Audiophiles journey to solve RFI EMI problems![Objectively]

[sbfx]

Hello! Everyone,


I'm writing this article as I believe there others like me who would have suffered or are suffering from HUM, BUZZ and static noises from other devices in their house coming into their hifi setup's.

Firstly I would like to thank Indian_Ears to help me though every step for resolving the issues and helping me understand better the issues I was facing.

Full full setup is Tubes! [Amp and Pre-Amp] Amps are 845 based and are very susceptible to RFI.

The problem;
1. Cable Box: when even I started my system and the cable was connected on the set-top box I got a HUM from my speakers also when I disconnected it, it was softer but still there.

2. Whenever someone rang the door bell, started the tube light or fan there would be feedback from my speakers!!!


To being with I tried all possible "Audiophile power boxes" Pure Power 2000 which is a AC regeneration box and supposedly gives the best possible power but it couldn't help me eliminate the problem.

I used the Acoustic Revive Ultimate power box but nothing no respite it couldn't contain the faults.

Used Isolation Transformer's and Stabilizers...........

The above devices worked but not to correct faults but change the sonic signature of the setup.

I finally started looking at industrial grade Filters and stumbled upon a 30AMPS Single Phase RFI filter from Elcom, I have a direct line coming in from my Meter-room to my audio setup.

I connected is filter right next to my mains near the system this completely cured my problems of RFI (noise) pickup from the tubes, door bell......

But there still was a HUM so after consultation with Indian_Ears I floated the ground of my setup, i.e. cheated all the grounds except the pre-amp, so in essence the pre-amp is grounding all other gear in the chain.

After everything in place it has played absolutely silently!!! no issues what so ever, there was a small click from the fan which was taken care of by installing a small snubber on the fan switch!!!

This has been a superb learning curve for me and the whole project cost for me less than Rs. 2000/- all expensive gear did play a role in changing the sound but not the problem. This has been the cheapest audio component I have in my setup but the most important non the less

Best Regards,


Satyam Bachani.

 

[malvai]

Thanks for the very useful pointers!

 

[gobble]

Cheating ground is dangerous and there is risk of electrocution.

Do not try this as a first option or an easy solution. A current leak into your chassis will zap the life out of a family member, like a kid.

HTH

 

[santhosh]

Gobble, I think the OP meant cheating ground on all other components except the preamp. The chasis of the other components get grounded through the pre since they are all connected to the pre via RCA.

 

[square_wave]

Good to see here Sbfx. Useful writeup. Thanks.

 

[anm]

didn't the power strips like belkin help in cuttting out rfi/ emi?

 

[gobble]

Gobble, I think the OP meant cheating ground on all other components except the preamp. The chasis of the other components get grounded through the pre since they are all connected to the pre via RCA.

No no no cheating means cheating only!! Not good! Not good!

I will tell to teacher ... hyeah:

Cheers

 

[sbfx]

@ gobble: I understand the hazards of not grounding a component but in my case as long as the pre-amp is connected to the chain everything is safe!!

@ santhol2: thank you for answering gobble's concern.

@square_wave: Anytime buddy!

@anm: I tried PurePower, Accustic Revive, Isolation Transformers..... alas no power strip can take the load of my Amps and if it could also it wouldn't be able to help. I have a dedicated 30AMP line for my audio setup, I doubt any strip can make a difference.

Here below is the link of the RFI Filter;

TYCO ELECTRONICS / CORCOM|20VR6|RFI POWER LINE FILTER, 20A, 700UA | Newark.com


Regards,

Satyam Bachani.

 

[odyssey]

What Gobble is saying is different and he is right - by using a cheater plug you have removed the safety reason for the ground being connected to the chassis. if you do have a short e.g in your amp and you had a chassis ground present, you would have live and ground then saving you rather than the entire chassis being a live conductor. 24 AWG ICs are not going to save you (imagine what would happen if you short 24 AWG wire into your power plug points - they would just melt). If you have kids or other people who operate this equipment besides you, please keep this in mind, if its just you - well better death than suffer a loss in quality hyeah:
I have done the same on occasion but now with kids in the house, I dont go there any more

cheers

 

[anm]

lot of equipment like cdps, dvdps have just 2 pin socket. How to ground their chasis?

 

[odyssey]

you will find that if the unit is inherently supplied with a connected 2 prong plug, the chassis is connected to neutral already (you can check continuity between the RCA neutral and the chassis ground (find a conductive point on the chassis, usually screws). This connection between neutral and chassis is fine if the voltages are low, once they get higher then you want to isolate the two as is typically in the case of amps.

cheers

 

[cmsajith]

From the first post I believe that the OP is trying to solve the Ground looping and he had solved it by Equipment grounding rather the electrical grounding. Electrocution will occur when we try to cheat the electrical grounding.

"i.e. cheated all the grounds except the pre-amp, so in essence the pre-amp is grounding all other gear in the chain.".

Could you please explain how did you actually do that? Is it done by grounding the chasis of all equipments to the preamp chasis using an external wire or through RCA connections? Please explain..

 

[anm]

My Guess - this happens automatically via the ground wire inside rca connectors.
And for cheating, remove ground pin from all other equipments.

So what I understand is that it is fine if you cheat source components' ground, but never do it for power amp. Pls correct me if wrong.

