The VCF/VCA 6 is an impressive looking Eurorack interpretation of the VCF, VCA and HPF sections of the Roland Juno 60/106 synthesizers.
The Juno 60 and 106 were different synths but according to SoundForce the topography of the voltage-controlled filters in both machines was identical. Some of the details on this from the SoundForce website are quite interesting:
In the 60 the VCF was built around the IR3109, which was a custom IC including 4 OTAs. The VCA was built with a BA662, another custom OTA chip. The 106 was built using the 80017A, an IC/PCB module including both the IR3109 as well as the BA662. So basically the 60 chips but in a different package. Those were also mounted vertically to save space on the circuit board. The 80017A was tragically dipped in resin during production that caused most units to loose voices as time passed by. Some modern replacements are available and those have been tested during the making of this module.
All those custom ICs are now gone and so they used the Texas Instruments LM13700 and have taken as many components from the original schematics as possible.
You have two inputs with mixing sliders which then goes into the VCF, VCA and finally the HPF to a single output.
The VCF is a lowpass filter switchable between 4-pole 24dB per octave and 2-pole 12db per octave slope. The cutoff frequency benefits from a pair of attenuated CV FM inputs and resonance has its own control and modulation input. You can invert the polarity of FM1 with a switch. A VOCT input provides a musical input to the cutoff which can add to the modulation or play the filter when in self-oscillation. There’s a “loudness drop compensation” switch to boost the low end a bit when the signal drops at high resonance.
The VCA is a regular OTA based VCA with a CV input to control the level.
The HPF is a combination of the filters from the Juno-106 and Juno-60. “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.”
It’s available about now for €289 and you can have it in grey or black. It looks great I have to say, they’ve nailed that Roland look and this is a great addition to their impressive and growing range of modules.
Update: Demo video just arrived!