We have bolted together aluminum sheets for decades. The problem is that they don't connect that well electrically. That is why we went to a solid block.
The j-fet follower is just a 2sk240V or a 2sk389V fet pair, biased with two 10 ohm resistors. Works pretty good. V is best, BL will work, GR is useless in this application.
I still would like to know how good silver is in this application.
Most here do not understand that performance may be costly, but 'costly' like Kryptonite does not necessarily mean performance.
For example, for our Mothra series we might use depleted uranium coated with Radium so that it will glow in the dark. It might be best to make a remote control version to keep us away from the inherent radiation.
Plutonium might be too costly and deadly. However, old Soviet nuclear warheads might be interesting to work with.
The j-fet follower is just a 2sk240V or a 2sk389V fet pair, biased with two 10 ohm resistors. Works pretty good. V is best, BL will work, GR is useless in this application.
I still would like to know how good silver is in this application.
Most here do not understand that performance may be costly, but 'costly' like Kryptonite does not necessarily mean performance.
For example, for our Mothra series we might use depleted uranium coated with Radium so that it will glow in the dark. It might be best to make a remote control version to keep us away from the inherent radiation.
Plutonium might be too costly and deadly. However, old Soviet nuclear warheads might be interesting to work with.
Many may find this site of interest
www.emcesd.com/index.htm
Particularly November 2002, Measuring Noise Voltage Across Seams in Enclosures
Regards
James
www.emcesd.com/index.htm
Particularly November 2002, Measuring Noise Voltage Across Seams in Enclosures
Regards
James
john curl said:
All squares are rectangles, but not all rectangles are squares. In Venn terms, it's a question of whether all of one set is included in another, or whether they simply overlap.
Time, time, and again, I see people who mocking high end who cannot grasp one simple idea. They are incensed by the price and--although they phrase it in other terms--the diminishing returns curve as you move up from mid-fi. Their conceptual failure is that they can't, won't, or don't separate the price from the performance.
--1st Listen to it. If you don't hear a difference, go on to the next thing. (It's pathetic how many people will not shut up and listen. In at least some of the cases, their questions and objections would be answered by simply listening.)
--2nd If you do hear a difference, decide whether it's for the better. If not, go on to the next thing. (No, it's not always for the better.)
--3rd (And this is where they go most obviously wrong in their inability to consider price and performance separately.) Decide whether it is worth the price. If not, go on to the next thing.
There's an implied fourth step for those who have the ability to build their own; if it does sound better, try to determine why and see if you can find a way to incorporate the concept into your own designs.
Seems self-evident to me, but an astonishing number of people stray off into dead-ends along the way.
About every third page in this thread, someone has posted something to the effect of, "1000 pages, and I still don't see a schematic for the Blowtorch. Where do I find the schematic?" They miss the rather obvious point that a schematic would do them no good--the parts aren't available. Use the topology and build something yourself.
Grey
Some colleagues of mine once made an enclosure made from two massive alu-parts. (Not an audio related product.) But they got these problems as JC mentions; The do not connect well. They changed the area where the two parts connected to some tongue and groove-like system, giving a kind of "overlap". Originally they had this small joint, but got it covered whit the tongue and grove. Maybe EMC gaskets could be used also. But with aluminium you would not get so good contact. Lots of bolts joining the parts would also help. One bolt in each corner and no kind of overlap is certainly not a good solution EMC-wise.
RK
RK
My idea was 20 mm overlap with the top and bottom, as the side and front should be 40 mm thickness.
But still this is proberbly not ideal.
Anyhow the Blowtorch chassis is made from 3 parts - better than my idea - 6 parts.
Well will be checking the price of a chassis like the Blowtorch - made from 100-120 mm. aluminium sheet.
I would be stupid not to go all the way!
Vogue
But still this is proberbly not ideal.
Anyhow the Blowtorch chassis is made from 3 parts - better than my idea - 6 parts.
Well will be checking the price of a chassis like the Blowtorch - made from 100-120 mm. aluminium sheet.
I would be stupid not to go all the way!
Vogue
I may have posted this earlier in the thread, but then again, maybe not.
A trick commonly used by radio folk in a pinch for an enclosure is to make the casing out of blank, unetched PCB. How to attach the sides? Solder them, of course, which will give you intimate electrical connection between all sides. Yes, the thickness of the copper sheet will be a factor to consider. I'm at work--don't have my reference stuff with me--but from memory, I thick 1 oz. copper is something like .027" thick. (Or maybe that's 2 oz. Within the next five posts someone will correct me if I'm wrong.) I believe PMA posted thickness/frequency for copper earlier, but I can't seem to scroll down far enough to get to it from the Reply screen. I'm sure ordinary PCB, even 2 oz., won't be thick enough for 60Hz, but it does well for RF as per the ARRL guys, and they know a thing or two about radio waves.
