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Quad Eight Electronics EQ712
Quad Eight Electronics EQ712
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Old 11th January 2013, 09:37 PM   #1
PhantomBox is offline PhantomBox  Venezuela
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Join Date: Jan 2008
Default Quad Eight Electronics EQ712

Hello there.
The weirdest thing: my QEE (Quad Eight Electronics) EQ712 sounded great. Is is powered by a 28VDC supply. Suddenly a strong "sss" noise appeared over the signal. After checking the whole circuit inside out (without finding anything...) I finally turned the pot that regulates +28V down to approx. 18.5V(!!!) until this noise disappeared while the signal is still present. As far as I know, + and - rails should be as close together - or equal far away from 0V - as possible.
The EQ is now highly susceptible to outside electrical current draws: when the dryer or microwave oven or the water pump turns on, so does the "sss" noise. And it goes away as soon as the current drawing devices turn of again...

May it have something to do with the 0V connection of my PSU? Or does anyone have a better explanation for this?
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Old 21st February 2013, 09:32 PM   #2
destinystudios is offline destinystudios  United States
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Join Date: May 2008
Default SSSSSSSSSSSSSSS Noises on 712 EQ

Hi there,

Just finished racking the 712 I scored a couple of years ago off evil Bay. Itwas in with a bunch of odd switches, meters, and such and because of the slim nature of the EQ's, They must have thought it was just the Fader portion. Imagine my surprise as I hit the "Buy It Now" as fast as could and prayed. Sure enough, got a pair for $300.00! I do alot of racking and have learned alot about the QEE and Electrodyne equipment I have purchased over time. Ken Hirsch at QEE has always helped me, seems like he is awfully busy these days though. Any, to speak to your problem.

My workbench is only outfitted with a cassette line out for a "line" test signal. as such, it is unbalanced and not a friendly unbalanced when loaded either! To make a long story short, as soon as I got frustrated with all the noise issues I was having, I installed some QEE 3436 input Xfrmers and a couple QEE 3051(I think) output Xfrmers I had been saving, and installed them. Actually quite a bit of work, not to mention close to $350.00 for the Xfrmers, but when I fired it up, sweet unadultrated bliss! NOOOO noise, and my AC in the Garage has fridge motor on the ckt that is on all the time! Just beatifull is all I can say. Even with the EQs flat, just going through the Iron sounds good. I think they werte designed to have Xformer isolation in the first place.

By the way, I have recently found out that these EQ's are 2 of 6 that were on the Warner Bro's Film console in L.A. Talk about history. Hope that helps!

Dan at Destiny Studios
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