Erica Synths and Richie Hawtin’s educationally inspired synth isn’t just for kids.
The concept behind Erica Synths’ Bullfrog synthesizer is an unusual one. It comes from the noble idea that synthesis can be educational. The idea that, behind the bleeps, bloops, sweeps and fizzes, there’s science, art and electronics that can, if given the opportunity, broaden the mind of the child. Everything about the Bullfrog synth is informed by the hope that it will find itself sitting on the graffitied desk of a Year 10 physics student and live to tell the tale.
Bullfrog comes from a collaboration between Erica Synths and electronic music producer Richie Hawtin, who was looking for a way to broaden access to synthesizers through schools. Erica Synths are no strangers to education. Last year, they released a series of educationally focused DIY kits that taught you the electronics behind the modules you were building. Erica Synths’ lead visionary Girts Ozolins was once a high school maths and physics teacher. So, Bullfrog feels very personal, like it holds a lot of expectation and gravitas.
The question this raises for me as a reviewer is whether this is a science project for kids, or if Bullfrog can be a cool synth in its own right. Does meeting the needs of the educational environment make the product better?
Sizeable Hardware
The first surprise is the sheer size of the synthesizer. It’s a proper desktop machine, much bigger than the Eurorack device I was expecting. The modules could be described as being 4U in size, but the synth is spread out and more intertwined than on a regular modular system. It has a one‑piece front panel, so while the signal routing may be modular, the reality of the individual modules is not. I wonder about the reasoning behind the modular/non‑modular choice. On the one hand, the synth is screaming to be taken apart, but on the other, it needs to retain a consistent intention and form if you are going to teach it successfully.
The second surprise is the colour. If Erica Synths is anything, it’s all about the black, and that Eastern European techno vibe. But here we have fun, we have light and joyfulness, we have strong child‑like colours deliberately defining the elements within the synth. The Bullfrog probably wouldn’t look out of place carrying diseases in the children’s waiting area of your local GP surgery. It’s a liveliness that may put off a lot of Erica’s regular customers, but I feel totally drawn to it.
The Bullfrog is fairly substantial, measuring 40 x 385 x 210mm and weighing 1.8kg.
From left to right, we have a full‑range analogue VCO in bold blue, a low‑pass VCF in grateful green and a VCA with an unexpectedly integrated analogue delay in rupture red. To the right we have two envelope generators, and below them a sample & hold circuit. Messing up the ordered lines under the VCO and VCF is a three‑channel mixer in boastful black. At the top is a clock divider; although there’s no clock as such, you can grab a pulse from the sample & hold circuit.
Across the top is an intriguing blue slot. We’ll come on to that later. This leaves us with a volume knob and an integrated speaker in the shape of a bullfrog. The speaker isn’t fabulous, but it’s loud enough and decent enough for classroom shenanigans. Thankfully there’s also a mono output and a headphone output on the back, along with a MIDI In, CV and gate in and a USB socket for firmware updates.
The Bullfrog is big, chunky and dependably solid. It’s great for both the sticky fingers of primary and the barely controlled grapples of secondary. While there is something undeniably toylike about it, this is a serious piece of hardware and the Bullfrog feels like it will survive the most challenging of environments.
The Bullfrog’s rear panel is home to 3.5mm sockets for CV and gate inputs and audio input, a quarter‑inch audio output, a MIDI input and a USB-C port.
Signal Flow & The Manual
The Bullfrog is modular, so if it is unpatched it won’t make any sound. The front panel is very clearly labelled, and all the patch sockets have a direction‑of‑flow indicator that runs along a line to the thing they’re controlling. However, it wouldn’t be immediately clear to a beginner how you’d get something out of it. So, initial modular bafflement pushes you to open the thick and colourful manual.
The manual guides you in choosing between patching the sine or pulse wave outputs to the VCA, or you can take Mix Out from the mixer, which also includes a noise generator, to the same destination. You don’t have to patch directly into the speaker as there are certain elements behind the scenes that make these connections. Otherwise, Bullfrog follows the traditional subtractive routing of VCO to VCF to VCA, with envelopes patched in to control them.
