Back when Dwyfor Tech first launched I made a video with their first module Pas-Isel, it was a pleasure to learn more about the circuit design as it had interesting stories of ‘forgotten Buchla filter’ and it was clear Dan (from Dwyfor Tech) was looking into lesser known circuits, synth history and combining things to create interesting circuits and modules with their own sound and behaviour.
Since then he’s launched a Yamaha mono-stereo expired patent exploring phaser/band pass and notch filter module and today he’s just released Cryfder a dual VCA with a tube saturating mixer stage. So I asked him some questions for another instalment of STORY TIME!
Ben // Dan, it’s a pleasure to be chatting to you again some time after your first release as Dwyfor Tech ‘Pas-Isel’ (which we had an interview about HERE and demo video HERE). How was launching the company? What was the reception for Pas-Isel like for you?
Dan // Hi Ben, lovely as always to talk with you! I’m very glad to say that since Dwyfor Tech launched in early 2024, I’ve had a lot of really positive feedback about what I’m making. It’s amazing to me that we’re this far along and I’m still selling Pas-Isels! It’s taken me to Machina Bristronica twice, invitations for collaboration with others, and opened up a whole new friendship network for me that I simply didn’t have before.
Ben // Following on from Pas-Isel you released Deuawd, what led you to phasers and what’s special about that one? I’m sure you’ve stories of its origins and features to share with us.
Dan // So that was an interesting one. It started with reading an expired Yamaha patent for creating a pseudo-stereo output from a mono source, based around a static phase shifter, and that inspired me to think about how to get a similar mono-to-stereo adapter working in Eurorack. In a way, it’s a Pas-Isel adaptation, as it uses the same voltage control scheme with diodes and a differential CV, but with some tricky quasi-mid-side circuitry on the outputs. It’s pretty similar to the diode phaser in the Steiner-Parker Synthasystem, but that’s by accident, I only found out about Nyle Steiner’s design afterwards!
Deuawd is unique in that, without any feedback, it’s a perfect spectral splitter (what’s missing on one output compared to the input will be the only sound present on the other output), and so it unlocks a lot of interesting frequency-based processing options and stereo effects. It also has attenuverting feedback, which affects each output differently and makes for some interesting resonance options.
Ben // One thing that’s been nice to see with all the modules is that you develop these publicly, out in the open as it were. Can you speak to how that works for you typically? Is it a desire to share? Learn & contribute to communities and the spaces you find yourself in?
Dan // Yeah, I think a lot of it is just a deep love for what I do and wanting to share that with people. I get very enthusiastic about coming up with a new design, I find it hard to keep it just to myself! There’s no real open source license or anything like that, I just like sharing my passion.
Ben // One thing I remember from the Pas-Isel release was the call for assembled modules, other than an offer to assemble a module – built to order – you stick to DIY kit or panel/PCB releases, what was the draw to DIY and the decision to work in that format near exclusively?
Dan // I’ve always been a huge fan of historical electronics DIY, such as schematics in magazine articles and educational kits. Radio Shack, Maplin, Heathkit, and so on, or for synthesizers specifically, companies like PAiA and Powertran. A lot of it is the desire to try and bottle the feeling of building a PAiA 4700 module, or a noisemaking gizmo from Wireless World magazine. That’s why about half of my product build manuals are educational material on how the circuit works! And also why I include a free teabag with each kit, to give you something to enjoy on your mid-build break.
Ben // We should say you’ve been working with Thawney to offer some assembled versions of your modules, how did that come about?
Dan // Robin lives locally to me and we hang out every so often. They set up a fantastic service called South West Synthesis, which provides PCB design, product fabrication and marketing/distribution services for synth and pedal designers in the region. An SMD re-working of Pas-Isel was the first SWS product, and now can be found on shelves in Elevator Sound and Nightlife Electronics. It’s a partnership that’s working great so far!
Ben // All of this leads us to the latest release, which has been a pleasure to work with you on, which is Cryfder – a dual VCA with flexible controls and a tube saturating mixer stage. With the interesting developments for the other modules in mind – why bring this to life? What makes it different to what’s out there?
Dan // A good amount of it was, as with Pas-Isel, frustration with current designs of similar modules. I love valves, and have been designing valve circuitry for a good few years. A lot of modules use current production valves such as the ECC83 (12AX7 in American numbering), but to do so in Eurorack would require running the anodes at a tenth of what they should be, at most, and the filament draws a tremendous amount of current. I wanted to make a valve circuit that was designed for Eurorack from the ground up: Ultra-low current draw, compact, and with a datasheet anode voltage much closer to what can be achieved in Eurorack. I think I’ve managed to do that with a DM160 (6977 in American numbering), a late ’50s VFD indicator lamp that draws only 30mA on the filament (all on the negative rail in Cryfder), and is only around 2.5cm tall.
