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In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage
Post Subject: Grounding, tarnnies and diodesPosted by N-set on: 11/24/2011
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 Paul S wrote:
If you can do it, try isolating both cases/chasses from your "ground plane(s)". Use one inclusive "ground plane" for both the PS and the gain/RIAA sections, and ground this "ground plane" to the house "neutral" wire. Do NOT connect any shielding to the "ground plane". Then ground the cases/chasses, all internal shields, the IC shields, TT/motor, arm and step-up ground lugs to a special, dedicated ground rod (not the house neutral or ground!). This special ground rod is the "bleeder" I keep referring to.


Paul, thanks for a valuable input!
Unfortunately I'm unable to do it--apartment on a 6th floor...city center... Sad I plan to disconect
from the house  neutral at all once I'm sure the equipment will not kill me. But the hum I have
is 99% an air pickup, not the hum enetering from the grounds.

 Paul S wrote:
If you have noise from the bridge, consider using the (Fairchild?) "Stealth" diodes; they are VERY quiet. I posted about these in my K&K thread.


What are they? I use those en vogue Cree SiC's. When I have time and motivation I'll experiment with adding
a 10nF C accross the diodes to soften the tranny kick-back...in principle this antique technique should be
 redundant with SiC's...so the advertising slogans say.

 Paul S wrote:
Maybe the above will work to quiet your rig. The big, strong trannies throw big, strong "fields", however, and they do tend to make their own problems. Surely you have the trannies on isolation pads of some kind, with fasteners tightened "just so", to quell vibration, and tranny axes at right angles when they are adjacent?


...and here we eneter a minefiled. Tha tranies are adjacent but the axes are parallel....I had no other choice
to place them. I'm considering an attempt to individually pot them in a steel tomb.
Size matters, the theory says oversized tranny=lower magnetic fields=lower emission
(at least due to the fields generated by the currents in the secondary; this is what one
usually can easily control when ordering trannies; making transf. winders oversize the primary is a lost battle).  
The vibration I get is probably due shitty made windings. The isolation for the chassis is tip-top (thick silicone,
nylon tight screws, alu base, etc).

Cheers,
N-set





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