Idea to reduce RFI

Milen,it is very simple.Just connect one end of the drain wire and the capacitor to the anode.Then the other drain wire from the fellow interconnect and another capacitor is connected to the cathode of a 9V DC battery.I use a pair of Audio note copper paper in oil 0.22uf capacitor (best sounding so far) ,so one end of the capacitor is connected and the other end is left unconnected.Also I discovered that ferrit core around ONE proximal and BOTH the distal terminal of the speaker cable definitely help to improve the sound as well.Happy tweaking!

Milen,it is very simple.Just connect one end of the drain wire and the capacitor to the anode.Then the other drain wire from the fellow interconnect and another capacitor is connected to the cathode of a 9V DC battery.I use a spare pair of Audio note copper paper in oil 0.22uf capacitor (best sounding so far) ,so one end of the capacitor is connected and the other end is left unconnected.Also I discovered that ferrit core around ONE proximal and BOTH the distal terminal of the speaker cable definitely help to improve the sound as well.Happy tweaking!

Tigerclose, mind share how the active shield is conducted? how you actually connect the 0.22uF cap? any schematic or wiring diagram? thx in adv

Well, it seems I am the resident expert in this respect, so I thought I might help a little. You cannot shield anything with ERS cloth since it does not work (does nothing) under real testing. Do not waste your money. The best thing to do is yank your siding and cover the side of your house (or more) with MuMetal or any type of ferrite metal roll. For a smaller scale project, you may attach to walls around the equipment. It is wise to use two or more layers of dialectic with non-conductive spacers, this attenuates induction within permittivity of the two combating e fields when inducted from the air in reversing current. The non-conductive spacers may be selected of differing thicknesses to address the actual frequencies causing issues.

Sadly, this is part of buying a home near radio towers, cellular / microwave towers, repeaters and power stations as the source induction can occur with a miriad problems in the audible frequency once your equipment makes sense of it. You can go "Mork and Mindy" and wrap everything in shields till you find the worst inducting unit or cable. Some power conditioners will help if the signal is coming in from house wiring or the power path... but this could be into your signal path and a conditioner or other "plug into" isolator will do nothing. Induction occurs into wires, IC's, PCB's and other small ferrite objects, even if we don't like it.

Hope this helps!

I was also troubled by an unshielded interconnect previously.So I added an copper braided shield which was gounded with a drain wire.The drain wire is then connected to a small DC battery and a 0.22uf capacitor.WOW!!the sound was fantastic very life-like,much more detail and 3 D like.The soundstage just open up with greater depth and height.I think this active shield help eliminate the RFI/EMI. Now I can never enjoy without the DIY active shield on,it is that good.

Get a power conditioner.

i change some IC and it solve the radio frequency pickup. thx guys.

Any idea on reducing the noise floor further? i read bout dedicated lines but not practical for the at the moment.

My experience with using amps on isolation transformers is that they do suck a bit of life out of the music. Lack of attack and smoothed over sound. I've tried probably a dozen power conditioners with amps, none have worked thus far.

I did use Bybees in my former amps, at that time I didn't detect any downsides, couldn't really tell you if they affected RFI as that problem had already been resolved. I do have some Bybees ready to install in my present amp, just haven't gotten around to it.

Milen,

Try it and let us know. I don't have any experience w/them. Cheers,

Spencer

Spencer, if power conditioners suck the life out of most amps, how bout isolation transformer?

Kirkus, thanks for the thorough explanation, thats really helps. I did change to better IC, it did eliminate the radio frequency, but hum still present. maybe its caused by my tube preamp.

anyone try bybee? does it helps?

>> For more information on the subject, I recommend Bill
>> Whitlock's excellent papers (available at
>> jensentransformers.com), which I agree with the vast
>> majority of. I also highly respect the work of Douglas
>> Self and recommend reading all of his stuff . . . even
>> though on this particular subject I differ with his
>> conclusions.
Kirkus, thanx for the reading recommendations. I'll check them out.

>> That is, start with just power amp and speakers.
Now, how does Milen007 get music to play thru the speakers? Run the CDP directly into the power amp?

