Saturday, August 22, 2015

Mu-Metal Part 1

After hearing the amazing differences the BPT power conditioner made in my friend's system (see my review here), I decided to take a good look at the design of my own power conditioner to see if anything could be done to emulate the performance of this fine piece of equipment. I have been using a PowerVar ABC-1200-11 that I already modified installing a 20A toroid common-mode noise-rejection choke on the primary side and some additional secondary filtering. The unit - I thought - was built well and I had already removed the ground loops on both the transformer and the outlets.

But the BPT took power conditioning up another notch and I suspected that the shielding of the chassis and transformer is where the differences hid. So I pulled out some old mu-metal I had lying in a dusty corner, a scissors, and some carpet tape and went to work. I first removed the cover and coated all interior surfaces (3 pieces cut to size and taped in place). Next, I removed the feet and taped a piece on the bottom of the chassis (outside, not inside). I did not reinstall the stiff rubber feet but instead used four pieces of heavy foam to "float" the chassis (this took a stiff pad, one I trimmed from a piece used to keep my knees from getting sore while gardening). These pads were made of different sizes based on the weight they had to hold up (larger=heavier corner). Another piece of carpet tape kept them firmly in place.

Finally, I removed the large toroid transformer from the case and wrapped it first in plastic tape and then covered as much of the transformer in mu-metal as I could (below, above, and a circular strip wrapped all around). I had already replaced the power cord with a shielded #10 3-wire cable so all that was left was to plug it in and turn it on.

OMG! All of the low-level grunge disappeared. It was as if Dyson invented a new vacuum on electronic steroids and it had come to the rescue to clean up AC power. All of the background noise dropped to threshold levels I did not believe possible. The effect was so dramatic that I suspected I was trying to hear things that were not really there. You know how it goes when you get a new car and suddenly that becomes the best and only car you see on the road? It's called a scotoma (a naturally-occurring blind spot) and it means that your eye doesn't see everything you believe it does. Putting it another way, it only sees what it wants to see and ignores all else.

Well the same sort of scotoma occurs in audio to your ears when you get a new piece of gear. It suddenly becomes that magical piece of equipment that bumps the level of your system up a full order of magnitude toward recreating reality BUT in truth it does not. To understand if you are hitting an audio scotoma, you must abandon your ego and any psychological investment you may have to its addition. You just get honest with yourself and become an observer rather than someone with a vested interest. Easily said; not easily done. Here's a side story to help you understand how your emotions can influence your ears (here your eyes).

A friend of mine bought a 4K television and loved the way it looked. He was amazed at the additional clarity and revelation of subtle detail but ignored color (in)accuracy. When I came into the room, I had a totally different experience than what my friend had immediately reaching for the calibration discs instead of watching a golf game on fluorescent green grass. Well, long story short, after tweaking the color closer to the real thing, he decided that he preferred the color the way the manufacturer set it up initially (yikes!). So much for realism.

This true tale can also be relevant for your perceptions about audio. You may initially be thrilled at a change in your system but those tiny filters in your head regarding the money you invested. If you know how much something costs, you immediately attach an expectation to what you SHOULD hear. After all, a $10,000 Audio Research preamp should sound better than a $200 Pioneer preamp, right? Maybe yes; maybe no. But the point is to remove these expectations and evaluate the truth. BTW, the same type of peer-pressure scotoma occurs when a so-called "expert" makes derogatory remarks about your system that are unsubstantiated.

Was I hitting a scotoma when listening to the effects of the mu-metal on my system? I considered this at first trying desperately to NOT hear a change and then to NOT hear an improvement. Alas, this was a truly futile  effort. The changes were both unmistakable and undeniable. I heard more from my system than I ever thought possible. The PowerVAR conditioner only did a partial job at cleaning up the noise coming into my system (sources of this noise were both INTERNAL - of my own doing like refrigerators, motors, etc. - and EXTERNAL - not of my own doing like nearby strip malls, factories, neighbor's workshops, etc.).

Mumetal is a thing of beauty and it is not that expensive. The trick is to cut it with a scissors and not a saw or shears. Wrap it in circles or bend it once (rebending, while possible, is not really a good option). It does leave VERY sharp edges so you also must be careful not to get a steroid-sized paper cuts when handling this stuff. Just be careful and try this yourself. Wrap those power transformers and box up those low-level signal components and be prepared for a shock.

So if my power conditioner responded, what about my preamp? And what about my OPPO BDP-105? See part 2 and part 3 to find out.

Yours for higher fidelity,

Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate by purchasing one of my eBooks or through a PayPal donation, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style (like that of the Discovery Channel), it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.

No comments:

Post a Comment

To comment on this blog, you must first be a member. All comments are moderated.

Note: Only a member of this blog may post a comment.