The Bullfrog’s manual is at the heart of the learning experience.
Getting sound from the four available sources takes up four pages of the manual, which then takes you into the idea of plugging in a keyboard via MIDI or CV. It’s nicely illustrated and builds on each patch, taking you through the filter and the VCA before pulling in the envelopes and sample & hold circuit. There are even four patch examples for the clock divider.
I don’t think I’ve ever seen such a great instructional guide to a synthesizer. It’s clear, straightforward and pitched really well at around high‑school age. I’ve already learned a couple of things I hadn’t considered before. The first third of the book covers everything from the nature of sound, pitch and timbre, through to waveforms and harmonics, and onto control voltage, filters and subtractive synthesis. You don’t get to do your first patch until page 29. This thing is thorough and complete without being patronising. It’s not ‘just for kids’; this would be of great benefit to anyone wanting to learn about synthesis.
Peppered throughout are little quizzes which go back over what you’ve learned. They allude to answers and other resources online that are not in place at the time of writing. However, Girts assures me that these resources will be fleshed out once they’ve been pitched into schools. The other thing that’s coming is a huge teacher’s XL version of the Bullfrog. It’s impressively large, I would say a bit bigger than a full‑sized ARP 2600, but with all the knobs and switches scaled up. It has a built‑in oscilloscope, stereo speakers and uses full‑size jacks. You can imagine the teacher using this at the front of the class while the students follow along and experiment on their own standard Bullfrogs. I can also imagine how the room would be filled with the beautiful sound of experimental electronic music.
The other thing that’s coming is a huge teacher’s XL version of the Bullfrog. It’s impressively large, I would say a bit bigger than a full‑sized ARP 2600...
In Use
The Bullfrog squats confidently on your desktop and makes for a very comfortable place to play. The size of the knobs makes you wonder why we put up with Eurorack at all — this is how a synthesizer should be. It’s all spacious and deliberate, easy to navigate and feels fabulous under your fingers. As you fill it out with patch cables, you never get the feeling that you’re lost, hampered or caught up in it all.
It sounds great, like a decent monosynth should. The shaping on the pulse and sine waves is very welcome, and the noise adds to the versatility and provides the sample & hold with something to chew on. The mixer is brilliantly useful in combining waveforms and being clever with dividing oscillations, while the doubling up of CV inputs to both the filter and the VCA gives you the maximum amount of variation and modulation. The filter has plenty of bite and not too much drop‑off as the resonance starts to overwhelm it. Including a delay was a great move. It adds interest and depth to what you’re doing, although it’s not voltage‑controllable.
There are two attack/release envelopes, and they do a fine job. However, because there’s no decay option, you do find yourself duelling the release knobs so the filter sweep can be heard before the VCA closes. On the other hand, they transform nicely into LFOs, have both uni and bi‑polar outputs, and if you plug a cable into the gate input they become independent of whatever you’re playing.
I’m not going to say the Bullfrog is a fantastically innovative synthesizer, but it’s interesting in the way a Moog Mother‑32 is interesting. It’s designed to be foundational and straightforward, and so you will inevitably exhaust the monosynth bass line vibe. However, with a bit of experimentation and a combination of sample & hold, clock division, the wave shaping, delay and the mixer, you’ll find a surprising amount of creative and tonal possibilities. Of course, you can also spill out into other modular synths and systems. But then, if we’re talking about innovation, we really need to talk about the slot.
The Blue Slot
The one bit of esoteric mayhem in an otherwise ordered synthesizer environment is the wide blue slot. The slot is for sliding in Voicecards. Voicecards can either expand the functionality of Bullfrog by adding components, or they can be used as a cool but labour‑intensive method of patch storage. You may have seen something similar on Erica Synths’ PICO System III, but Bullfrog takes the idea to a whole other level.
In the box, you get an Acid Bass Voicecard, a Sequencer, a Sampler/Looper and three blanks for your own patches. Forthcoming cards include an oscilloscope, a high‑pass filter and an electric organ, which gives you a good idea of the range of possibilities.
The Bullfrog comes with a selection of Voicecards but more are available.
