======= 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\\