AM8109 JP8 Filter


2018 Module

Overview  This module is replica of the Low Pass Voltage Controlled Filter from the legendary Roland Jupiter 8 and 4. This is a 2 and 4 pole OTA design that Roland first used in the Jupiter 4 in 1980, replacing a discrete version of the filter which took up more PCB space.

This is a warm sounding filter with smooth frequency control and a resonance that gradually increases up to full self oscillation, a sound very reminiscent of the early 1980′s. The difference between 2 and 4-pole modes is not dramatic, with the 2-pole mode providing a more gradual cutoff slope and silky sound. We launched this filter in 2011 and have sold over 100 since then.

Euro Rack Module: 14HP wide
User Manual: Download PDF

Detailed Description This module is an accurate reproduction of the Jupiter 8 low pass voltage controlled filter, using the original IR3109 OTA chip in the filter core. The design has been updated to use modern components (such as OTA capacitors and high quality Op Amps). It delivers a very warm and smooth sound.

There are front panel controls for adjusting the Cutoff Frequency and Resonance as well as the level of 2x control voltages and 3x audio signal inputs. Resonance is smooth and controllable self-oscillation. The slope of the filter can be switched between 2 and 4 poles using a small red push button, and a red LED with lens shows the filter slope selected (12dB or 24dB).

PCB Kit – a PCB and kit of hard to locate components is on sale in our Online Shop if you have an IR3109 and wish to build this module.

Original IR3109 VCF Chip

Potentiometers:

  • Cutoff Frequency
  • Resonance
  • CV1
  • CV2
  • 3x Signal Levels

Connections [3.5mm jack]:

  • Signal A, Signal B, Signal C
  • CV In 1, CV In 2
  • Signal Output

Power:   Standard Doepfer 10 way cable to 16 pin power bus
Front panel:   Machined out of 2 mm aluminium and colour printed
Dimensions:   14HP width, standard 128.5 mm Euro Rack height, 80 mm depth

Sound Demos

AM8109 V2 Rear

Availability The AM8109 was redesigned in January 2019 to be skiff friendly with two PCB’s parallel to the front panel. The depth of the Version 2 module is now 35 mm and its far easier to build with no wiring required. The jack sockets have been upgraded from Cliff to Erthenvar with custom stainless steel washers that we have had manufactured. An initial small run of 15x completed modules using Roland IR3109 chips was available in 3Q2019, along with panels and PCB sets. The panel and electronic design is the same design as Version 1.

Analog Renaissance released a clone of the IR3109 in June 2019 as the AR3109, details are here. AMSynths have had early access to the first AR3109 chips, and we have tested them in the AM8109 and found them to be perfect. The availability of this clone chip means we can continue to manufacture the AM8109 module and DIYers can easily build our PCB kit. We are unlikely to build any further modules using the IR3109.

Copyright AMSynths 2017