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crippledchicken 2nd August 2004 07:46 PM

ceramic cap from rca grounds to circuit question
hi there, my rca jacks grounds and chasis tie together by a trace that runs all across in front of the rcas all the way to the end of the +/- v and circuit ground buss bars which are side by side. and at the end, a screw goes through the end chasis and grounds chasis to this same trace. from there, there is a .047uf cheap ceramic cap which connects to circuit ground buss, which runs back about 3 inches of power supply, as do the other two buss bars. my question is, are there better choices of caps for this type of application. the jacks are also isolated from back plate of the adcom preamp. i guess this cap is to help prevent rf problems. i've heard ceramic worked pretty good getting rid of rf but, being in series with the signal ground, i wondered if there might be a more suited type cap. thanks in advance for any help crippledchicken :)

SY 2nd August 2004 10:42 PM

Ceramic (or some other good RF cap like mica) is exactly what you want here. The function of the cap is to provide RF ground- it's not really a factor at audio frequencies.

crippledchicken 3rd August 2004 12:46 AM

hi sy, thanks for your help i kind of thought maybe that's probably the best type to have there after readind a couple articles on caps but, wanted to get a more experienced opinion than mine. there's also a 10 ohm metal oxide resister which runs from the point where the chasis screw grounds to the rca ground trace to the top side of the circuit board and the whole top of circuit board appears to be one large ground plane. green and all copper underneath. i'l replace the ceramic cap and resistor with new equall components. i'm replacing components a little at a time and upgrading where possible due to age of preamp. thanks again, crippledchicken :)

SY 3rd August 2004 01:26 AM

The function of the 10 ohm resistor is to break up ground loops. It's a pretty common trick- Dynaco used to use that back in the '50s and it wasn't new then. Value and type of resistor aren't very important.

crippledchicken 3rd August 2004 03:51 AM

hey thanks, i've got some metal films of that value i'll use one of them. reguards, crippledchicken :)

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