SK109-Scale-bias

This module scales the input signal (gain from 0 ~ 1.2) and applies a bias to it (shift it up or down). It works from DC to video frequencies on both the signal and the CV inputs.

It allow s for nice stuff like signal multiplication, luma keys etc.. but is also very handy to get CV-signals into a more useful range.
Note: For better gain lift R215 from ground and connect to negative base of gain pot.

Note: Pushing R307 to 220 Ohms and R308 to 1k8 seems to remove some tendency to oscillate

Note: A negative biased video signal will pull down other channels on the mixer! We should probably add the possibility to clip the output signal between 0 and 1.4V volts, like it’s done on the original sk09-scalebias module.

Parts placement

sk109-place

Module Info

Inputs: – Siff (0-1V)
– Scale (0-1V / -1 – 1V)
– Bias (0-1V / -1 – 1V)
Outputs: Siff out
Power Draw on +5V: 22 mA
Power Draw on -5V: 22 mA
Frequency Response:

Schematic & PCB

View on Github

Parts List

Qty Value Device Package Parts Description
4 3,17/1,1 3,17/1,1 BIAS-IN, GAIN-IN, OUT-, SIFF-IN THROUGH-HOLE PAD
2 CPOL-EUCT6032 CT6032 C10, C12 POLARIZED CAPACITOR
5 100 R-EU_R1206 R1206 R102, R202, R302, R304, R305 RESISTOR
8 100k R-EU_R1206 R1206 R103, R104, R105, R106, R203, R204, R205, R206 RESISTOR
8 100n C-EUC1206 C1206 C100, C101, C103, C200, C201, C203, C300, C301 CAPACITOR
2 10k POT ALPS_RK09L1120 BIAS-POT10K, GAIN-POT10K
1 180 R-EU_R1206 R1206 R308 RESISTOR
8 1M R-EU_R1206 R1206 R113, R114, R115, R116, R213, R214, R215, R216 RESISTOR
3 1k R-EU_R1206 R1206 R207, R217, R303 RESISTOR
1 1k6 R-EU_R1206 R1206 R218 RESISTOR
4 20k R-EU_R1206 R1206 R108, R109, R208, R209 RESISTOR
1 22 R-EU_R1206 R1206 R307 RESISTOR
1 22-23-2031 22-23-2031 22-23-2031 X1 MOLEX .100″ (2.54mm) Center Header – 3 Pin
2 2k2 R-EU_R1206 R1206 R107, R117 RESISTOR
2 2u2tantal CPOL-EUCT6032 CT6032 C302, C303 POLARIZED CAPACITOR
1 300 R-EU_R1206 R1206 R306 RESISTOR
1 47k R-EU_R1206 R1206 R301 RESISTOR
2 4k7 R-EU_R1206 R1206 R101, R201 RESISTOR
2 50p C-EUC1206 C1206 C102, C202 CAPACITOR
1 75 R-EU_R1206 R1206 R309 RESISTOR
3 BAT54S-L44 DIODE_2CACA-SOT23 SOT23 D2, D6, D101 2 Diodes
2 LMH6643MA MAX4392ESA SO08 IC1, IC2
1 LT1228 LT1228 SO08 IC3

Photos


Observations

the “scale” side of things could have some more punch.

Revisions:

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