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In the Forum: Audio Discussions
In the Thread: Building “Zarathustra II” amplifier
Post Subject: The chose of the firewall material.Posted by Romy the Cat on: 4/2/2007

 hagtech wrote:
Yes, steel chassis can be both good and bad.  It likes to conduct magnetic fields, so you have to treat things appropriately.  A little spacing under a choke can go a long way.  Otherise you have a 120Hz motor.  I have another trick that helps with the far field.  The stray magnetic spray from the Hammond chokes is pretty big.  Helps to measure it to see which directions it has maxima and minima.  Then you mount the coil with the proper aim.  Usually away from the input tubes.  My trick is to use two chokes instead of one.  Wire them up in parallel or series, then mount them side-by-side and magnetically out of phase.  You get quite a bit of far field cancellation.  I did this in the Trumpet.

Jim, and perhaps others. I have question.

Packaging how the “Zarathustra II” chassis I have a chose for selection of the materials for my power supply’s firewall (the wall on which the chokes will be sitting). Sure, for the sake of magnetic shielding the steel wall would go fine but I afraid that 2 input chokes with 5A in each will ignite steel very enthusiastically. (I have this problem in my Super Milq). Jim, I what you did in your Trumpet with side-by-side and magnetically out of phase chaos was great and I wonder if I doing it at those currents would be enough. As you see at the image of the Zarathustra PS my chooks are in the oppose wings and one of them care plus and another minus. Still, would it be better to go for some kind of other material wall that would not be vulnerable for “singing” under the stay fields but at the same time do the magnetic shielding. I was thinking perhaps to use an aluminum wall with multiple layers of Magnetic Shielding Coating of to use behind an think aluminum wall a layer of GIRON Shielding Film of NETIC and CO-NETIC Alloys. Did anyone tried it and then actually measured with gaussesmeter the effectiveness of got it?


I am sure that for the folks who do audio design professionally it should be a routine task to make those decisions and in my case, since I do juts one unit I am not restricted by any financial considerations.

The caT

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