 

[IndianEars]

Hi SBFX,

First of all, Thanks for the mention. However, I must point out that identification & installation of the power line filter was all done independently by you. CONGRATS on your initiative and perseverance that has yielded Excellent end results in your TOP NOTCH system ( I am sure even modest systems with similar problems will benifit by the same solution).

Its good that you have shared this technical solution that once agaiin shows that a little science, properly applied can provide solutions better than simply throwing money at a problem, by buying expensive stuff.

Its also an eye opener that the Rs 1 Lakh and above Power solutions do not incorporate, simple and in-expensive, properly designed line filters !

Congrats to you, again.

 

[IndianEars]

odyssey said:

you will find that if the unit is inherently supplied with a connected 2 prong plug, the chassis is connected to neutral already (you can check continuity between the RCA neutral and the chassis ground (find a conductive point on the chassis, usually screws).

Sridhar, I am sorry, but this is just not true at all.

A 2 pin plug is NEVER directly grounded to a chassis. This would be LETHAL if the user simply inserted the plug the 'wrong' way around into the mains, making the Chassis Completely live, making it lethal to touch.

2 Pin Mains plugs ( such as in a DVD Player ) have their neutral isolated from the Chasis, usually through a High Voltage capacitor...

 

[IndianEars]

anm said:

So what I understand is that it is fine if you cheat source components' ground, but never do it for power amp. Pls correct me if wrong.

I am taking the liberty to respond.

The BEST grounding scheme to avoid Earth Loops ( that result in hum in a audio system) is a Single STAR Ground point.... ie all the Grounds are brought to a SINGLE point, and the External Earth also brought to that single STAR Ground point.

Its called a STAR Ground, because Visually also, all the Ground wires come to this single point and appear as various arms of a Star (actaully an Asterisk * )

When grounding a Music system, the Best Point to introduce the External ground wire is the most sensitive electrical input... usuall the Pre amp. (The Power Amp is the Least sensitive input ). Also, within the Pre Amp it would be the RIAA (phono) input which has a sensitivity of 5 mVolts... atleast 20 times more sentitive than the Line / CD input.

Turntable users will know Very Well what happens if they dont use the RIAA Ground on their pre amp

 

[keith_correa]

The Elcom filters presumably would be available in India too. Right?

Even though our equipment may be free from hum/hiss/hiss/bad noise etc. I, for one, would be better off psychologically thinking that the cause of these noises are blocked.

So, wouldn't this installed in a small enclosure be beneficial to all?

 

[sbfx]

Hi Keith,

Yes Elcom is available locally!, I got mine from Mumbai itself. I'm sure it would be available in different parts of the country.

I see no downside of installing this filter its relatively cheap, has no sonic signature. I was afraid that it would constrain dynamics but no issues what so ever!!!


Regards,

Satyam Bachani.

 

[sbfx]

Here below is a good explanation of Floating Ground;

Floating Ground
Electrical circuits, however, don't necessarily have to be connected to a true earth ground; they may operate with a kind of "floating" ground. In fact, for the designer and engineer, the sense of "ground" may just become an intellectual convenience. For example, a flashlight and other battery-operated devices--even your car--work perfectly well without being connected to a true earth ground. In a car, the negative battery post and the chassis frame serve as the "ground" to complete the electrical circuits in the car, yet the entire car is insulated from the real earth by the rubber tires. In fact, the car is a good example of a self-contained electrical system tied to a common ground--the car chassis and the negative battery terminal. All the electrical devices on the car are tied to that common ground path through the metal car frame and body.

So within one system--say an AV receiver--the ground path may be tied to the chassis and one of the prongs on the AC plug or the third prong an a 3-prong plug, or it may not, in which case it could use an internal "floating" ground that's not connected to the chassis.


Regards,

Satyam Bachani.

 

[odyssey]

odyssey said:


Sridhar, I am sorry, but this is just not true at all.

A 2 pin plug is NEVER directly grounded to a chassis. This would be LETHAL if the user simply inserted the plug the 'wrong' way around into the mains, making the Chassis Completely live, making it lethal to touch.

2 Pin Mains plugs ( such as in a DVD Player ) have their neutral isolated from the Chasis, usually through a High Voltage capacitor...

Hi Indianears
No need to be sorry at all, am here to learn . You are right, I realised this after I saw your post, what I wrote here was an incorrect inference since in some players the secondary output (say using an SMPS) is connected to the common/signal/chassis ground (all three of them) - there I can get a multimeter and check connectivity and I can find it - say between the RCA (signal) ground and the chassis. On some equipment as you mentioned, there is indeed a capacitor and in those, I cant get this continuity. My cheapo DVDP falls in the former category here I do find a short.

On the star ground, as you mentioned the use of the preamp as the primary grounding point is more for reduced hum/noise since the chassis in general can act like an antenna pick up. The preamp is also the central point since all sources are connected to it, so its a logical place to do it. However, I was under the impression that Gobble was referring to the chassis earthing for safety reasons which still doesnt get solved with the preamp grounding in place. As you know some amps provide a ground lift to put more resistance/isolate between the chassis earth ground and the signal ground (common point for secondary voltages/signal points)

cheers
Sridhar