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In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage
Post Subject: Grounding and tranniesPosted by N-set on: 11/24/2011
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 Paul S wrote:
N-Set, why would you disconnect from the house neutral, unless you are using battery power??? This "neutral" is the "ground" leg of your circuit! The house neutral wire is typically white, and the house ground wire is typically green.  The "extra", green, house "ground" wire is intended to be a safety leg, to ground any stray current or shorts. The problem for us is, the house "ground" is typically too noisy for audio, and it effectively winds up working more like an antenna than a real ground. Also, impedance, etc. tend to vary between the house neutral and ground, creating a reactive "noise generator".


Of course I meant "ground" Big Smile sorry

 Paul S wrote:

I am not sure what I would do with all your shielding if I could not bleed/ground it separately (from the circuitry).  Apartments and condos are typically the worst case scenerios, as far as ground noise. If you can trace your circuits back to a real, mechanical gound, try to find a quiet, separate, "un-broken" line to ground for your shields.  It might be a quiet neutral leg of an un-used circuit that makes a "home run", such as a dedicated appliance circuit. This is sub-optimal, but it should help.


At the moment the most stable and quite hum-wise (no idea if this  extrapolates to other noise etc) configuration is signal ground tied to the case.
Lifting this connection (the signal ground--the big Cu plate--floating) in some circumstances catches a horrible magnetic brumm from the PS.

 Paul S wrote:

To damp mechanical vibration it actually sometimes helps to loosen very tight screws to a "critical" tightness.


These are windings unfortunately buzzing, but it's not so bad, from 0.5m one hardly hears anything. I will try to dampen the PS case with a heavy rubber.

 Paul S wrote:

BTW, are you telling me that a Gauss meter reads higher near a smaller transformer (vs, a larger one)?


This is more complex than that. Everything depends on how the tranny is loaded and wound on the primary.
What I meant is an oversized transformer. For example if it's oversized regarding the nominal secondary current (e.g. you tell your winders to wind a tranny for 3x the current you expect to draw from it)  then the magnetic field produced by the actual currents will be lower--the winders use some tables which always assume the highest possible fields to get max out of a given core. If you draw 3x less current, your field strength will be also lower as compared to e.g. a small tranny designed exactly for that current. If you in turn manage to get the primary overwound by e.g. putting 50% more turns than known design tables say (which always assume max B for a given steel), you reduce the field contribution from the primary as well (your B drops those 50%).
This all concerns magnetic fields. Then there are electrostatic fields from the windings, but that's a different story.
Sorry for not offering a clearer explanation...
Cheers,
Nset



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