The Acid Bass card is a straightforward patch that makes all the connections internally, removing any need for patch cables. Plug it in, and providing the knobs are pointing to something helpful, you should get a nicely resonant bass sound. The Analogue Sequencer keeps whatever patch you’ve made and adds a five‑step sequencer. You’ve got sliders for pitch and buttons to turn the steps on and off. It will run with the sample & hold rate, or it can be step‑triggered using a gate. The great thing about them is that you can plug them in, and you’re off without having to know how to patch the synth together. While that may defeat some of the points of the synth as a learning opportunity, it is immensely satisfying. Any patching you do on the front panel will override anything on the card, so it’s a great place to start experimenting.
The Sampler/Looper is a slightly different animal. The idea is that you can record up to 10 seconds of audio and play it back like a tape machine, or trigger it like a sampler. You can record from the synth or from a built‑in microphone. The recording can be looped or gated, and you can shift it around in speed and pitch with a slider. It has a fabulously lo‑fi and tape‑style feel about it. It interacts with MIDI really well and manages a remarkable four notes of polyphony. On one switch you can engage a ring modulation effect that uses the Bullfrog sine wave as a modulator. It’s all wonderfully mad and rough around the edges. I had some trouble getting it to work as I couldn’t quite grasp how the sound was getting back into the synth. But after a lot of experimentation and reading the manual a few times, it clicked. The kids are going to love this.
If you like a bit of soldering, you’re in for a treat. With a chunk of solder and some wire, you can more or less permanently melt your own patch onto the blank Voicecards. The way I approached it was to build a patch on the Bullfrog with cables, then copy the connections to the card. The only flaw in that idea is that not all the connections were there. In particular, the waveform Mix Out and the individual inputs to the mixer are missing, so you can’t build a patch that combines waveforms. That aside, the satisfaction in soldering your own patch on to a Voicecard is tremendous, and you’ve got three of them. This really should be a standard across all synthesizers. The top half of the card has room for some chips and extra components. There are also power points on the board, which opens up all sorts of development possibilities to people who like to build circuits. I’ll just stick to the patching.
Sticking patches on Voicecards and swapping them out is a wonderful way to engage with your synthesizer. They are hot‑swappable so you can whack another one in right in the middle of a performance. There’s huge potential for interesting developments if you want to dig in deeper.
The Bullfrog has a beautiful full‑range analogue oscillator and a smooth resonant filter with enough functions to make it a useful addition to any set-up.
Conclusion
It’s difficult to separate the synthesizer from its educational intentions, but I don’t think you need to. While it is deliberately simple, it will most likely teach you a thing or two about synthesis. The Bullfrog has a beautiful full‑range analogue oscillator and a smooth resonant filter with enough functions to make it a useful addition to any set-up. Its size and sturdiness make it a delight to use, and its looks would make it a fabulous coffee table talking point.
But it’s the blue strip of possibility that really elevates Bullfrog into something a bit special. The patch saving is brilliant, and I could make cards all day. The included Voicecards brings playful and exciting things to the table, and there’s no knowing where that might go.
Educational Realities
I am married to a teacher, so I have a pretty clear idea about the challenges the educational system presents to well‑intentioned outsiders with their educational novelties. For any off‑piste ideas to fly, they have to be backed up with the right resources so that a teacher can pick them up and teach with them. If it is too complicated or requires them to generate a bunch of lesson plans and learning objectives, then, with the best will in the world, the teacher will ignore the shiny box and run a lesson they are already familiar with to make the best use of that most precious of teaching commodities: time. Perhaps it’s hardly surprising given Girts Ozolin’s previous life as a teacher, but Erica Synths appear to be nailing this aspect.
Pros
- Spacious.
- Sounds and looks lively.
- Superb documentation.
- Sturdy, with a solid feature set.
- Voicecards are ace.
- Perfect for beginners.
Cons
- Too simple for some.
- Not all patch points available on Voicecards.
- Envelopes could be more varied.
Summary
The Bullfrog is a playful and educationally focused synthesizer that offers a clear path to great sounds and interesting expansion possibilities. It’s not just for kids.
