AMSynths AM8109 JP-8 VCF v2 (2011–2022)

It doesn't just mimic the Jupiter-8's filter - it breathes like it.

Overview

The AMSynths AM8109 JP-8 VCF v2 is a Eurorack copy of the Roland Jupiter-8 low pass filter, the part that gives that synth its warm, organic voice. It saves you from maintaining a vintage synth. The original Jupiter filter famously refused to self-oscillate. AMSynths changed that, so you can push the resonance all the way into smooth feedback without clipping or harshness.

There are two versions to keep straight. The original AM8109 launched in late 2010 or 2011. The v2 arrived in 2022 with a tighter 10 HP width, red LED slider pots, and cleaner panel graphics. Both are hand-built in Sussex, England, and both use modern components - high-quality capacitors in the signal path, and the AS3109 OTA chip at the core - so there are no 40-year-old parts to gamble on. The v2 is slimmed down for crowded racks but stays faithful to the original design.

Owners report a filter that feels alive - smooth, almost liquid in motion. The 12dB mode (2-pole) is especially praised for its silky, gradual roll-off, and suits pads and evolving textures. The 24dB mode is more decisive, but the difference between the two isn't drastic, which some see as a strength. The Q compensation is Roland's trick for maintaining signal level as resonance increases, and it is faithfully captured here. Cranking up the resonance doesn't make the sound drop out or scream. It just gets richer and deeper until it sings on its own.

Specifications

Manufacturer	AMSynths
Dimensions	10 HP
Depth	80 mm
Front panel controls	Cutoff Frequency, Resonance, level of 2x control voltages, level of 3x audio signal inputs
Jack sockets	Six 3.5mm jack sockets: 2x audio inputs (INA, INB), 3x control voltages (KYBD, MOD, ENV), 1x audio signal output
Filter slope	Can be switched between 12dB and 24dB using a red push button, with a red LED indicator
Filter core component	Uses the AS3109 OTA chip
Current draw	22 mA +12V, 22 mA -12V
Price (original)	£125.00 (as of June 2012)

Key Features

Authentic Jupiter-8 Filter Character

This module replicates the Jupiter-8's low pass filter down to the Q compensation, the OTA-based design first introduced in the Jupiter-4 in 1980. That gives the same warm, musical response that defined early '80s polysynths. The filter's behavior feels organic, not clinical. As resonance increases, the tone thickens naturally, without the sudden drop-offs or instability that plague lesser clones.

Self-Oscillation, Thoughtfully Added

One key change from the original Jupiter-8 filter is self-oscillation. The real Jupiter-8 filter couldn't quite make it to sustained oscillation, but AMSynths modified the circuit to allow it, trimmed to avoid overload or waveform clipping. The result is a smooth, sine-like tone that emerges gradually as resonance climbs, good for clean pitches or eerie drones. It's a small change, but it makes the module far more flexible in a modern modular setup.

Switchable 12dB and 24dB Modes

A red push button toggles between 2-pole (12dB) and 4-pole (24dB) filter slopes, with a red LED to confirm the mode. The 24dB mode delivers the classic, steep cutoff associated with Roland's most famous filters. The 12dB mode surprises people. It's less aggressive and more nuanced, with a "silky" character that suits subtle timbral shaping. The two modes aren't a dramatic shift from each other.

Modern Build, Hand-Tested

Every unit is hand-built and tested in Sussex, England. The v2 uses 2mm thick aluminum panels, either powder coated or multi-colored printed, with improved graphics and red LED slider pots for better visibility in dim racks. The modern, high-quality capacitors in the signal path give reliable, consistent performance and avoid the drift and noise that can plague vintage hardware.

Historical Context

AMSynths launched its Eurorack line in 2010, starting with the AM8060 JP6 and AM8109 JP8 filters. Both belong to the "MODULAR JUPITER" series, aimed at recreating classic Roland filter sounds in modular format. The original AM8109 JP8 LPF was released in late 2010 or 2011, with over 150 units sold by mid-2013. The v2, launched in 2022, streamlined the design into a 10 HP format, which is more practical for modern Eurorack users. The AM8109 covers the low pass filter only. A separate model, the AM8109SE, adds a 6dB high pass filter from the Jupiter-8, so it is a distinct variant rather than a simple update.