DOEPFER MUSIKELEKTRONIK GMBH
ANALOG MODULAR SYSTEM A-100
A-126 Voltage Controlled Frequency Shifter
Service Manual
Adjustment of the multipliers:
Y1 and Y2 are jumpers, X1*Y1 and X2*Y2 are test pins on the A-126 board
• middle position of the frequency knob (i.e. about 500Hz frequency shifting, exact frequency is not
important)
• no audio signal at the audio input (or input level = zero)
• install jumpers Y1/ST4 and Y2/ST3
• connect the single pin X1*Y1 to scope and/or mixer/amplifier
• adjust trimming potentiometer Y1 Bal. for minimum signal appearing at X1*Y1
• connect the single pin X2*Y2 to scope and/or mixer/amplifier
• adjust trimming potentiometer Y2 Bal. for minimum signal appearing at X2*Y2
• full audio signal just before clipping at the audio input (e.g. a 500 Hz sine wave from a VCO or VCF in
self resonance, exact frequency is not important))
• remove both jumpers Y1/ST4 and Y2/ST3
• connect the single pin X1*Y1 to scope and/or mixer/amplifier
• adjust trimming potentiometer X1 Bal. for minimum signal appearing at X1*Y1
• connect the single pin X2*Y2 to scope and/or mixer/amplifier
• adjust trimming potentiometer X2 Bal. for minimum signal appearing at X2*Y2
repeat all adjustments for best results (i.e. minimum signal, less than 10mV are possible for ideal adjustment)
VCO Offset
VCO Scale
Y1 Balance
X1 Balance X2 Balance
- Adjust
Y2 Balance
+ Adjust
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