Anyone have any experience with "Mu Metal Magetic Shielding" material (as offered on autotoys website? I'm [still] looking to remove the last bit of empeg native cpu noise from my car system. It is heard during quiet segments. I was thinking of wraping the sled with the material. I believe the non-iron stainless case isn't very effective at blocking emissions. This "Mu Metal" stuff is very expensive (about $40/sq. foot) and I'm still paying off my empeg ;) so any advice is most welcome.

The electronic noise in the system is coming through the signal cables because of ground loop issues.

The magnetic shielding you describe might help RF emissions, but those aren't the source of the noise.

I used the grounding RCA adapters supplied and additionally ran a ground from my amp (in the boot) to the empeg sled. That cut down noise considerably but did not totally eliminate it. I was thinking of using a very thick copper braid (no insulation) betwen the amp and the sled, instead. It would contact many areas of the car as it travels under the carpet, through the center console, to the dash. I would think that would set the empeg and amp at the same potential. The amp has a battery cable welded to the car chassis as a ground. The empeg sled is grounded at numerous points as it is mounted to a metal subframe in the car. I turned up the volume in the empeg to near top and turned down the gain in the amp. I used twisted pair wires with shields. Do you have any additional ideas to eliminate noise?

Regards,
Mark

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that's good and all for the alternator whine (which, btw - I've fixed in my car by running 4 gauge wiring to the amps, hooking up JUST the empeg's side of the rca-ground cables, hooking up a ground loop isolator between the amp and the empeg...)

But the problem that's also there isn't related to the ground loop... find an adapter and hook up regular headphones to the empeg while plugged into the AC power; you'll hear a noise semilar to crunching up aluminum foil... in higher-end systems w/ good speakers this unfortunately gets very amplified...
-mark

...proud to have one of the first Mark I units

I suspect you will be pretty disappointed in the results given the cost of this stuff. Bear in mind it is normally used by CRT manufacturers to reduce the radiated field strength of magnetic emissions, not electromagnetic noise. I doubt the empeg is generating; and in any case, what you are talking about (Faraday cage isolation) can be successfully carried out with metalised netting - I have seen it done, don't laugh - at far lower cost. ANY metal structure can, to varying extents, be used to perform EM shielding. It is all dependent on grounding.

If I were you, I would be looking at the grade of power feed and earth leads used to connect your empeg, not the amp. Pump them to either the same or double used on the unit sled wires; also, you could push this even further on the earting lead since you say your amp is grounding through a battery lead - if the resistance of the earth wire on the empeg is just milliohms above this, and you are drawing a lot of current from the empeg at the inputs to the amp, you could be creating a slight volatage differential at the earth between the amp and the empeg, which will result in current flow, ie. earth loop. Make sure the empeg ground lead runs to where the amp is grounded, regardless of length.

Spend you money on thick power cables, and route from the empeg to the amp, not the other way round - the sled should have 0% influence on the whole thing. Mine is mounted in a wood dash - no grounding there!

I know the sound you describe. I don't hear it on my home system but I did hear it on my car system. However, I finally got rid of it (as well as the digital CPU noise) by running a thick wire between the amp and the empeg sled, while also trimming down the gain controls in the amp. I never tried the Mu stuff.

I got it soooo quiet that I do not hear any noise at all during the quiet passages or on pause for that matter.

I'm finally VERY happy with my unit!


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This really looks as if the preamp gain on the Amplifier was the fix, not the grounding. The only time I've heard the "Mr Scratchy Mouse & Friends" from my unit was outside the sled feeding a very high input-impedance amp. I suspect that the majority of cases where people are reporting this, they have chosen far too high an input gain to their amp.

I would be willing to bet that cutting that earth strap to the sled will make zero difference.

I've actually trimmed my gain down as far as I'm willing to let it go, but still hear the noise..granted I have very sharp Infinity speakers in my setup..
-mark

...proud to have one of the first Mark I units

Have you tried shielded twisted pair cables? I went through two high quality brands before I found really quiet ones.



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