Modifying dbx166a gate circuit into downward expander

[Mammals]

Hello,
Longtime intermittent reader, first time poster.
I have a number of VCA multifunction compressors, generally from the 1980s, several of which are Symetrix units with, in my opinion, good downward expander functionality--a great help remediating the noise floor issue when I'm using even nice mics and preamps on very quiet sources.
I also have several dbx units, and if it's not an impossible task for a rube such as me, I'd be interested to modify the gate circuits on the 166a, which shunt off sound below the variable threshold, to instead drop off on a steep curve. (As they are, I find the dbx gates unusable, and just leave them off all the time.)
Would there be a straightforward way to modify the existing circuit to accomplish this, or would it instead mean an entirely new circuit, which would probably make it not worthwhile for me to get into?
I am unskilled in this department, but others around me have some skills.
I'll go dig up the circuit diagram if that's helpful. Thank you for your time.

 

[JohnRoberts]

Impossible to say how hard or easy it is without reviewing the schematics. I would not expect it to be simple.

Step one would be to review the schematic of the SKU you want to modify, and then the schematic of one that behaves like you want. After you understand how both work, you can answer your own question, or not.

JR

 

[Bo Deadly]

There are a few different versions of 166a so first you should figure out which one you have exactly and then find the right schematic. Preferably just a link to one in the Technical Documents section if it's there. Is it this one?

https://groupdiy.com/threads/dbx.45603/#post-644189

If I had to guess, I suspect it could be difficult the adjust the timing or adding a timing characteristic to the gate threshold. Anything other than just changing a cap is going to be potentially difficult. You would have to remove parts and replace with a little PCB which means going through the whole process of design, schematic capture, ordering a PCB, etc ... not a good first-post-project.

Also you might crack one open and post some pics. If it's SMD, that creates additional challenges.

Welcome to the list.

 

[Mammals]

This is helpful information--thank you to you both. I'd hoped it would perhaps be as straightforward as swapping in different value resistors or something of that nature, but wasn't counting on being that lucky. That's fine--I can just continue not using those gates. Thanks!