ssm2167 board for compression #ubitx #ssm2167

n8yg
 

I've been reading the topics regarding the ssm2167 with much interest.  So finally I integrated the board into my ubitx v5. I ended up with a trimmer on the output of the board, and pots on the compression, and noise gates.   The problem I ran into is that on the air, rotating the 100K pot I had for compression had little to no effect, but I was getting compression as it was clearly audible on the air. 

I read the data sheet more thoroughly on the ssm2167 and found that the input voltage has to be quite low. -20 to -30 dBV or so.. measuring the electret microphone output on the scope, yielded much higher.. aha..I thought.. I need yet another pot to trim the input voltage. I still needed the 5V to get to the electret so I wanted the trimmer past the 0.1 uF on the board..:-(  so I took of the 0.1 uf cap off the board, and made connections for the trimmer post 0.1 uF cap. So now 3 pots and one trimmer. Trimmer adjusts the output voltage, pots are input voltage to the board, compression and noise gate.   On the air..no compression sounds like no compression.. and turning up the pot makes now a profound difference in on the air sound with a LOT of punch. the Power meter goes way up with compression now. What I believe was happening is that the input was so high that I was in the limiting portion of the transfer curve for the ssm2167, and now I'm back in the linear portion, and all is well!  My problem is that it would really be good to have the trimmers on a board, so maybe I'll design a board to accommodate the changes. 
73
Brad N8YG

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