Deang Posted December 23, 2005 Share Posted December 23, 2005 Well, it is a form of cross-dressing in a way. I built up the Super AA's with Bob's GE cans, and my other networks are basically Type AA's built with AudioCap PPT Thetas. I finally have all the parts I need for my suped up Super AA's, and I'm looking forward to getting those built up to close out the trio. Quote Link to comment Share on other sites More sharing options...
sunburnwilly Posted December 23, 2005 Share Posted December 23, 2005 Hey , Those are My Old Caps !!! I was wondering what you did with them . A little steel wool and shilac fixed them right up ! " So what do you have planned for my Zeeners ? " [8-|] Quote Link to comment Share on other sites More sharing options...
sunburnwilly Posted December 23, 2005 Share Posted December 23, 2005 Heres one of your Old Super AA's in it's new nest . [][] Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted December 23, 2005 Share Posted December 23, 2005 Dean, That litz inductors is cramed right against the capacitor can! That's not good! AL K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted December 23, 2005 Share Posted December 23, 2005 Dean, I did a little study using a .2 mHy Solen Litz inductor. I measure inductance and Q setting on a wood table, and on a metal can bathtub cap. As you see the inductance went down from .201 mHy to .149 Mhy and the Q factor went down by a factor of over 5 times! You would get better Q with a solid wire inductor sitting in the clear! P.S. Spacing the inductor away from the cap by 1 inch yields .198 mHy with Q=41.4. AL K. Quote Link to comment Share on other sites More sharing options...
ajsons Posted December 23, 2005 Share Posted December 23, 2005 Dean, Is there a schematic of your crossovers somewhere on this forum? I am interested. . Quote Link to comment Share on other sites More sharing options...
Deang Posted December 23, 2005 Share Posted December 23, 2005 Too funny Willy! Al -- I checked that too before I mounted it. I couldn't check for 'Q', but I did have it hooked to my inductance meter and moved it up and down along the can to see if the meter moved any -- it didn't. I just took the meter upstairs to double check and hooking to tap 5 and the lead into the 40uF cap I got a reading of .194mH. Ha! Those folks at GE thought of everything. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Dean, I think the old cap that Al used in his test was a steel can. The aluminum cans have much less effect on air core inductors. Rule of thumb would be to be to keep anything that is attracted to a magnet well away from air core inductors. Bob Quote Link to comment Share on other sites More sharing options...
mark1101 Posted December 23, 2005 Share Posted December 23, 2005 Dean, I would love to try the Super AA with the GE cans just for a comparison. If you shipped me just 1 I'd only keep it a day or two and return it. Hint.[] Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted December 23, 2005 Share Posted December 23, 2005 Dean, Bob, Yes, that cap does have a very heavy can. I wouldn't doubt it's steel. You can consider it a worst case situation. Any conductor near a coil will act like a shorted turn though. It should be avoided if you can. Aluminum and brass are fairly good conductors and would not generate the losses that steel will. It also looks like the coil is leaning against a curved surface. IF that's the case it's onl;y touching over a small area. That is less destructive than against a flat plane like the test I did. AL K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted December 23, 2005 Share Posted December 23, 2005 Bob, Dean, UPDATE: That cap is NOT steel. A magnet does not stick to it! I just tried it again by sitting it on a cap that definitly IS steel. The inductance goes up when I lay the coil on that cap. It goes up to .204 mHy but the Q goes down to 7.5. If I space the coil above the metal surface by about 1 inch the Q goes up to 32.5 and the inductance goes to .200. Aluminum has no permiabiltiy so the only effect it would have on inductance would be eddy current "shorted turn" and DCR losses. Inductance an Q would go down. With steel, it has positive permiabiltiy AND shorted turn effects plus it's a band conductor. Those two effects on inductance seem to cancell each other out but the eddy current losses kill the Q but good! The bottom like is to keep ANY metal away from the inductors if you possibly can. If you are limited for the room to mount it elseware, just space it up over the metal surface with a wood block about 1 inch thick. That could even be a convenient way to mount it. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Al, Depends on what the metal is. Conductivity is not the real answer. Brass and stainless steel have almost no effect on an air core inductor. Steel has a major effect. Picture below is a 500 uH air core inductor with nothing in the core except air. Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Same coil with 4 stainless steel screws. Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Same coil with one paper clip inside. Bob Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 23, 2005 Share Posted December 23, 2005 Well the paper clip scores higher so it must be better[] Quote Link to comment Share on other sites More sharing options...
Deang Posted December 23, 2005 Share Posted December 23, 2005 I'll move the coil. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted December 23, 2005 Share Posted December 23, 2005 Bob, That's interesting. It seems to show that steel screws definity mess things up. The theory with the "shorted turn" is that eddy current flow generates a magnet field that is opposite the filed the produced the eddy currents. That will reduce the inductance even if the conductor has zero resistance and a permiabiltiy of 1. That paper clip is a loop that current my be flowing around inside like a race track. Try opening the clip such that current can't flow in a circle. That is, see to it that the ends of the wire don't touch anywhere and then stick it back in the coil to see what it does then.Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Al, I think it is just the mass and material the paper clip is made of rather than it being a loop. Here the clip has been straightened and cut into two pieces. I separated the two pieces with a sheet of paper. Inductance is increased by the same amount as before when the paper clip was whole. Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 Here is the coil on top of a steel screwdriver. Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted December 23, 2005 Share Posted December 23, 2005 And here, the screwdriver is inside the coil. Bob Crites Quote Link to comment Share on other sites More sharing options...
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