Topics

ssm2167 board for compression #ubitx #ssm2167

n8yg
 

I haven't had the feedback problem yet, but am aware of the solution...when it happens...as it probably will show up..
73 Brad N8YG

John (vk2eta)
 

Hello Joe,

Some of us did have that issue and here the link to one solution:

https://groups.io/g/BITX20/message/57047

You can go back up to the  thread level from the post, but be aware I made a mistake in the initial post regarding the resistor value. The schematic is correct.

73, John

Joe Puma
 

Are you getting feedback into your speaker when using this board? I seem to have that problem.

 

Joe

KD2NFC

 

Sent from Mail for Windows 10

 

From: n8yg via Groups.Io
Sent: Tuesday, August 27, 2019 7:51 PM
To: BITX20@groups.io
Subject: Re: [BITX20] ssm2167 board for compression #ubitx #ssm2167

 

Hi John, 
I understand completely. 
The value of pot I chose was 50k, and the adjustment point relative to ground is about 10K.. so 1/5 the voltage output of the microphone. Of course this adjustment is after the cap on the board so that I did not adjust the electret bias as well.. but I think you got that.  I found it difficult to solder to the pads without destroying them, but succeeded finally. I started laying out a board with these mods... but who knows if I'll ever get it done. :-) 

I will caution that I discovered that the noise gate and compression.. seem to have an interaction.. but the noise gate certainly works.. and as my good friend says about the compression now.. "Wow Brad that sounds as good if not better than your 100 W rig at 100 Watts"
BTW thanks for your inspiration for using this chip. It really makes the difference for sure. 
I read your notes.. but was frustrated with the compression making little difference between full compression and none.. Now.. there is a huge difference. 
I hope this helps... I have been hoping someone else would give it a try. 

73,
Brad N8YG

 

n8yg
 

John..if you ate in the same adjustment range i was..i had the same results you are getting..but much better once i lowered the input level.  Anxious to hear about your results.  Thanks for giving it a shot OM.
73
Brad N8YG

John (vk2eta)
 

Hi Brad,

Thanks for the information. 
I should be able to give It a go in a week or so and I'll report on the results. 

Even at the high rate of compression/limiting where mine is at present I get reports of "audible compression, but not unpleasant".

But I would like to soften it a little and have the noise gate work properly.

Thanks and 73, John

n8yg
 

Hi John, 
I understand completely. 
The value of pot I chose was 50k, and the adjustment point relative to ground is about 10K.. so 1/5 the voltage output of the microphone. Of course this adjustment is after the cap on the board so that I did not adjust the electret bias as well.. but I think you got that.  I found it difficult to solder to the pads without destroying them, but succeeded finally. I started laying out a board with these mods... but who knows if I'll ever get it done. :-) 

I will caution that I discovered that the noise gate and compression.. seem to have an interaction.. but the noise gate certainly works.. and as my good friend says about the compression now.. "Wow Brad that sounds as good if not better than your 100 W rig at 100 Watts"
BTW thanks for your inspiration for using this chip. It really makes the difference for sure. 
I read your notes.. but was frustrated with the compression making little difference between full compression and none.. Now.. there is a huge difference. 
I hope this helps... I have been hoping someone else would give it a try. 

73,
Brad N8YG

John (vk2eta)
 

Hello Brad,

Your tests results and analysis explain the results I observed with my SSM2167 module where I had no change when adjusting the noise gate (the Mic sound input was always on).

I would prefer to avoid another trim pot on the module and simply have a two resistor divider after the cap, can you share the value and approximate position of the pot on the input side (towards the Mic element)?

73, John

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