AMSynths AM8109 JP-8 VCF v2 (2011–2022)
It doesn’t just mimic the Jupiter-8’s filter—it breathes like it.
Overview
If you’ve ever chased that creamy, velvety resonance of a Roland Jupiter-8 but don’t want to wrestle with vintage synth maintenance, the AMSynths AM8109 JP-8 VCF v2 is your quiet ally in the Eurorack world. This isn’t some vague approximation—it’s a focused, obsessive replication of the Jupiter-8’s low pass filter, the very heart of that synth’s warm, organic voice. And while the original Jupiter filter famously refused to self-oscillate, AMSynths quietly fixed that, letting you push the resonance all the way into smooth, musical feedback without clipping or harshness. It’s like giving a classic car a modern fuel injection system—same soul, better performance.
There are two versions to keep straight: the original AM8109 launched in late 2010 or 2011, and the v2 that 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, the AS3109 OTA chip at the core—so you’re not gambling on 40-year-old parts. The v2 isn’t just a reissue; it’s a refinement, slimmed down for crowded racks but sonically faithful to the original design.
And sonically? 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, perfect for 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: it’s not about extreme filtering, it’s about character. The Q compensation—Roland’s clever trick to maintain signal level as resonance increases—is faithfully captured here, so cranking up the resonance doesn’t make your sound suddenly drop out or scream. It just gets richer, 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 doesn’t just borrow the Jupiter-8’s name—it replicates its low pass filter down to the Q compensation, the OTA-based design first introduced in the Jupiter-4 in 1980. That means 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. It’s not just about nostalgia; it’s about capturing a specific sonic texture that still holds up decades later.
Self-Oscillation, Thoughtfully Added
One key upgrade over the original Jupiter-8 filter: self-oscillation. The real Jupiter-8 filter couldn’t quite make it to sustained oscillation, but AMSynths modified the circuit to allow it—carefully trimmed to avoid overload or waveform clipping. The result? A smooth, sine-like tone that emerges gradually as resonance climbs, perfect for generating 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. But it’s the 12dB mode that surprises people—less aggressive, more nuanced, with a “silky” character that’s ideal for subtle timbral shaping. The transition between modes isn’t a dramatic shift, but a refinement of intent: one for precision, the other for warmth.
Modern Build, Hand-Tested
Every unit is hand-built and tested in Sussex, England. The v2 version 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 use of modern, high-quality capacitors in the signal path ensures reliability and consistent performance, avoiding the drift and noise that can plague vintage hardware. It’s a boutique build with a purpose: to deliver vintage tone without vintage headaches.
Historical Context
AMSynths launched its Eurorack line in 2010, starting with the AM8060 JP6 and AM8109 JP8 filters—both part of 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, making it more practical for modern Eurorack users. While the AM8109 focuses on the low pass filter, a separate model, the AM8109SE, adds a 6dB high pass filter from the Jupiter-8, making it a distinct variant rather than a simple update.
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