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Going Topless

When changing tubes on my ARC preamps, I noticed a substantial lift in performance when the top covers were left off the units. An increase in "Air", 3D and just plain "relaxed ease" was appearent when the covers were off.
Now my particular units have Litz signal wire running from input selector and PC board to the RCA I/O jacks in the back. These bundles of wire come close to the top chassis cover, without actually touching it.
Are we dealing with "Eddy Currents" here? I have come to the conclusion that all (music)signal carrying wires, must be isolated from close proximity to metal. I have heard the same effect on ICs and Speaker wire. All of these wires appear to be well shielded and use a stiff dielectric. There must be stray Magnetic Eddy Currents at work here.
Anyone else go through this? Better yet; Can anyone explain this?
The moral, Metal and wire don,t mix...........Frank
frap
kublakhan
718 posts
 
frap, which arc do you have? can removing the covers be cooling the tubes and causing this effect? do you have tube rings on?
just a thought.
frap OP
213 posts
 
Albert, I never suspected the tubes; that puts a new light on it. Sean is ,of course, correct about the safety and dust factors.
Bruce, I hope you live alone on that one!!!!
Kubla, I run 2 systems. One analog, One Digital
Analog ARC SP-10II, SP-8 Mk-1 preamps
Digital: ARC-SP-3A-1 & LS-2 MkII preamps
I do NOT like the sound with the rings on, It seems to dull the sound somewhat. Now if using the mostly "zippy" sounding Sovtek tube, the rings may help that bad situation.
Dennis, I'm quite certain its the effects of metal.
gregm
3,415 posts
 
Shouldn't the metal cover protect against RF interference? I too have had similarly positive experience with a tube where the manufacturer advised naked if the room was "free of TV and radio interference", and covered otherwise. The sound was invariably better naked (with the occasional taxi CB adding lib to the odd concerto). The idea, as I probably don't remember it, was that the cover created a "farraday trap"(??).

Maybe Sean could throw light on my gibberish?
bob_bundus
1,834 posts
 
A variation on this scheme would be to try removal of the cover & using copper screen as an alternative cover/shield to attenuate incoming RFI (& fingers etc.). This reduces the deleterious effects of signal proxomity to ferrous steel (assuming the cover is steel?) while retaining RFI shielding properties. Or how about making an aluminum cover instead? It would provide less shielding than copper or steel, but would be more easily workable and functional
plato
1,543 posts
 
Bob, I agree that copper or aluminum would both be better alternatives than steel. Interestingly, I have heard from a couple of equipment manufacturers that they use steel in their DACs and preamps because the extra weight somehow equates to value in the mind of the consumer. One manufacturer admitted that he knew his aluminum-cased DAC sounded better than the steel-chassis version; even so, he was reluctant to continue the aluminum version because his customers perceived the lighter weight model as less desirable than the heavier steel version.
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