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Topic: Kinoton Dual Basement Reader Question

Pete Naples
Phenomenal Film Handler

Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001

posted 08-03-2014 11:03 AM

Amen Sam!

I remember some years ago a trouble call to Perth Playhouse, a Fedi 35/70 XT projector with a stereo cell and a CP55. The complaint was in optical only surround was working but bypass was OK.

I ruled out Cat222 as it happened in 04 & 05 with the SRA5 installed, by swapping I ruled out Cat150 and Cat243. I was now pretty stumped so in frustration I swapped out the Cat240A for a Cat240 I had in the car. It's now working in 01 but still surround only in 04/05. EH? On the 'scope Cat97 L-R appeared mono'ed with the Cat240A, but OK on the Cat240... Further EH?

So Mono got them through the night and I returned the next morning to do battle once more. After a chat with an older and wiser colleague I looked at the cell wiring.... There was the black wire on the cell waggling in mid air. Some extremely deft soldering with a very fine tipped iron and all was well. I don't think I could solder that now. My eyesight is still perfect but my patience is not.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 08-03-2014 11:36 AM

I thought I explained all of that above? The difference between transformer (isolated) versus electrically balanced systems with differential outputs and the need (or not) for a signal reference.

On a conventional solar cell, the "-" is common to two cells so if it is lifted, you will be using the both cells in series, effectively (think lifting a neutral in an electrical power circuit...you suddenly have 208/240 in a USA system with the loads deciding just how much juice goes to each circuit).

You also don't want to tie the "-" of the CAT240A to ground either.

If you want to feed a line-level source into a CAT240A (or most any other cell input), it is safest to take a PAIR of 47K resistors per channel...even from unbalanced sources use one resistor between "-" and the low side of the line-level source and one resistor between the "+" and the high side of the line level source. The 47K will typically get a 10dB source in the right ballpark on level as well as deal with the active balance input.

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