Uh, er, you don't LEAVE the system this way for listening to music. You stick your ear by the speaker to see if, in the original poster's case, the offending "radio channel" can be heard. If it can, then the interference MUST be solved in this configuration BEFORE it can be reliably solved in a more complex one.

the FM signals are somewhat AM. So, the possibility of catching a FM station thru Milen007's system is quite real.

Nope. FM interefence on baseband audio electronics is manifested mainly has hum and buzz, that changes in intensity and timbre as cables are moved around.

>> very few balanced input stages have much common-mode
>> rejection above 3KHz or so.
Another terribly ignorant statement!!

Whatever, dude. Actually, 3KHz is even quite optimistic, especially for active balanced inputs -- most I've measured deteriorate up from 60Hz by at least a single-order slope.

For more information on the subject, I recommend Bill Whitlock's excellent papers (available at jensentransformers.com), which I agree with the vast majority of. I also highly respect the work of Douglas Self and recommend reading all of his stuff . . . even though on this particular subject I differ with his conclusions.

You can't hear RFI. The RF signal must be demodulated. Corrosion at a connection can create a diode which provides the demodulation. So, clean all your connections.

I have never experienced the RFI problem except long ago with a turntable/phono (high gain) connection. I have experimented with trying to induce the problem using cordless phones and cell phones activated just inches away from the audio equipment, but I hear no effect.

One cheap, easy way to see if interconnects are your problem is to temporarily try the typical cheap ones that come w/VCRs, you know the type(i.e red/blue/yellow, 3 all together). Sonically they suck, but they are very well grounded! If RFI disappears with them, you'll know to upgrade to good grounded interconnects.

Search the archives for advice on grounding your system as a whole. Best solution is one ground from the rig to a copper rod buried outside. You can read for hours on best way to do this.

Power conditioners suck the life out of most amps. Avoid if possible.

The suggestion to rearrange gear 90 degrees, didn't mean to move it to a different wall. Just turn each component 90 degrees on its shelf and see if it makes a difference.

Another crazy thing to try is take aluminum foil and wrap it around where interconnects attach, particularly on preamp. Jud Barber of Joule Electra suggested this to me a long time ago when diagnosing an RFI issue. If it helps, try adding Cardas caps on your unused inputs and outputs. Cheers,

Spencer

>> 06-21-08: Kirkus
>> If you want to eliminate an RF interference problem,
>> then you must take the system completely, totally
>> apart, then add each component to the system one at a
>> time to see the point at which the RFI appears.
good advice, in general.

>> That is, start with just power amp and speakers.
Now, how does Milen007 get music to play thru the speakers? Run the CDP directly into the power amp? If yes, the 2V CDP will most likely saturate the power amp input stage & cause high SPL (distorted) sound. He could buy some in-line attenuators but then that's costing Milen007, which he might not be willing to do (?)

>> Second, if you can hear the audio signal (modulation),
>> it's an AM transmitter, not TV, or FM,
Theoretically you are correct - FM is constant envelope modulation. However, in really life due to interference from buildings, foliage, terrain, etc the FM signals are somewhat AM. So, the possibility of catching a FM station thru Milen007's system is quite real.

>> And third, the 'balanced' nature of balanced
>> interconnects have no effect on RFI
this statement could NOT be further from the truth!! It seems to be a statement you have made out of total ignorance in the matter.
Go look at any RF layout whether it is I.C. layout or PC board layout & you will see differential circuits used exclusively! Differential circuits ARE balanced circuits. It is one very important way to curb RFI.

>> very few balanced input stages have much common-mode
>> rejection above 3KHz or so.
Another terribly ignorant statement!! If your statement is true then the designer of that circuit has failed miserably!
If the designer has designed the circuit correctly the CMR frequency range would be atleast upto the -3dB corner & even upto the unity gain frequency of the circuit.

If you want to eliminate an RF interference problem, then you must take the system completely, totally apart, then add each component to the system one at a time to see the point at which the RFI appears. That is, start with just power amp and speakers. Add the preamp. Add each source, one at a time. And so on. Always fight the problem with the simplest possible system that exhibits it.

