AMSynths AM8109SE (2022)
The Jupiter-8 filter sweep, in a Eurorack case, hand-built in England with the original OTA circuit intact.
Overview
If you've ever chased that velvety low end or the glassy resonance peak of a Roland Jupiter-8, the AMSynths AM8109SE JP-8 Filters isn't just another clone — it's a passport back to 1981, shrunk down to 14HP and wired for modern modular life. This isn't a simulation or a digital approximation; it's a faithful, hand-built analog replication of the actual lowpass and highpass filters from the Jupiter-8 and Jupiter-4, the kind of circuitry that made those synths breathe. And while it’s rooted in vintage design, it’s not stuck in amber — AMSynths updated the signal path with high-quality capacitors and packed it into a sleek black anodized panel made for today’s skiff-friendly systems. Every unit is assembled and tested in Sussex, England, which might not mean much on paper, but to those who’ve opened up a poorly sourced module, it speaks volumes about care and consistency.
This module doesn't try to be everything. It's not a multimode filter, and it won't self-oscillate out of the box, though it can if you tweak the trimmer on the PCB. It aims for a warm, round, balanced tone. The resonance builds smoothly and never gets harsh, creeping up to just before self-oscillation unless you nudge it over. It's based on the AS3109 OTA design Roland first used in the Jupiter-4 in 1980, later refined with Q compensation for the Jupiter-8.
Specifications
| Manufacturer | AMSynths |
| Product Code | AM8109SE |
| Dimensions | 14 HP wide, 35 mm deep |
| Weight | 300g |
| Front panel | Black anodised 2mm front panel |
| Controls | Slide potentiometers for Cutoff Frequency and Resonance; rotary potentiometer for high pass cutoff frequency; small slide switch for filter slope (2/4 poles); second slide switch for envelope CV inversion |
| Inputs | Five 3.5mm jack sockets: 2x audio inputs, 3x control voltages (mod, envelope, keyboard) |
| Outputs | 1x audio signal output jack |
| Included accessories | Set of M3 mounting screws and washers, and a standard Doepfer power cable |
| Filter types | lowpass and highpass filters |
| Lowpass filter slope selection | 24dB/4-pole or 12dB/2-pole |
| Filter core components | uses the AS3109 OTA chip in the filter core, high pass filter uses an AS662 chip |
Key Features
The Real OTA Deal
The AM8109SE runs on the same 2- and 4-pole OTA (Operational Transconductance Amplifier) architecture Roland used in the Jupiter-4. The chip is the AS3109. OTAs behave differently than discrete transistor ladder filters or diode-based designs. They're smoother, slightly softer at the top end, and their resonance has a rounded, almost vocal quality. The Jupiter-8's version added Q compensation, which kept the response balanced as resonance increased and avoided the nasal honk that plagues some designs. AMSynths kept that behavior and changed only one thing: high-quality capacitors in the signal path, for reliability and clarity without altering the vintage flavor.
Sliders That Sing (and Switches That Matter)
The front panel uses vertical slide potentiometers for the lowpass filter's cutoff and resonance, like the original Jupiter. Sliders give instant visual feedback and smooth, continuous control. The highpass section gets a rotary knob, which makes fine-tuning the low-end roll-off a bit more precise. Two small slide switches handle the rest. One toggles the lowpass slope between 24dB/octave (4-pole) and 12dB/octave (2-pole). The other inverts the envelope CV input, which saves you a utility module if you want a closing filter instead of an opening one.
Self-Oscillation — But Not by Default
Some filter modules scream into self-oscillation at high resonance. The AM8109SE doesn't. Resonance increases gradually and hits full effect just before feedback kicks in. If you want it to oscillate, there's a trimmer on the rear of the PCB to adjust. That keeps the module stable in normal use and still gives you a sine-wave generator for tuning or modulation. The original Jupiter filters didn't self-oscillate easily either, and AMSynths kept that behavior.
Built for the Rack, Not the Museum
The module is 35mm deep and 14HP wide, so it fits even densely packed skiffs. The front panel is 2mm aluminum with a black anodized finish. Each unit is hand-built in Sussex and tested before it ships, and it comes with a two-year warranty against defects. You also get M3 mounting screws, washers, and a standard Doepfer power cable.
Historical Context
The AM8109SE is a 2022 revision of AMSynths' original 2010 Jupiter filter design. That first version brought the OTA-based Jupiter-4/8 filter circuit into Eurorack, replacing an earlier discrete design that took up more PCB space. The 2022 update introduced a new faceplate and layout with more sliders and fewer knobs. The core circuit stayed true to the original OTA topology. AMSynths kept the module to a single circuit rather than adding features.
Similar items on eBay
No exact AMSynths AM8109SE listings are live right now — these searches show current AMSynths and similar vintage synth gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.