The SoundForce VCF / VCF 6 is a Eurorack interpretation of the Juno 60 / 106 VCF, VCA and HPF sections. It was built based on the original service manuals documentation using modern components.

Signal flow:

The SoundForce VCF / VCA 6 features a simple 2-input audio mixer, a voltage controlled low pass filter (VCF), a VCA and a high-pass filter with 3 fixed cutoff frequencies plus a bass boost position. The signal flow is: mixer -> VCF -> VCA -> HPF.

VCF:

The VCF section is a voltage-controlled low pass filter with a selection between 4 poles (24db / octave) or 2 poles (12db / octave). The travel of the FREQ slider has been calibrated to give you the best experience in the original 4 poles mode. FM1 and FM2 CV inputs can be used to modulate the cutoff frequency of the filter. Those CV signals are added to manual position of the FREQ slider. Note that you can invert the polarity of FM1 using a toggle switch. The VOCT input can be used to close the filter more or less based on the pitch of the note played by your musical CV source. It can also be used to "play" the filter when it is self-resonating. The filter will be in tune across about 8 octaves. Self-resonance is occurring when the RES slider is around position 9 or higher. The resonance can be also voltage-controlled using the Q CV input, this signal is added to the manual position of the RES slider. Please note all CV inputs have attenuators expect the VOCT input.

LDC:

LDC stands for "loudness drop compensation", it is engaged when the switch is in the upper position. This feature avoid the usual input signal loudness drop with high level of resonance. Please note you will need to lower the input signal and / or VCA level to avoid distortion as LDC requires some extra headroom.

VCA:

This section is a "vintage-style" single OTA VCA. There is a manual slider control as well a CV input for the VCA. Both are summed together.

HPF:

The high-pass filter section is a combination of both the Juno 60 and 106 HPFs. Position 0 will give you the bass boost from the 106. Position 1 will not filter at all. From position 2 to 4 will cut progressively more bass and the cut off frequencies are 225 Hz, 339Hz and 720Hz.

Specifications:

18HP
Depth: 38mm (including power connector)
Power: +12V 91mA, -12V 51mA
V / OCT, FM1, FM2: input range -5 to 5V
QCV, ACV: input range 0V to 10V