AMSynths AM-CP3 (2020s)
A four-channel transistor mixer that clips the way vintage Moog mixers do. It sits quietly in the voice stack of a modular.
Overview
Plug four oscillators into the AM-CP3 and turn them up. When the signal gets too hot, it collapses softly, which is rare in modern Eurorack. It isn't a limiter and it isn't a digital safety net. The transistors are being asked to do a little more than they were designed for, just like the original Moog CP3 from 1967. The module does the unglamorous job of summing VCOs before they hit the filter, but it shapes the sound of the whole patch. The clipping isn't harsh. It adds a low-mid grit that fattens thin waveforms and rounds off the edges of pulse waves, and it sounds more alive than a clean op-amp mixer.
AMSynths didn't just clone the CP3. They reworked it for Eurorack. The AM-CP3 is a 20HP module, which gives it room on a crowded panel. The gain pots sit vertically and the input jacks are clustered at the top, so patch cables from the VCOs stay short. It's meant to sit right after your oscillators, which cuts cable clutter and signal loss. A "Click Filter" switch engages a 1μF polyester capacitor on each input. That can smooth out fast CV transients, like the nasty pops when you switch waveforms, or act as a gentle high-pass on audio signals. The original never had it.
There are dual outputs, normal and inverted. That opens up phase tricks, and they're handy when feeding multiple filters or building stereo imaging in a modular rig. The trunk line architecture comes from Moog's console systems and is kept here, with buffered send and return paths. You can route the mixed signal out to external gear, like guitar pedals or outboard compressors, and bring it back at pro audio levels. The internal gain is set to 0.5x by default, so a typical Moog VCO's ~10V peak signal gets scaled down to +4dBu. That suits studio gear without overloading its inputs. Most mixer modules don't bother with this.
Specifications
| Manufacturer | AMSynths |
| Production Years | 2020s |
| Format | Eurorack |
| HP | 20 |
| Depth | Not specified |
| Current Draw | Not specified |
| Channels | 4 |
| Input Type | Audio / CV |
| Output Type | Normal and Inverted |
| Gain Structure | 0.5x (trunk line out) |
| Click Filter | 1μF polyester capacitor per input (switchable) |
| FX Send/Return | Buffered, level-adjustable via potentiometers |
| Routing | Front panel gain pots, ON/OFF slide switches |
| Multiples | 4 interconnected jack sockets |
| Construction | 2mm black anodized aluminum panel |
| Weight | 350 g |
| Power Cable Included | Yes (Doepfer standard) |
| Mounting Hardware | M3 screws and washers included |
Key Features
Transistor-Based Mixing with Musical Clipping
The AM-CP3 uses discrete transistor circuitry instead of op-amps for its mixing stage. A clean summing amplifier stays sterile. This one saturates softly when driven hard. It isn't distortion in the modern effects sense. It's a gentle rounding of the waveform that adds harmonic complexity, and it's part of why early Moog systems sounded so full with just two or three oscillators. You could reach for a distortion module to add grit, but here it happens in the signal path. The clipping is subtle enough that it won't dominate a mix, but you'll notice it missing if you switch to a transparent mixer. It works especially well when layering sawtooth waves or pulse waves with PWM, where the slight compression smooths the transitions and glues the sound together.
Integrated FX Loop with Level Matching
Most modular mixers treat external effects as an afterthought, if they handle them at all. The AM-CP3 has a fully buffered FX send and return with front-panel level controls. You can patch in guitar pedals, compressors or reverb units without worrying about impedance mismatches. The send level is set with a pot, and the return path has its own gain control, so you can set the wet signal's volume before it rejoins the mix. The trunk line buffers work with both -10dB consumer gear and +4dBu professional equipment, which is rare in Eurorack. The rear PCB has connections for mounting external jacks, so you can wire it to side or rear panel outputs for a permanent setup.
Click Filter and Phase Control
The Click Filter is a small feature that does a lot. Flip the slide switch and a 1μF cap goes in series with each input, blocking DC and attenuating low frequencies. On CV signals, this removes the sharp transients that cause audible pops when switching waveforms or modulating pitch. On audio signals, it acts as a high-pass filter around 160Hz (depending on load), which can clean up muddy oscillator stacks. It doesn't replace proper DC blocking elsewhere in your system, but it's a fast fix in the middle of a patch. The dual outputs, normal and inverted, let you experiment with phase cancellation. You can feed both outputs to separate filters or blend them in an external mixer. That can give hollow, phase-shifted tones for experimental textures or pseudo-stereo effects.
Historical Context
The original Moog CP3 was part of the 1967 Moog Modular lineup. It appeared in Models I, II, and III, in both console and portable versions. It was the central mixer for VCO outputs, routing them to the main filter and amplifier sections. The CP3 wasn't flashy, but it was essential, because it was where the sound was first assembled. Moog used passive trunk lines (internal front-to-back signal paths) to reduce cabling and keep the signal intact. AMSynths has kept that concept and updated it for modern needs.
In the 2020s, Behringer's System 55 brought affordable Moog-style modulars to a wider audience. That left a gap for console panel modules to complete the system. The Behringer CP3A-M was a functional clone, but AMSynths saw room to improve on it. The AM-CP3 adds an FX loop and dual outputs that the original never had. It fits a wider trend of boutique builders reworking vintage designs with modern usability in mind.
Collectibility & Value
The AM-CP3 is a new production module, so it isn't "vintage" in the traditional sense. Even so, it's already sought after by Moog modular enthusiasts and Eurorack builders chasing 1960s/70s tone. It's sold directly through the AMSynths web store in limited batches, which keeps it scarce on the secondhand market. As of 2026, the new price is £129 (including UK tax). There are no known units on the used market yet, likely because demand exceeds supply and owners aren't eager to part with them. Given its niche appeal and build quality, it's unlikely to depreciate, and if production ever stops, it could become a minor collector's item among Moog replica builders.
There are no known failure points specific to the AM-CP3. As with any transistor-based analog circuit, long-term reliability depends on component quality and operating conditions. The module comes with a two-year warranty from AMSynths. One practical note: the external trunk line jacks are not included and must be purchased and installed by the user. That isn't a flaw, but it's an extra step. You'll need to source 3.5mm jacks and do some light soldering if you want to use the FX loop with rear or side panel connections. The module ships with screened cables for internal trunk line linking, so basic operation works out of the box.
The main question for buyers is whether they need this over a standard Eurorack mixer. If you're building a Moog-style system, especially one based on Behringer's 900-series modules, the AM-CP3 fits both in function and in looks. If you only want a four-channel mixer with some grit, there are cheaper options, but none that copy the CP3's specific mix of utility and vintage coloration. It's not a must-have for every rack.
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