Review: Kilpatrick Phenol

The Kilpatrick Audio Phenol
The Kilpatrick Audio Phenol

There has long been this promise of an inexpensive modular synthesizer that really never quite gets there. Something is always a little off. Modular synths are complicated beasts, and to really capture the spirit of modern modular movement, looking back is not really the right thing to do. It’s not so much about old vintage synthesizers, it is about bringing in new ideas that are now more common. There is also the additional problem of how to introduce budget conscious musicians to the concept of modular, yet provide them with a window of what is out there.

The Kilpatrick Phenol is taking a shot at this as it provides many of the features of modern modulars in a compact package for under $1000.

Features and Overview


There are a few things the Phenol did right that many manufacturers should pay attention too in the future. The first is the fact the analog oscillators have FM. Why in this day and age is this concept so foreign to those making all in one modular synths? I should note the FM on this synth is so beautiful, everything from bell tones to freak outs. It is an exponential FM circuit, from my experimentation with it, it can achieve some of the more melodic aspects of linear FM.


The much bigger deal is the envelopes, the envelopes are glorious and beautiful. While many manufacturers would be lazy and just throw in a standard ADSR, Kilpatrick went with what is known as a complex envelope. Which means much of the functionality of the device is found with the various options for the envelope. For those like myself who use modular systems extensively envelopes are not ADSR, they are often far more complicated, and the heart of any good modular system. They  take hints from serge and buchla. Make noise in fact literally exploded their business around such an envelope in Eurorack, called “Maths”. In this case Kilpatrick expanded significantly on a buchla style envelope. In fact I would argue for those who own 4U systems, the Kilpatrick Phenol is worth owning for the envelope alone. It is a multi-mode complex envelop with quantization. Yes, you can indeed bring the envelope into a mode to self cycle.  This provides a little bit more depth, as people who use complex envelopes already realize, they are not always going into a VCA, but often end up in a FM input on an oscillator or filter. This is where the envelopes in fact shine on the phenol. It should be noted, much of what this envelope is offering is new and unique. I have not seen some of these features in other envelopes I have had for modular synthesizer.  It is not very often innovation comes in on such a low cost synth, especially an entry level modular, yet here it is.

Truth be told, I think the tutorial covers the depth of the envelopes much better than myself.

Filters and VCA

The filters and VCA’s on the Kilpatrick are good, but a bit more cut and dry. This is one of those things where simplicity was the goal, and achieved. The filters once again have FM, which allows for some fun modulations. One is marked low pass, and the other high pass, even though the high pass one is more of a bandpass filter. These are not crazy resonant filters in the squelchy tb303 territory, they are a bit more refined, and do a more than adequate job for somebody looking to refine a patch using filtering. If you are looking to do searing acid, this is not quite the right filter for that. But it is more suitable for most other tasks a filter can handle.  It is not a self oscillating filter though, and that is kind of important to some.

The VCA’s are pretty simple VCA’s, and frankly, I am not going to dedicate that much ink to them. They do the job, and that is really all one needs to know with this unit.

LFO and Math

The LFO is fairly minimal on its own, especially in combination with some of the other functions. The random provides some standard S&H stepped voltages, and the sine is good for FM with the oscillators and filters.

The secret sauce for the Phenol though seems to be in divider and adder, which has the ability to really make things fun depending on what you plug into it, and where you are sending it, such as throwing it on PWM or an FM unit. The divider can also expand clock divisions for those with sequencers.  When combined with the adder, the results can be a little crazy.

Audio Input and Outputs

Another useful feature is to bring in regular signals into the signal chain. While this may seem a bit odd, this is incredibly useful, especially in live performance context.

The delay has been called a lo-fi echo, but I think it suits the overall module. The mixer also provides a left-right panning function.

Sorry, I did not test midi or the internal sequencer

Here is the part I will be honest with, I have not used the midi to CV converter, or the midi sequencer that comes with phenol. As somebody who uses primarily analog sequencers this functionality is not really something I see myself using much.

Live Performance

I have actually gave this the run through for live performance, and it sounded great in a small environment. The patch leaned more towards sci-fi as supposed to all out drone. Between the Envelopes and Random out I pulled off a beautiful semi-sequenced sound.

The delay ended up being more useful than I first thought, so while it is a bit lo-fi manipulating it can add an extra dimension to the sound. It was a wonderful added feature, which I would be disappointed if it was not there.

