The behavior of the 610 is like no other compressor/limiter in that the dynamic range seems to be what triggers comp vs. limiting vs. both. Perhaps the stereo link is doing its thing? Below is how the newer units describe the link condition, which seems to imply a different type of link than other compressors use. Maybe contact the company, which is still in business to see if they have changed the circuit for the link function over the years. The current units use a TS jack to link units and no special stereo adapter is required.
"Stereophonic Operation
The interconnection couples the attack and release action of the limiting and compressing functions of the two units. The input
(compression/limiting) and slope controls on either unit may be independently set for the desired mode of operation. However, when
the attack action of either unit is activated, the other will follow so as to maintain the stereophonic perspective. The release action will
follow the fastest setting on either unit. Prior to differing applications, the accessory may be switched in or out of the circuit as
desired.
¼” TRS cable required for two channel operation."
I don't have factory 610 units, I bought an old quad SS console in the mid 90's that was falling apart for $500 I think.
I pulled all the cards, EQ's, trannies, meters, etc and sold off most the parts keeping just enough trannies and cards for a pair of preamps and I kept the 4 601 and 603 cards along with enough parts to utilize the compressors.
Oddly enough the console had the 4 compressors hardwired to the quad buss with no type of link for them, the console was custom made and not a factory design.
I actually visited SS in Ogden when Dilley was still alive...he wanted nothing to do with me! I did buy the accessory which is just a 5.6uf non polarized film cap.
I eventually built a pair of 2 channel rack units, at one time I had all 4 in one giant old rack I threw together from bits dug out of DA audio in SF...a real beast.
Engineers tell me mine sound cleaner than the factory units but everyone that uses mine loves them.
I saw(and see) no use in duplicating the threshold and overload indicator circuits, at least not for me.
But if I were duplicating the 610 I would not go with the individual card layout they used originally...it's a total pain to wire up and come up with a support system for the cards and all the point to point wiring involved but that's just me...I've wired all 4 up twice and I hated it more each time!
Good luck
