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

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.