[intlplby]

RFI and EMI help
A few months ago I moved from Raleigh, NC to São Paulo, Brasil.

I was living at my grandmother's for a few moved and finally found an apartment on Avenida Paulista.

Great location except for one MAJOR problem. Avenida Paulista sits along a ridge, making it one of the highest points in the city. As a result every friggin' radio station tower is within a few hundred meters of me. I have the four broadcast largest towers in the city within 200m. My apartment is sitting right smack in the middle.

I have no problems between my Consonance Cyber-800 power amps and my Consonance Eric-Grand speakers.

And so long as I don't have an RCA connected to the power amps I am okay. However the moment I hook up any of the RCA interconnects I have, I get some major RFI and EMI.

Here's what I have as far as cables to work with

a) Cheapo Monster RCA interconnects

b) Cheapo generic RCA interconnects

c) Decent directional Consonance Billie interconnects. The have directionality but I don't know if this means that the copper braided shielding is connected to one of the RCAs or if it is the "snake oil" directionality.
(http://www.ornec.com/Opera_Consonanc...les_QQC100543B)

d) homemade 4-wire Litz braid silver interconnects with each of the four wires PTFE insulated and then a braided metal sheath that is soldered to one of the RCAs but not the other (directional).

Is there a way I can modify the homemade cable to solve this boondoggle? Can I unsolder the sheath and add a drain wire? If so, where do I connect the drain wire to?

Is there any solution using "fast" capacitors on the shielding or anything else?

I need the most hardcore RFI & EMI solution you can imagine.

 

[intlplby]

okay... I think I got a handle on the RFI..... the interconnect shielding is grounded at the source end (pre-amp) and on the power amp end I soldered a wire to the shielding and ran it out and connected it to the chassis of the power amp... this appears to have killed most of the RFI....

however, doing so has created a ground loop and therefore a buzzing sound.

Where should I ground the lead I made to kill the ground loop?

Ideally I should have a .01uf or .47uf ceramic disc capacitor in line with the lead, but alas, I have none on hand.

will the disc cap kill the buzz? other solutions?

 

[Pars]

The capacitor might help the problem, although I don't understand why you would get a ground loop from connecting the shield at both ends, since yo presumably already have a ground connection within the cable itself for the negative lead. I think I had read somewhere (Counterpoint, AltaVistaAudio or Mike Elliot) regarding a standard practice of having a 0.01uf ceramic going from the center pin to shield on all RCA jacks.

Shielded interconnects are probably a must in your situation; preferably coaxial.

 

[nikongod]

first: if chassis ground is not the same as signal ground in the other amp, there can be a TERRIBLE ground loop. im not so sure i like the idea of adding capacitance on the RCA jacks. shield is also ground, and driving the extra capacitance may totally screw up the HF response of some devices.

for the whole thing of running the shield elsewhere than the RCA, it should go to earth ground. if the amp has a ground lug, there you go.

second: have you tried turning the interconnect with the shield tied to ground around? the wire may be directional, but you seem to have larger problems.

third: are you running the shortest interconnects you can possibly run? it may require careful rearranging, but it is worth it even in systems that dont have issues.

finally, have you considered building a feraday shield for the whole mess?

edited:
have you tried installing ferrite beads/rfi supressors on your power cables? also a worthy experiment.

 

[threepointone]

the most serious, hardcore solution would be to modify all of your equipment to work with balanced interconnects. The most serious way is to totally redo the whole amp (might as well make a new one at this point). The slightly more feasible way would be to just redo the back panel with xlr connectors (or maybe keep the RCAs) and piggyback a couple unbalanced-balanced converters onto the circuit.

but you'll probably want to look for some simpler basic shielding problem first before going either way =)

 

[pinkfloyd4ever]

I know of these http://www.partsconnexion.com/catalog/accessories.html (click the "ERS" tab @ the bottom) and http://www.partsconnexion.com/catalog/wire.html (click "Tin Copper Braid") I'd put ERS paper in your amps and the braid around the interconnects. And no, I don't work for parts connexion.

 

[intlplby]

the interconnects could be shorter, but i'm reluctant to cut the interconnects i made because they are silver interconnects i made and I don't want to waste half a silver cable by chopping it up.

i'll just make a new cables.

a few questions? can I double up braided metal shielding to maximize the shielding? i.e. get some canare star quad and float the cable shield by connecting it only at the source end and then put metal braiding that floats completely with a drain wire to the ground post on my Belkin PF40 power conditioner?

if I have a fully floating drained to ground shield, does a ferrite core still have the possibility of affecting the sound of the cable?

caging and grounding the entire system is the last choice. the system is too pretty do do something like that.

i haven't tried ferrite beads yet. i'll do that tomorrow if i have time to leave for lunch to get them and can find them.

i'd like to try the balanced idea, but think my pre amp and power amps can't be made to have balanced outputs without a ton of work

Cyber800
Cyber800

 

[Pars]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif I don't understand why you would get a ground loop from connecting the shield at both ends, since yo presumably already have a ground connection within the cable itself for the negative lead.

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif first: if chassis ground is not the same as signal ground in the other amp, there can be a TERRIBLE ground loop.

Sorry, I misread your initial post as connecting both ends to signal ground, instead of one end to signal ground, one end to chassis...

 

[Sovkiller]

Try some better RFI and EMI rejecting conductors, Blue Jeans Cables has one particular Belden model that was designed for extreme cases like yours, and it will cost far less than the monster ones...be careful with grounding, case ground, and audio ground, not always are the same, and you can create a ground loop, even though I think that it will be good to ground all cases as well...

 

[kc2ixe]

Do a web searh on RFI "Pin 1 problem"

Also, most of the noise your getting will be "common mode" - get some type 43 or 37 Ferrite rings - say 2.5" diameter (Hello Digikey) - wrap your interconnect around the ferrite doughnut a few times - as close to the connector as possible, and re-connect

Make friends with a local ham - they KNOW how to deal with RFI. frankly, most consumer goods don't really meet part 15, so hams learn to both fix their own stuff, and advise neighbors how to fix their stuff

 

[intlplby]

i got a 2.5" ferrite ring... i don't know what type it was... i used the wiring diagram on this page:
Radio Society of Great Britain

I put six windings on each side.

it didn't help much.

I even tried making a cable using a firewire cable since I figured it's the most shielded thing I got.

this is driving me absolutely nuts.