be helpful. Hum, buzz, whine, static, etc.?

 

[toxcrusadr]

I find that modern HD TVs and cable boxes create a lot of noise, and it's not all on the power lines. I have a vintage receiver with a rabbit ear antenna on top for FM. Right next to it is my flatscreen TV and DVR cable box. When the TV and cable box are on, I get a lot of hash in the FM and distant stations don't tune in as well. Shut them off and reception improves. Now they're plugged into the same circuit, but I don't get any noise out of the stereo when using other inputs (CD, vinyl), so I have to think it's coming over the air. Same way my iPhone makes noise on my vintage desk radio at the office if I set it too close.

I wouldn't call this intentional, but it certainly seems that there is a lot less care being put into minimizing interference these days. Almost like no one cares about our love of vintage equipment.

 

[sKiZo]

Good point - hence the evolution of the double shielded AV speaker. This one also has a special resin case that soaks up RF before it can hit the drivers - I use it in the "classic" system due to it's proximity to all the other hash emitters.

 

[whoaru99]

Usually "shielded" speakers were intended to minimize distortion of the (CRT) TV picture due to stray magnetic fields. Often they incorporated bucking magnets. With non-CRT TV/display the magnetic deflection is not a factor.

OTOH, maybe the reference is to an active/powered speaker where shielded could refer to several aspects of use...magnetic and electronic/electrical.

 

[Luis.correia]

Thanks for all the answers. It’s not ground issue. I already covered that. The power line is on another socket in the same room. Not in the same socket as the hifi rig.

The sound is like mashing up paper..

As soon as I unplug the power line from the wall.. the sound is gone. Other inputs (cd, etc) are ok. If I use the ART DJ PRE II is also OK. Guess the mani is more open to interference.

I don’t know of the mani picks it up from the power line or the rca cables.

 

[Luis.correia]

Would something like this work?

https://www.onbit.pt/tomada-salicru-6l-sps-safe-master-emi-rfi.html#

 

[Joe Roberts]

Probably not great.. I would look around for something like one of these and wire up your own power strip.

https://www.ebay.com/sch/i.html?LH_..._sacat=0&_oac=1&_nkw=schaffner+filter&_sop=15

Some, like this one,have two filter sections.

https://www.ebay.com/itm/SCHAFFNER-...921464&hash=item4634293b19:g:XgQAAOSweW5U2NEc

Alternatively you can use a large ferrite toroid and wind many turns of the ac cable through it or use a number of snap on cores. #43 material is good at ethernet frequencies, or type #61, but you can use TDK or other "general purpose" beads if that is all you can find.

First you need to know if the signal is coming in on the phono input or not. Disconenct the phono cable and see if the noise stops.

If it does stop when input is unplugged, you should wind your phone cable through those ferrites rather than the AC cable -- or do both.

 

[Luis.correia]

DId some tests today.

The schiit mani using a battery still makes the noise.
The schiit mani using the DJ pre II power supply still makes noise.
If I disconnect the RCA inputs that come from the turntable the noise stops.

Doesn’t that mean that the interference is through the RCA cables?

 

[Joe Roberts]

OK that is quite a tricky situation. I would suggest trying ferrite cores on the RCA cable. If you can find a large enough ring to run many turns through it, that is what you want to do. If you can only find snap on cores, use 6-8. Whenever possible, shoot for multiple turns around the core.

This approach will be more effective if the noise is "common mode"--being picked up by the outer shields of the RCA cables acting as an antenna. Ferrite will help in that case.

If the signal is "differential mode," going down the RCA cables looking like a signal from the cartridge, this can be even more tricky.

I assume that your TT is well grounded to the preamp. Try touching a wire from the preamp ground post to the arm just to verify.

The easy solution, of course, is to turn that stupid AC line device OFF when listening to vinyl!

 

[Luis.correia]

Yes... that’s what i do. But not finding a solution is killing me

 

[Lavane]

Try double shielded cables or a set with the sheild just connected at one end? It sounds like its being picked up by the cables or the TT. Try connecting or disconnecting the TT ground, touch the tone arm, see if it gets quieter, louder, ect. Maybe check the connectors at the cartridge too. Also try a set of rca cables in place of the TT. See if just a set of cables hanging out there not connected to a TT picks up the same noise. That might help find out if its the TT or just the cables.