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Old 25th May 2012, 10:11 PM   #4181
pos is offline pos  Europe
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Ok great then, just wanted to be sure everything was normal. I think I will use the screws to make a spacer and let some more air cool the thing as long as it is on a wooden board.
Thank you!
Old 25th May 2012, 10:22 PM   #4182
robbbby is offline robbbby  Canada
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The metal dividing plate on my smps also gets very hot to the touch when idle, seems to be normal.
Old 25th May 2012, 10:31 PM   #4183
Sam Lord is offline Sam Lord  United States
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Hi all,

Thanks for the cable advice!

Russell's example shows the mu of Fermi paramagnetism of aluminum. Those forces are orders of magnitude below those that result from the ferromagnetism of steel, and less than those arising from stainless steel. If the fellow had used a steel plate he would have caused a violent collision, not paramagnetic repulsion. (Yeah, I did have to look it up again, I'm a forgetful old technician and fledgling physics student.) Induced EMF happens with all conductors, but hysteresis is a different animal.

Does hysteresis of a bent steel chassis cause enough EMF in a circuit to measurably affect its performance? Well, of course it depends on the currents, distances, type of steel, and sensitivity of the circuit. As in so many challenges in life, I rely upon the kindness of... better designers. A few years ago I was at an AES convention grilling poor Grant Carpenter (Gordon Instruments, gordonaudio.com) about mic amplification, when he was approached by another, more famous maker of fine pro gear. He and Grant discussed a new converter the fellow was planning, and Grant urged him to replace the steel portion of the other makers' chassis, because the hysteresis was measurable and had ugly (albeit very small) effects on the signal. Aluminum's tradeoff of near-zero EMF shielding for very good RF shielding is best addressed by good layout and grounding. Anyway, I just say to do it because somebody else said so.

Last edited by Sam Lord; 25th May 2012 at 10:54 PM.
Old 25th May 2012, 10:33 PM   #4184
Immelman is offline Immelman  United States
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Originally Posted by StigErik View Post
When it comes to cables, I'm not a believer.....

Me either. $20 oxygen free copper speaker wire and balanced cables with good build quality and low price totally suffice. This is one area not to obsess over or spend too much.
Old 26th May 2012, 03:05 AM   #4185
Sam Lord is offline Sam Lord  United States
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Originally Posted by Sam Lord View Post
"...Russell's example shows the mu of Fermi paramagnetism of aluminum..."
EDIT: Sorry Russell, you were right, it was an eddy current, where a moving B field induces current in the conductor, which creates an opposing B field that creates the repulsive force seen. I sure liked the Fermi paramagnetic angle though...it's real, but less strong than the force created from the induced eddy current. The EMF from those eddy currents still is far less than that from interaction of ferrous casing and nearby conducting paths, but you had the right phenomenon. Now you know why I've taken 35 years to complete a handful of physics courses. I even did the magnet-falling-through-copper-pipe experiment just last summer. Sigh.

Last edited by Sam Lord; 26th May 2012 at 03:10 AM.
Old 26th May 2012, 08:02 AM   #4186
Mark.Clappers is offline Mark.Clappers  Netherlands
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Originally Posted by Juhleren View Post
works as a dynamic break
I remember a Discovery program (maybe about the Trust SSC or another land speed record car) that uses brakes that work on this principle to slow down at extreme speeds. Also the high speed ICE train in europe uses this principle: Eddy current brake - Wikipedia, the free encyclopedia

But I am getting way off topic here
Music is art - Audio is psychoacoustics & engineering
Old 26th May 2012, 02:19 PM   #4187
ufokillerz is offline ufokillerz  United States
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i bought a few of these
Aluminium Chassis for audio DIY (pre amp, headphone amp, DAC, etc.) | eBay a month ago, and finally got them, the height is just perfect, have maybe 2mm of clearance from the top heatsink on the smps600 with the spacers still attached to the bottom of the board. Just enough space inside for everything i need.
Old 26th May 2012, 07:16 PM   #4188
roscoeiii is offline roscoeiii  United States
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Very nice looking case there. What did shipping look like for multiple cases?
Old 26th May 2012, 07:44 PM   #4189
ufokillerz is offline ufokillerz  United States
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Originally Posted by roscoeiii View Post

Very nice looking case there. What did shipping look like for multiple cases?
25 first case 17 each after.
Old 26th May 2012, 09:04 PM   #4190
Sam Lord is offline Sam Lord  United States
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Default anodizing adds resistive barrier

I have a big concern about anodized aluminum enclosures. I used to measure several hundred ohms across some big areas. If masking (where special tapes prevent exposure to anodizing) is done well, you often can't see where it's been used after assembly. And if the anodizing is clear, it's really really hard. I just posted to ask if cOz was masking parts of his ncore cases. For adjoining plates, screws and the huge anodized contact area should eliminate most of the problem. I even worry that Audioquest's XLR connectors (look at their male shells at Cosmic Series) appear to be anodized on surfaces that need to have very low contact resistance. Even Neutrik XLRs look bad on this, I'll need to look for some black-anodized ones that I used to have in large numbers.

AHA! This from Neutrik: "The contact resistance of chromium plated (black chrome) shells is slightly higher than the resistance of nickel-plated shells. That’s usually no problem for all audio transmissions. Regarding EMI at HF transmissions we recommend to use nickel plated cable connectors in combination with chassis connectors with EMI optimized ground contacts." from:
Do black chrome shells have grounding disadvantages? - Neutrik

Geez, I'd never heard of black chrome, had you? Cool!

Of course nearly all non-rare-earth metals begin to surface oxidize even before they solidify in their creation, but the resulting oxide layers still conduct better than anodized surfaces. Good old tin plating is great in this regard, gold better, and I have no clue how well rhodium works. I was also surprised to learn that tarnished silver has almost no increase in resistance compared to the shiny stuff.

Anyway I just wanted to bring this to DIYers' attention.

Last edited by Sam Lord; 26th May 2012 at 09:21 PM.

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