SSL9K Mic Pre Rotary Switch Resistors ...

[Carl_Huff]

Please don't flame me for this but ....

I am working on a few channels of the SSL9K mic preamp. I want to use 12 pos Grayhill rotary switches in place of the dual 2K5 reverse log pots that sets the overall gain. I seem to remember a thread where somebody worked out the resistor values. Whoever did the work (to my fading memory) actually accounted for optimum noise performance when setting the gain within the stages, but for the life of me I cannot find that thread. Am I crazy??? Did it ever exist? Or should I hang up my solder pencil and retire?? be gentle ....

By the way (if you are interested) the Grayhill part number for a dual deck PCB mount 12 pos rotary switch is #71BDF30-02-1-AJS

 

[jeroddumas]

Here http://www.groupdiy.com/index.php?topic=4731&highlight=


I am gonna put a gain switch in my 9k. But I can't find some of the resistor values so I am gonna get as close as possible. Let me know which set of values you use.

 

[Carl_Huff]

Thank you for the pointer!

My plan is to place resistors in series to derive the right value. I've laid out my own PCB with intention of using a Grayhill 12 pos rotary switch and an optional trim pot. My layout includes a DI circuit that can be switched in and out before the trim pot. The traces for two resistors in series is on the PCB