An objection that will come quickly to mind is that the box will look like hell. No problem. Encase the PCB box in a nicer looking aluminum or wooden enclosure.
Grey
A trick commonly used by radio folk in a pinch for an enclosure is to make the casing out of blank, unetched PCB. How to attach the sides? Solder them, of course, which will give you intimate electrical connection between all sides. Yes, the thickness of the copper sheet will be a factor to consider. I'm at work--don't have my reference stuff with me--but from memory, I thick 1 oz. copper is something like .027" thick. (Or maybe that's 2 oz. Within the next five posts someone will correct me if I'm wrong.) I believe PMA posted thickness/frequency for copper earlier, but I can't seem to scroll down far enough to get to it from the Reply screen. I'm sure ordinary PCB, even 2 oz., won't be thick enough for 60Hz, but it does well for RF as per the ARRL guys, and they know a thing or two about radio waves.
An objection that will come quickly to mind is that the box will look like hell. No problem. Encase the PCB box in a nicer looking aluminum or wooden enclosure.
Grey
Vogue, you are on the right track. Nobody should have to 'gut' a solid block of aluminum in order to get something acceptable. Still, usually when we make aluminum panels, we also anodize them to get a certain finish. It is not the aluminum that is the problem, it is the anodizing on the machine screws and the surface that makes the problem. I use stainless machine screws (mini bolts) to do the job properly. I also SCRAPE the place where the machine screws mesh, with a special tool, to remove the surface insulation.
john curl said:
John,
I am definitely not attacking the instructor. I'm just sharing personal experience obtained in very challenging conditions. In my sensor application designs (in a semiconductor fab) the best safeguard is layout. Any other approach is just dreaming.
Magnetic fields are picked up meters away and the RF used in the etch chambers is like a bulldoser to most attempts at shielding.
It's been years since college.
Regards, Mike.
MikeBettinger said:I'm just sharing personal experience obtained in very challenging conditions. In my sensor application designs (in a semiconductor fab) the best safeguard is layout. Any other approach is just dreaming.
Magnetic fields are picked up meters away and the RF used in the etch chambers is like a bulldoser to most attempts at shielding.
It's been years since college.
Regards, Mike.
Mike, could you please start a new thread, and shed dome light on this topic?
I think there are quite a few out there whom would listen to your experience with great interest.
Magura
It might help if Mike defined the frequencies that were of interest to him in the professional sense. Blocking RF if you're also interested in RF is one thing. Blocking RF if you're interested in AF is another.
Also, it's useful to define the entry points for troublesome EMF fields. At this point the discussion seems to be centered around the enclosure, which is all to the good, but the power cable (whether AC for an internal power supply, or DC from a remote power supply) and audio cables are another.
Charles Hansen has already weighed in elsewhere against ferrite beads, saying that he believes them to acquire a permanent magnetic field of their own. If I recall correctly, he said the effect can be undone, but that you'll be in a perpetual maintenance mode, given that the beads will remagnetize in time.
One of the things that I try to keep in mind is that I live in a relatively backwards portion of the country. People are either offended or amused when I say that, but it's true. Aside from junk coming in over my AC power lines, I have very little trouble with RF for two reasons: First, there's very little technology in SC and second, my house is in a small valley, so what RF there is flies safely overhead (it's nearly impossible to pick up even local radio or TV stations at my house). As such, I count myself fortunate, but things will deteriorate over time if I stay where I am, and I'm likely to move in the long run and may have to deal with RF in whatever place I end up. So, being a pragmatic sort of fellow, I'd be well served to go ahead and build in a reasonable level of resistance to problems just to make my life easier down the road. I can't say that I'm in a position to have a solid aluminum case made, but less expensive options might be interesting.
Grey
Also, it's useful to define the entry points for troublesome EMF fields. At this point the discussion seems to be centered around the enclosure, which is all to the good, but the power cable (whether AC for an internal power supply, or DC from a remote power supply) and audio cables are another.
Charles Hansen has already weighed in elsewhere against ferrite beads, saying that he believes them to acquire a permanent magnetic field of their own. If I recall correctly, he said the effect can be undone, but that you'll be in a perpetual maintenance mode, given that the beads will remagnetize in time.
One of the things that I try to keep in mind is that I live in a relatively backwards portion of the country. People are either offended or amused when I say that, but it's true. Aside from junk coming in over my AC power lines, I have very little trouble with RF for two reasons: First, there's very little technology in SC and second, my house is in a small valley, so what RF there is flies safely overhead (it's nearly impossible to pick up even local radio or TV stations at my house). As such, I count myself fortunate, but things will deteriorate over time if I stay where I am, and I'm likely to move in the long run and may have to deal with RF in whatever place I end up. So, being a pragmatic sort of fellow, I'd be well served to go ahead and build in a reasonable level of resistance to problems just to make my life easier down the road. I can't say that I'm in a position to have a solid aluminum case made, but less expensive options might be interesting.
Grey
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