Size and Build

The build is solid, there are some choices which I think improve it in fact. Instead of gummy buttons, Kilpatrick went with smaller hard plastic ones. This is something that is greatly appreciated, as it prevents bad presses more than one realizes. Add to it the casing is entirely metal, which means it’s durable.

The one thing to note, is this is thin for a modular synthesizer, it is a little over an inch thick off of a table. I actually was able to put this into a mono laptop bag and was able to go to and from work to a show using mostly public transit. As somebody who lives in a city this is invaluable. While some musicians do appreciate larger setups, for those of us who live in cities, having something small counts a great deal. This is easily the most transit friendly modular that has ever been created. I would also have no issue with being able to fit this into a small carry on suitcase and taking it on a plane.

What Could Have Been Added

If somebody asked me what functions I would like on the phenol, it would likely be a waveshaper, which is an increasingly common function in modular synthesizers. This however is a minor gripe, since overall, the unit is fantastic, and a full voice with a great deal of functionality.  It is a great way to expand an existing serge system, or dive into banana format synthesizers. In terms of the missing ring modulation, oddly enough the adder does serve some of that purpose, and likewise so does the FM on the filters. I could have done without the midi and have had a few more modular features, but this is my own preference. Taking this is an entry level machine, appealing to those who are deep into midi and software, the USB and midi integration makes sense.

Addressing The Banana Synth Cost Issue

I should note, some have griped because Banana synths beyond this tend to be more expensive, but it should be noted 4U has been coming down more in price between more manufacturers coming into the serge space, and Kilpatrick’s own synth format. A typical serge panel would now cost close to $2000-$2500, where with STS it was $4000. Likewise the entry point for kilpatrick format is around $2000 for a small starter system, and per module it is not that much more than a typical eurorack module, and cheaper than many. It should be noted, many starter eurorack synths, are often in the same $2000 price range.

The cost problem with modular is getting off the ground, and this does that, and does that very well with a banana system.  At the same time this is a beautiful complete voice, one where somebody could just utilize this unit alone. For $850 that is a killer deal no matter the format.

Likewise if you want to use a eurorack synth with this, it is not that difficult. A Low-Gain built format jumbler is around $100. This has a ground out, this is really not that hard to integrate with a 1/8 inch jack system. It uses the same 1/v per octave standard as eurorack, so it is just a matter of using the format jumbler with the instructions on Kilpatrick Audio’s site.


This may very well be the best entry synth for modular synthesizers ever created. At $850, it is below the $1000 mark for synthesizers, and frankly, nothing is in it’s category for what it offers. This is a true desktop modular synthesizer panel for the masses.

Likewise by deviating from the east coast style, and going for more west coast functionality such as complex envelopes, and FM at several points, it distinguishes itself from other offerings, and opens up the world of complex synthesis. Likewise with this case this is a full modular and not a semi-modular offering like others in this price range.

This is a nice expansion for those of us who have serge, but is a wonderful starter modular synthesizer as well. It is also a great alternative for those wishing to leave their modular set-up at home, and are more interested in something they can take on the train or bus.

Above everything the Kilpatrick Phenol sounds fantastic. While no synth will ever be perfect, for what Phenol is, it comes very close for a small format modular synthesizer.

Finding Focus, or Why I Left Eurorack

I recently sold my Eurorack Modular System. I needed to take care of some home repairs, and it did help cover the cost involved.

I have missed it far less than I thought I would, and it has allowed me to focus on my other modular system, my Serge format system far more.  This is not to get into a debate of mini-jacks versus banana jacks, my personal preference in terms of format comes more from what I like, not necessarily what is better.  The Serge format panels were ones where I commissioned builders, while the Eurorack was mostly commercial off the shelf units, save for the few I made myself. There was less of an emotional investment as a result.  I am also in the process of building a few serge format panels myself.

Leaving Eurorack removed a level of distraction, and made me focus on my goal. There is though something to be said with modular that rarely does get said, which is the benefits of scaling down ones setup, and refocusing. Over time when using a modular synthesizer one begins to understand what works and what does not in terms of personal workflows and musical (or non-musical) results. The benefits are adjusting along the way. While some do focus largely on novelty, having something that works for one personally is far more important. This is why some people can do beautiful stuff off of a small system.  In my case I am in the position now to know exactly what I want and is the right size for me going forward.

This is not to say I will not one day return to Eurorack, but when I do, it will be from a much different place. One not necessarily of exploration of the format, but clarity. As such it would likely be a smaller system than what I had previously.