Other things about RF . . . first, it doesn't care which is an input and which is an output. Any wire of any kind that goes into or or out of your components' metal boxes can bring RF with it. Second, if you can hear the audio signal (modulation), it's an AM transmitter, not TV, or FM, or communications equipment (exceptions being some amateur radio, CB, and airplane-to-tower). And third, the 'balanced' nature of balanced interconnects have no effect on RFI -- very few balanced input stages have much common-mode rejection above 3KHz or so.

Also, unshielded interconnects are really asking for RF problems . . . that's why they pretty much don't exist outside the world of small-market specialty audio. Ferrite (torroid) coils on cables right next to the connectors can help . . . but they usually work best at frequencies quite a bit higher than the AM broadcast band. In your case, I'd start by shielded interconnects, making sure that your electrical outlets are properly wired and grounded, and making sure that none of your equipment has loose RCA connectors.

well, at one point my brother had the same issue - FM radio channel playing thru his speakers! He solved it by using XLR interconnects. The balanced interconnects have the FM channel on both + & - wires but of opposite polarity thereby effectively cancelling the FM signal. He now does not have that issue any more.

Shielded cable is good but remember that it adds extra capacitance which reduces the cable's bandwidth + adds a cap load to the amp. Sonics could/will change. In some cases (maybe yours) you might have no choice.
Power conditioner: I've found that the best solution is to not use one! They always change the sonics for the worse (the ones I tried). However, YMMV.

I had a similar problem with my turntable and switched phono cables and the RFI disappeared just like that. So it may be as simple as changing an interconnect or two in your system.

BTW, I tried ferrite clamps on various cables and it never did anything.

Several years ago I had an excessive RFI situation (radio station coming through stereo), in my case it was speaker cables with little or no shielding. Replacing with well shielded speaker cables solved the problem (Kimber Trifocal XL). Also, make sure all interconnects and power cords are well shielded.
As Elizabeth mentioned, moving cables around can have great effect. I suffered the radio station problems only when my system was set up on the long wall, in short wall setup I had no problems.
A power conditioner may or may not help, I was using a PS Audio P300 when I had my radio station probems.
ERS paper and Shakti Stones over transformers may help as well. Too much ERS paper will damp and veil the sound so use judiciously.

I want to elaborate on Elizabeth's point about wires acting as an antenna. An AC system is a giant antenna that collects noise from the neighborhood and delivers it to your components through their power cords.

I live in an apartment with two restaurants a floor below me, refrigeration units a floor above, and a cell phone tower on the roof. You couldn't ask for a worse situation in this hobby. I wrestled with RFI for a long time before I stumbled into a forum where someone suggested a power conditioner. Being cheap, I bought a used Monster Power Center HTS 1000. It was worthless in my opinion. When I switched to a Quintet, the noise completely disappeared. I have absolutely no noise coming out of my speakers with the system powered up and the volume at 3/4.

Not to change the subject, but you'll have to experiment to figure out whether or not to plug your amps into a conditioner. Initially, I did just that because I only had two receptacles on the wall. I took the advice of someone on Agon and installed a second outlet which gave me the chance to hear it both ways. That's when I noticed a weird compression when the amps were plugged into the conditioner. The background was dead quiet, but the music had an artificial veiled quality. YMMV.

I've been using a PS Audio Quintet. You'll see them used for around $400. The Duet has the same design, but only four receptacles. It's around $200 used.

Thanks for all the replies

Elizabeth, how to reroute the particular offending wire? how to locate one? by changing to diff cable?

Musicslug, no its not visible. havent tried rotating. but my room does not permit it. has doors on left and right.

Mingles, no i havent. which brand do you suggest? budget maybe $1000 or less. will $2000 one makes substantial diff from $1000?

thx

I had a similar problem. Connecting my sources and preamp to a power conditioner eliminated all RFI. If you're not using one, I highly recommend it.

if the tower is visible from inside your home, is in a straight line from your stereo through the window, you might be able to improve things by changing the location of the equipment

also, some equipment will be be better shielded if you rotate it 90 degrees