Federal AM-864/u: 10K resistor across secondary of input xformer?

Sister Ray

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Lately, one of my AM-864/u units started to get a bit more noisy, so I took it out of the rack for a
re-capping job. A year ago, that worked a treat with my other unit.

Now, there are some minute differences in layout between the two units, and most of them I've been able to understand why that might be...
There's one change that I don't understand why it's been made though: A 10K carbon comp resistor has been strapped across the secondary of the input transformer (terminals 4 & 6). From looking at the solder-joint,  that was done either one the original unit, or maybe put in a long time ago, it's certainly nothing recent...

Does anyone know why this might have been done, and/or what the effect is on the function of the compressor? (The impedance of the secondary of the input xformer is already rated at 10K, so I assume the extra resistor will drop the impedance of the secondary to 5.1K, but I don't really get why one would do this).

Regards,

Sister Ray
 

emrr

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10K across sec of a 600:10K simply makes the pri actually be 600.  Someone probably needed a true 500-600 ohm input Z, and that's how they did it.  Take it out.  It'll also load a true 600 ohm source by 6 dB, so it'll also increase limiter input headroom by a bit. 
 

thomasdf

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I was working on a Federal limiter recently. I added a faster release function, and a variable T pad after the output transformer.

It behaves delightfully on my converters, but on many other converters (in different studios) it distorts quite heavily and behaves in a strange way (needs a lot of input level to start compressing, and output level is very loud, even padded to the max)

I believe this is linked to some impedance problems, and I think maybe strapping a 600 ohms resistor across the output will help the problem. Can I also strap a 600 ohms resistor on the input?
I believe modern line levels are more around 10K Z so I was thinking of using a pair of 10K:600 in front and after the compressor, but maybe this is a bit overkill.. 
 

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