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======= ssm2164_seppoman pcb introduction =======
seppomans building information;[[ssm2164_pcb]]\\
the following informations are take from the midibox forum, its a collection of infos, without the claim to be 100% true, i will try to test the given information.

====== Shematic ======
not found anywhere... m( \\
also reverse engeniering/understanding/troubleshooting/moding is nearly impossible when the pcbs are stuffed, because most of the traces are on the component site... or hidden behind the black paint\\\
--- first i want to know for what are those POTs? Input Gain of Audio? or of CV? or some BIAS? seppoman said nothing...\\
POT P1 middle & right Pin connected to VCC-\\
POT P1 left Pin connected to a 27K Resistor and this resistor to a nother 27K Resistor which is connected to CV1+ Input. the middle point of this2xresistors is going to the TL74-OP-Amp Pin1 which is a inverting input...\\
The Output of this TL74 Stage is Pin1: its connected to Pin 6 SSM2164, which is the CV-Input\\
When i measure Pin6 to Ground, and Turn P1 most left:1,8V... Turn P1 most right: 2,47V\\
so what does it? no one said: its a zero offset for bipolar cv? or is it gain-control? FIXME m( \\
 

====== Power ======
+ GND - \\
J5 is obviously the only connector where you could come to the conclusion that it might have something to do with power supply.Just like the:\\ 
AOUT(NG), the 2044 board, the MB_FM module etc, **it expects a bipolar power supply of +/- 12 V and GND.
** \\

====== CV ======
as a general rule of thumb you can assume that everything that doesn't specifically mention a bipolar control voltage will expect an unipolar CV. \\
In the case of this module, IIRC the dynamic range of the regular **CV range (0 .. 11.67V)** (uni-polar!) is about 65 dB, with 0V being "silence" and 11.67V being unity gain. \\
I have never thought about what happens if you apply a negative voltage to the CV input...\\
 \\
Note also that generally a bipolar control voltage (CV) still doesn't mean that there are more than two wires involved, \\
just the one signal can be above or below GND.

===== AOUT_NG Connect and Setup  =====
Unipolar Jumpering like shown:\\
{{phatline:MB_AOUT-NG-JUMPING.jpg?850x*}}


===== AOUT_NG Stuffing Parts PCB =====
==== Resistor Solution stock - very low voltage ====
if you followed [[aout_ng]] built plan you will get following Stock-CV-Voltages @+-12V PSU:\\
Uni-Polar CV-Range: 0-11,4V\\
Bi-Polar  CV-Range: +-3V\\

**SSM2164 & Stock AOUT_NG:**\\
As the  SSM2164 is UniPolar, and seppoman designed it as a couple with AOUT_NG. stock is ok\\

**SSM2044 & Stock AOUT_NG:**\\
As the CUT-Off-CV is UniPolar, and seppoman designed it as a couple with AOUT_NG. stock is ok\\
//
I guess for proper +/- 5V operation I'll have to try out a few other resistor values on the SSM module,\\ but this will only apply if you if you're using a different CV source than an AOUT_NG.\\//


**If you need more CV-Range:**
for more distortion, drive, range, or other modules:\\

if you sum two voltages through two resistors of same value, you'll get (V1+V2) / 2 as a result...\\
 \\
==== Resistor Solution low voltage - seppomans prefered ====
**R9...R16 > 5.6k** (only on the channels that are setup for bipolar mode)\\ 
**+-3.5V to +-5.8V** Bi-Polar calibration range\\
**Pro:** easy job, still have a decent precision when calibrating.\\
**Con:** “just change the jumpers if you need some channel in bipolar mode” thought will not work. (FIXME really?)
==== Resistor Solution Stock - -5V Level shifter - NorthernLightX prefered ====
we came to the conclusion that it's probably much easier to have the AOUT only output **unipolar 0 to 10 volt**, and design **a simple -5v level shifter board** that can be used as an add-on (or separate module with hands-on access to the level shifting) to **shift the output to -5 to +5 volt** where needed.\\


**Things to consider are:**\\

- not a lot of equipment actually makes use of negative voltages\\

- equipment that needs bipolar CV input can be retrofitted with a fixed level shifter at the input to make it compatible with your other modules\\

- negative voltages can be used for CV modulation purposes (modulate one CV source with another) so it's certainly not useless\\


==== Resistor Solution high voltage ==== 
**R1...R8 > 10k**\\
**R9...R16 >2.2k** (on all channels).   (QUESTION WHY ON ALL? FIXME)\\ 
**+9.5V to +22V**  Uni-Polar calibration-range\\ 
**+-2.4V to +-5.5V** Bi-Polar calibration-range ( dont think so FIXME)\\
**Pro:** preserve the "just change the jumpers if you need some channel in bipolar mode" thought behind this option.\\ 
**Con:**dramatically increase the calibration range, i.e. exactly calibrating the outputs will get harder because the same angle of turning the pot will have much more impact.\\ 


====== MODs ======
===== MODE Resistor - Noise vs Distortion =====
SSM2164 Pin 1 (the first pin) sets the "Mode"
==== Class AB ====
Pin 1 is Open, no Resistor to +12V (PCB Default)\\
Lower  current results in higher distortion/lower noise.\\
---i do want distortion and dont care about noise--- so i do not change anything, the pcb is fine.
==== Class A ====
Pin 1 is Connected to +12V via a Resistor\\
Higher current results in lower distortion/higher noise\\
lets look in the datasheet:\\
{{:phatline:ssm2164-ab-a.png?600|}}\\
Figures 11 and 12 show the THD and noise performance of the
SSM2164 as the bias current is adjusted\\

I_MODE = ( (V+)−0.6V )/ RB\\
1,52mA = (12V-0.6V) / 7,5K\\
Leaving the MODE pin open sets the SSM2164 in Class AB with 30 μA in the Gain-Core\\
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