I do not think you will find a tiny galvanized steel box for EDCOR and I can not imagine building it!
Like we talk about a little box and we can not joy with distance + shielding, mumetal is a good idea. Remember, audio band.
But it is expensive and you need very few. Well, if your toroidal? does not have mumetal... and it is inside the same case you can wrap it too.
Like we talk about a little box and we can not joy with distance + shielding, mumetal is a good idea. Remember, audio band.
But it is expensive and you need very few. Well, if your toroidal? does not have mumetal... and it is inside the same case you can wrap it too.
Remember, the main purpose of constructing a case around the Edcor transformer is to shield it from the 50/60 Hz field of the power transformer. As long as your building your M2x in a metal enclosure, concerns with RF shielding are minimal. Another alternative to shielding is to separate the two transformers as far apart as possible.
You want high magnetic permeability metal. 3M 1345 is tin plated copper, copper has permeability that is 100x less than steel, and steel is about 100x less than mu-metal.
Mu-metal - Wikipedia
Composition of Mu-Metal is approximately 77% nickel, 16% iron, 5% copper, and 2% chromium or molybdenum.
Mu-metal - Wikipedia
Composition of Mu-Metal is approximately 77% nickel, 16% iron, 5% copper, and 2% chromium or molybdenum.
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This is from Michael Percy catalog:
"TI SHIELD: Unique composite shielding material from Texas Instruments for blocking EMI & RFI interference. Conventional shielding materials excel either in electrical conductivity or magnetic permeability, but not both. Steel is not conductive enough to be effective at blocking high frequencies, while copper and aluminum are not effective at absorbing low frequency EMI. No single material met both of these requirements until TI developed this copper/alloy 49/copper composite material. TI Shield is effective from below 10Hz up to 10GHz and is currently available only in .014" thickness (28-29ga). Counterpoint utilized sim- ilar technology in construction of their chassis' and found significant audible benefits were to be derived from surrounding audio circuitry with materials that shield against both EMI & RFI. Unlike Mu-Metal, this material may be cut and bent into conven- ient shapes without requiring annealing to restore its shielding properties."
12" x 12"/$32.50, 12" x 24"/$64.50, 12" x 48"/$127.00
Regards,
Yugovitz
"TI SHIELD: Unique composite shielding material from Texas Instruments for blocking EMI & RFI interference. Conventional shielding materials excel either in electrical conductivity or magnetic permeability, but not both. Steel is not conductive enough to be effective at blocking high frequencies, while copper and aluminum are not effective at absorbing low frequency EMI. No single material met both of these requirements until TI developed this copper/alloy 49/copper composite material. TI Shield is effective from below 10Hz up to 10GHz and is currently available only in .014" thickness (28-29ga). Counterpoint utilized sim- ilar technology in construction of their chassis' and found significant audible benefits were to be derived from surrounding audio circuitry with materials that shield against both EMI & RFI. Unlike Mu-Metal, this material may be cut and bent into conven- ient shapes without requiring annealing to restore its shielding properties."
12" x 12"/$32.50, 12" x 24"/$64.50, 12" x 48"/$127.00
Regards,
Yugovitz
Sometimes we need materials that have large losses in reflection and absorption.
* The ferromagnetic material (high permeability) due to its high losses in absorption ..
* A material with high conductivity due to its high reflection losses.
I they are combined on a galvanized base we will have the best of both. With copper directed towards the source of the field to cause a substantial loss by reflection. Material ferromagnetic causes then high absorption losses.
******** ********
Now, here we are trying to reduce the magnetic field strength of the small EDCOR transformers that are on the same PCB as the audio electronics.
In this case, since the emissions are of low frequency, mumetal will suffice. Of course, if we find other cheaper and better material, nothing to object.
******** ********
Other story is a toroidal/EI transformer (without shield) INSIDE the audio electronic case. If we have space, it is cheaper to put galvanized steel barriers, which is what I use with my two amplifiers. Other option, more expensive, mumetal or to buy a good transformer wrapped with it.
******** ********
And then there is the subject of the shielding of the audio electronic box with respect to the atmospheric RFI / EMI. The most effective and cheap is a galvanized steel case coated black and not very perforated (usually in AV case).
With PCBs separated from the steel walls to 1 cm is enough.
If we opt for aluminum, we will need greater thicknesses. If, in addition, said audio is from DAC, phono or preamplifiers, the matter is more important. Unfortunately many of them go in boxes with thin aluminum walls.