The VCAs are based around discrete diodes and use the same voltage control principle as in Pas-Isel and Deuawd, in keeping with Dwyfor Tech tradition. Now this is a real rarity in synths in general; the only diode VCAs in production synths are very early Korg offerings such as the MiniKorg 700, 770 and MS50. You also find them in Neve compressors, with balanced transformers. The Cryfder design is an adaptation of an idea from Rod Elliott of Elliott Sound Productions. Being diode-based, they soft-clip in an almost triangle-to-sine kind of way if you turn up the input gain – I like to say that, even bypassing the VFD, they’re ‘tubey by default’. They also resemble the VCA in Moritz Klein’s compressor, but that’s another happy accident, I only learned about that design afterwards!
Ben // What was the development of Cryfder like? Any simpler or more complicated than the other designs?
Dan // Would you believe that early development of Cryfder was concurrent with Pas-Isel? I’ve really been working on it that long! And safe to say, it’s been a bit of a journey. The first prototype of Cryfder was a very, very different beast. Also a dual VCA with valve mixer, but based around a vintage Philips balanced modulator IC, and with a Big Muff tonestack wrapped around the valve… I hated it. I spent weeks developing it, just for the actual module to sound boring. The VCAs were totally clean up to the point they hard-clipped. The tone control did nothing despite making rather dramatic shapes on the oscilloscope. I learned a lot from that, not least not to be afraid to give up on a design. Just about the only thing the final module shares with that first prototype is the name and the VFD.
Ben // What are some of your favourite uses for Cryfder? Or you other modules? Any special “combo move” unlocked when using all 3?
Dan // Because of the internal normalling, it’s trivially easy to configure VCA 1 as voltage-controlled resonance for Pas-Isel and VCA 2 as a final VCA post-filter (with optional valve drive). I include a guide on how to do this in Cryfder’s manual. Because the resonance path is different, it does have a different character to it too. With Deuawd, it’s a great panner, adding yet another stereo modulation to liven up the sound. It can also be a very characterful recombinant mixer, letting you use the two modules together as a valve-based voltage controlled parametric EQ.
I also quite like sticking things in the feedback loop around the valve and making things that don’t normally oscillate do so. Waveshapers become white noise generators, delays and filters become oscillators. I also love just using the valve stage as distortion on a really resonant filter. What can I say, I’m a simple man, I like a bit of classic acid!
Ben // So what’s coming up next for Dwyfor Tech? Anything you can share with us here?
Dan // I’ve got a working prototype of a VCO on the go at the moment, that’s inspired in equal parts by the Yamaha CS80 and Rhodes Chroma, called Gwraidd (which means ‘root’, as it’s the beginning of the signal chain). Like other Dwyfor Tech modules, it’s designed to have a relatively conventional feature set, but goes about its job in a totally unique and unexpected way behind the panel, imparting its own flavour and character on the sound that you can’t get elsewhere. It’s got other goodies too, such as a discrete PWM circuit, LFO mode button, and the filthiest hard sync I’ve ever heard. All designed with a minimal parts count, all off-the-shelf and nothing obscure or proprietary.
I also am working on a successor to Pas-Isel, named Eryri, which will add extra filter modes to the same core, with some subtle and sympathetic upgrades added as I go. That’s early days right now, though.
Ben // Did I see somewhere you were working collaboratively with someone too? Who and what was that?
Dan // More than one! I’m working with MEGA Modular Corp. on a percussion synthesizer module based on a Soviet Latvian drum synth, that was shown off at the last Knobcon, and with Thawney on a DCO based on the VCO from the Roland Jupiter-4 and ProMars. There’s a bit more too, but I’m not sure I’m at liberty to say too much right now!
Sound Workshop also selected Pas-Isel for the filter in their excellent drone synth Quord, and I’m doing a little freelance consulting for them to adapt the design to fit their needs.
Who knows what the future may hold, though? I think it’s the connections and sharing of ideas that really makes the Eurorack maker community, and I’m so happy to be a part of it.
Ben // One thing to end on, that I feel some people around the world maybe wondering, where does the company name and the modules names come from? True historic or playful Welsh naming is it?
Dan // Starting with the module names, I try to keep them quite descriptive of what the module actually is. Pas-Isel (pronounced as ‘pass is-elle’) means, well, low pass. Deuawd (pronounced ‘day-owd’) means duet, and alludes to the fact there’s two outputs that work together in unison. Cryfder (pronounced as ‘cruv-dare’) means strength, and hints both at the small but mighty valve distortion and the fact that it controls the audio output strength.
Dwyfor (pronounced as ‘dwee-vore’) is the name of a river in North Wales, and also the surrounding region, where both me and my family are from, even if I haven’t lived there in many years now for a variety of reasons. Members of my family also hold the title of Earl Lloyd-George of Dwyfor, a hereditary title of the region.
The coast between the rivers Dwyfor and Glaslyn has been a fundamental cornerstone of my life. It’s my family home, the core of my childhood, the root of my history, the focus of my hiraeth. It’s a special place to me, and I’m glad I’m able to honour it in some way.
Ben // Thanks to Dan for taking the time to chat to us, it’s a pleasure to not only work on demo videos but bring out some of the stories, development process and the people behind the gear too.
Dwyfor Tech DIY kits, PCBs/panels and modules built to order are available from Dwyfor Tech Directly on
Reverb // https://reverb.com/uk/shop/dwyfortech
Etsy // https://www.etsy.com/shop/DwyforTech
