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. This module is available in both black and grey background colors.
Most Juno users agree that the Juno 60 and 106 are sounding quite different. This is due to many factors: the different base clock frequency of the DCOs, the different SAW directions (falling vs rising), different packagings of the ICs, etc… Hideki Izuchi also mentioned using “a lot of premium parts” on the 60 and “With the JUNO-106, we just wanted to lower its price, whatever it took.”. That being said if you take a look at the schematics you will find that the topology of the VCF in both synthesizers is exactly the same. 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.
As all the original custom ICs are now obsolete and unavailable for purchasing, the popular Texas Instruments LM13700 dual OTA IC was used to recreate the VCF and VCA using modern and widely available parts. All the passives needed have been taken over from the original schematics with some tweaks to adapt this design to the Eurorack format.
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.
Price and availability:
The module will come out in January 2021 for 289 euros incl VAT(238 euros outside of Europe) on the SoundForce webshop and at my dealers. US customers can order directly from Perfect Circuit Audio.