Aluminum, especially if it is thin, is more easily perforable but ...
* The ferromagnetic material (high permeability) due to its high losses in absorption ..
* A material with high conductivity due to its high reflection losses.
I they are combined on a galvanized base we will have the best of both. With copper directed towards the source of the field to cause a substantial loss by reflection. Material ferromagnetic causes then high absorption losses.
******** ********
Now, here we are trying to reduce the magnetic field strength of the small EDCOR transformers that are on the same PCB as the audio electronics.
In this case, since the emissions are of low frequency, mumetal will suffice. Of course, if we find other cheaper and better material, nothing to object.
******** ********
Other story is a toroidal/EI transformer (without shield) INSIDE the audio electronic case. If we have space, it is cheaper to put galvanized steel barriers, which is what I use with my two amplifiers. Other option, more expensive, mumetal or to buy a good transformer wrapped with it.
******** ********
And then there is the subject of the shielding of the audio electronic box with respect to the atmospheric RFI / EMI. The most effective and cheap is a galvanized steel case coated black and not very perforated (usually in AV case).
With PCBs separated from the steel walls to 1 cm is enough.
If we opt for aluminum, we will need greater thicknesses. If, in addition, said audio is from DAC, phono or preamplifiers, the matter is more important. Unfortunately many of them go in boxes with thin aluminum walls.
Aluminum, especially if it is thin, is more easily perforable but ...
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Not in this case, however. Here we are talking about one particular source of hum, and how to protect the Edcor from being influenced by that source. We don't need to examine, in this thread, all of the myriad possibilities for noise and all of the remedies.
Hell has frozen over
Tireless DIYer 6L6 removed the Tucson boards from the M2x amplifier he built in April 2018. He has been exclusively using Tuscon IPS boards for nine months(!) This weekend he replaced them with Norwood boards, and is gradually forming opinions about the similarities and differences.
Knock me down with a feather.
Tireless DIYer 6L6 removed the Tucson boards from the M2x amplifier he built in April 2018. He has been exclusively using Tuscon IPS boards for nine months(!) This weekend he replaced them with Norwood boards, and is gradually forming opinions about the similarities and differences.
Knock me down with a feather.
Think I will wrap Edcor with both copper and mu-metal. Then I should be protected from noise in both directions to/from the Edcor. I have also magnetic shielding for the power transformer. Goal must be 100uV max. noise at the output of M2X
The course of this discussion has brought me to the same conclusion regarding the Edcors and the shielding materials will be applied as part of initial assembly.
External shielding of the power trafo is a relatively easy retrofit should that become desirable.
I will take a look at the TI Shield mentioned by Yugo as a possible replacement
for the combination of 3M 1345 and MuMetal.
Thanks to all that have offered information in response to my query, your postings have been very helpful.
Somewhere in Nelson's original M2 thread or perhaps Teabag's M2 group buy thread, someone provided a source for mu-metal boxes that fit the Edcor. I'm trying to find that link myself so I'll post it if I do. Amazon has a surprising variety of shielding materials including boxes but none I saw would fit the Edcor. Percy's latest catalog shows the TI shield as no longer in production. Antek has a line of steel transformer cover for those that need one.
I've been away from my build since Christmas so time to get back to it soon.
I've been away from my build since Christmas so time to get back to it soon.
LOL despite having built all but the Austin, I have used the Tucson exclusively for extended periods because it sounds so good. I have not attempted an indepth comparison = call me lazy or easily pleased..dB
A few days ago I installed the M2x with the Norwoods in my bi-amped OB system, the M2x taking care of the highs and a First Watt F6, the lows. The M2x was terrific almost immediately. Very fast and quiet but the attacks were too strong form my liking. The drums and bass were more prominent than I have ever experienced, tho the drum kit was reproduced very accurately, wood block to cymbals, and the bass was right on, just too prominent to my taste. I put the M2x in place of the F6 (lows) and put back my AlephJ for the highs. This was more to my taste. My Aleph is laid back and very nuanced, The M2x changed the system again. The sound stage opened up, front and back, and the relative relationship between players and sections changed but in an enjoyable way to my ears. I prefer M2x replacing the F6. These were my impressions after a few days of running the M2x constantly. Oh, did I mention the hum? It reminds me of the old mono tube consoles of the 50's. Thanks to all for a fantastic unit. Can't wait to try the other boards.