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In Reply to: If it isn't one thing it's another..... posted by Vinnie on March 18, 2007 at 13:27:27:
Tonight I unplugged both ups units, made sure the cell phones were turned off (they were off last night too)and turned on the system. No buzz at all. Aha, says I, I have found the problem. Just to be sure I turned the ups units back on one at a time. Still no buzz. This has definite potential for making me crazy.
Ideas anyone?
Follow Ups:
Humid/rainy weather sometimes encourages arcing in outside HT lines and such. I've also experienced EMI from airport radar that sounds very much like your description of the noise. Is your preamp totally shielded?
I do get a buzz when my cell phone rings or receives a text message. I used to have a UPS for the computer and it didn't affect the system......like I said before the passive EQ circuit is more sensitive to RFI and perhaps AC induced noises from the immediate environment. Are you using a separate power supply? Through the years I've learned that the best way to keep a preamp quiet is by by building the PS on another chassis.
Hey Joseph
Yep, using a separate ps chassis. The thing that makes me crazy is for it to be there last night and not tonight. I can't think of anything that could have done it unless it was coming from outside the house. I have never heard this particular buzz and pattern before, so maybe you are right about the EQ circuit picking up something. I'll just have to wait and see if it happens again. Any way to shield the EQ circuit?
Vince
> Any way to shield the EQ circuit?
Faraday cage?btw - Put a small HF cap (100MHz something) across the input from the PSU as well.
mvh /Pär
I don't think it is possible, it is the circuit topology that makes it more vulnerable. Kinda' similar to amps that employ negative feedback are quieter than those without.
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