Sunday, August 23, 2015

Mu-metal Part 3

In Parts 1 and 2 of this 3-part series, I found a new friend: mu-metal. It worked wonders in my line conditioner so I thought I might give it a go in my low-level equipment. In Part 2 I applied the same chassis shielding technique to my OPPO BDP-105 with the same positive results. In this part, we'll look at how (if?) further shielding in the OPPO would benefit and then apply that treatment to my Onkyo P-3000R preamp.

Tearing down the OPPO is getting to be a routine; I've done it now 10 or 11 times for various reasons but I was excited about adding mu-metal to the switching power supply (SPS) section. Reading how nasty this supply is made me believe that there were more issues with SPS than just the high-frequency band smearing associated with their inherent design. And I had a surprise when pulling off the cover of the SPS: mu-metal on the inside. At least two sides of the supply were already shielded so now the side between the supply and the remaining electronics needed to be shielded.

So the first thing I did was to remove the rail and coat it with mu-metal. Instead of carpet tape, I used a spray contact cement on both the cut-to-fit mu-metal pieces and the bracket.



Next, I wrapped a band of mu-metal around both transformers and used a cable tie to hole it in place (yes, I wrapped the already shielded toroid too). WARNING: Make sure that the mu-metal is properly insulated so that it does not short out the wires on the transformer! Remember the edges of this metal is sharp and it will easily cut through any insulation these wires may have.





The next step is to make "hats" for the tops of the transformers and then use another cable tie to hold the hat in place.

While the cover was off, I also added a 0.01uF/200v shunt capacitor to the fuse. Doing this takes care of any thermal non-linearities in the resistance of the fusing element.



Put it back together and all should be well.



First, I want to say that the P-3000R is an under-rated preamp and with a few minor tweaks brings it up to truly high-end quality (change those Full-Wave Bridges to four discrete FRED diodes [2 FWB = 8 FRED diodes] and see for yourself!). So I was happy with the way the preamp sounded with these mods, but hey, what do I have to lose but a little time and maybe a band-aid for the nasty paper cuts on the edges of the mu-metal?

So I first performed the same chassis wrapping as with the OPPO.



And then I did the same transformer wrapping.


Button it up, plug it in, and turn it on. Be prepared to be amazed.

What I noticed was even more low-level grunge removed (I had no idea that it was there). The inner detailing is now a quantum level better than before and I am not exaggerating one bit. The instruments show more nuances than I suspected were captured by the recording process. It is in a word breathtaking.

Now you must realize that your system is a chain and the weakest link limits how much you will observe on yours as compared to mine. Know that all of my gear is seriously tweaked and the attention to detail is unsurpassed. But as you make these changes in your own system, each thing you do you will eventually hear even if the changes are not as obvious. You just have to identify what in the chain is the limiting issue and once it is resolved everything can come alive.

So grab your scissors and glue, buy some mu-metal off eBay, and shield!

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.

http://www.amazon.com/dp/B00QFIAC3G

My other titles include:




Copyright © 2015 by Philip Rastocny. All rights reserved.



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Saturday, August 22, 2015

Mu-metal Part 2

In Part 1 of this 3-part series, I found a new friend: mu-metal. It worked wonders in my line conditioner so I thought I might give it a go in my low-level equipment.

I tried the same cabinet-coating approach I did with the line conditioner in my OPPO BDP-105. I took off the rubber feet, cut out a piece to fit on the bottom, used carpet tape to hold it in place, and then put the feet back on through x-shaped holes I made with an XACTO knife. I also cut a vent hole under the power supply to allow airflow for proper cooling.


I pulled off the cover and coated the three interior surfaces in a similar way (carpet tape & cooling hole).


Note that the holes are much smaller than the originals but the unit does not get any hotter than it did before.

Put it back together and you have a pretty well shielded chassis without a lot of work.

So the surprise is in the sound. This unit has a nicely isolated toroid power transformer so I did not wrap this transformer. But the results were almost as amazing as with the line conditioner in Part 1. The noise floor drops and inner details come alive. If you have ever listened to a preamp with an outboard power supply, this mod has a similar effect. You just won't believe your ears (sort of like hearing a high-quality paper-in-oil capacitor for the first time - you just never forget it).


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 and OPPO BDP-105 responded, what about my preamp? See 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.

http://www.amazon.com/dp/B00QFIAC3G

My other titles include:



Copyright © 2015 by Philip Rastocny. All rights reserved.
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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.

http://www.amazon.com/dp/B00QFIAC3G

My other titles include:



Copyright © 2015 by Philip Rastocny. All rights reserved.
Posted by at No comments:
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