It is a fine point... a very fine fanatical point. But unlike somethings here, it is legitimate.
It is all about preventing the coupling of electrostatic fields (not magnetic) into the higher input impedance of the next stage. One could argue that, with the cap "reversed", the same noise would just couple through the cap anyway... but that coupling WOULD be more direct... even if just a bit.
And yes, low level high impedance circuits are where you would concern yourself with this.
It is all about preventing the coupling of electrostatic fields (not magnetic) into the higher input impedance of the next stage. One could argue that, with the cap "reversed", the same noise would just couple through the cap anyway... but that coupling WOULD be more direct... even if just a bit.
And yes, low level high impedance circuits are where you would concern yourself with this.
Poobah is right, but this is generally more important where one end is connected to ground. You want the outside foil to be grounded to shield the structure. Next is, as stated, the lower impedance side.
Anything else is open to lively debate. Something to think about too. Suppose you stick the foil side to the input tube on the amp (lower impedance, say 25K) and then replace the high impedance preamp with a low impedance one? It's a silly argument since the circuit layout in that area should have been shielded from noise to begin with.
The above example was extreme, but I have seen it in practice. I guess what I am trying to point out is that circuit layout is more important than foil orientation in low level coupling applications.
-Chris
Poobah, love the 'do too, but are you insured for fire? You don't use hairspray, do you?
Anything else is open to lively debate. Something to think about too. Suppose you stick the foil side to the input tube on the amp (lower impedance, say 25K) and then replace the high impedance preamp with a low impedance one? It's a silly argument since the circuit layout in that area should have been shielded from noise to begin with.
The above example was extreme, but I have seen it in practice. I guess what I am trying to point out is that circuit layout is more important than foil orientation in low level coupling applications.
-Chris
Poobah, love the 'do too, but are you insured for fire? You don't use hairspray, do you?
Hi poobah,
I am starting to think many of use get distracted by some details and lose the big picture.
Sure, some things may make a small difference, but not as large a difference in the grand scheme of things. This is where a good engineer stands out.
Now the hair. I'll bet it's like a veil was lifted from the music! A little sultry and smoky though, but that's your taste.
-Chris
I am starting to think many of use get distracted by some details and lose the big picture.
Sure, some things may make a small difference, but not as large a difference in the grand scheme of things. This is where a good engineer stands out.
Now the hair. I'll bet it's like a veil was lifted from the music! A little sultry and smoky though, but that's your taste.
-Chris
OFF TOPIC...
I actually eavesdropped one day and heard my employees discussing how I would work with a cigarette, smoke it start to finish, and never let the ash fall. They went on... and started plotting... the next day they would try to scare or startle me to see if they could make the ash fall.
Secretly knowing all this, I went to a flower shop and got some of that super thin steel wire they use for flower arranging. I fixed an entire pack of smokes with a thin wire right down the center of each cigarette.
I had the last laugh the next day... a nuclear explosion, and they tried, wouldn't have disturbed my ash!
I actually eavesdropped one day and heard my employees discussing how I would work with a cigarette, smoke it start to finish, and never let the ash fall. They went on... and started plotting... the next day they would try to scare or startle me to see if they could make the ash fall.
Secretly knowing all this, I went to a flower shop and got some of that super thin steel wire they use for flower arranging. I fixed an entire pack of smokes with a thin wire right down the center of each cigarette.
I had the last laugh the next day... a nuclear explosion, and they tried, wouldn't have disturbed my ash!
OFF TOPIC AGAIN...
I played worse pranks on them.
I had a guy that spent three months with a rust bucket '56 T-Bird making the body perfect... and it was... really nice.
The night before the final sanding (ready for topcoat) I took a piece of foam and a hammer and put the tiniest dent in the rear quarter.
I waited the next day until he was sanding that area. From 200 hundred feet across the shop he saw me me squinting... crouched down studying the reflection of the wet surface he was sanding. Told him I could see a little dent. Sure enough, he found the dent... fixed it. I never told him. He never questioned my judgement again either.
I played worse pranks on them.
I had a guy that spent three months with a rust bucket '56 T-Bird making the body perfect... and it was... really nice.
The night before the final sanding (ready for topcoat) I took a piece of foam and a hammer and put the tiniest dent in the rear quarter.
I waited the next day until he was sanding that area. From 200 hundred feet across the shop he saw me me squinting... crouched down studying the reflection of the wet surface he was sanding. Told him I could see a little dent. Sure enough, he found the dent... fixed it. I never told him. He never questioned my judgement again either.
outer foil
The outer foil is marked for applicaions where sheilding is a issue. If they are being used as coupling caps, and neither side is to be grounded, it is pretty much a non-issue. If one side is to be grounded, or at a lower DC voltage than the other, that side should be the outer foil.
The outer foil is marked for applicaions where sheilding is a issue. If they are being used as coupling caps, and neither side is to be grounded, it is pretty much a non-issue. If one side is to be grounded, or at a lower DC voltage than the other, that side should be the outer foil.
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