Synthaholic's FatMan Home Page

Is a FatMan Synth Right for You?

I have two of them and I love the way they sound. I've personally not heard any horror stories, except from one or two people who simply cannot solder or were completely lost with respect to correct part orientation. (IMHO, this is very well covered in the manual, however) It does require that much skill. Other than that, the instructions are flawless and PAiA is more than generous with help and free replacement of any parts delivered in bad or non-working condition.


  • Price. You won't find more bang for the buck.
  • All parts and instructions are included. (not the solder). PAiA is one of the few companies that provides an absolutely complete parts bag. I understand that a few other kit makers also supply all parts and even the solder, but they are also in another price league. The others require you search around for one thing or another. This is one aspect that makes it an excellent choice for those who are just starting out in this.
  • MIDI capable, out of the box.
  • 2 versions: rack (no enclosure, but my favorite) and desktop with enclosure.
  • Very easy to modify. I have many mods installed and most, if not all, are published on my website. One thing though: the desktop box is already cramped, not good if you think you want to have a lot of mods which means more knobs, so panel and interior space becomes an issue. The rack version is standard 19 inch, so additional panels can be added.
  • The stock kit comes with enough 'stuff' to make cool sounds right away.
  • In the event that you *cannot* make it work, PAiA will, for a small fee ($25 I think), fix it for you. This is not true of most other kit companies, (here again, there is at least one other kit maker that also does this for the kits they sell).
  • It's well known and there are many people who can and will help you with problems. Many of them are on the synth-diy email list. There is also a FatMan email list.
  • The parts from which it is made are not rare and are still commonly available from electronics supply companies. They are also still reasonably priced.
  • I don't know about others, but my two FatMan synths are extremely pitch stable. I've been known to leave it off for a few weeks, turn it on, only to find it in perfect tune with the digital synths I have.


  • The FatMan is an analog synth, but it is not patchable (though it can be modified to be patchable fairly easily, there is information on this site regarding this subject). It comes with an internally wired patch. The configuration is set in a traditional basic two VCO to VCF to VCA setup. This is how modulars are used quite often for tonal and melodic music. It doesn't do well for clicks, pops and many sounds normally used in non-tonal noise-scape work. It is possible to add stuff to the FatMan to get it to make more of these kinds of sounds.
  • Pitch CV is linear, not expo. As such, it does not interface easily with most vintage modulars or vintage synths. It is also true that most of the projects and module kits done by people on the synth-diy email list are expo based, so these projects need to be modified to work with a FatMan. However, a pleasant side effect of linear CV is that add-on VCOs are often easier and less expensive to build since there are no transistors to match (or to buy prematched which can be expensive) and no temperature compensation issues to deal with.
  • It is MIDI triggered. That means it won't work with a keyboard that outputs only a control voltage and gate signal unless you modify it (possibly extensively) to do so. However, I think these days, a MIDI studio is quite popular anyway.
  • Odd power supply voltages: +8/-12 (+5 for the uC). This won't be a serious problem, since it's usually pretty easy to convert circuits. All of my mods and all of the ones others have published that are specifically designed for the FatMan are already designed for this, so it's not a big deal.
  • Wall-wart power supply. It is an adequate and noiseless power supply for the FatMan. Mods which require very little or no power can be done without modifying the existing supply or adding a second supply, but larger mods may require an additional supply. The easiest way to do this is to copy the simple and inexpensive FatMan supply, but it means two or more wall-warts instead of one. It hasn't been a problem for me.
  • The kit requires installing a lot of jumper wires and has a flying wire front panel. This is really only a building issue and to some extent, an asthetics issue.
  • Although I've taken mine on car trips to jams, I would not call the rack version of the FatMan completely road worthy. More care would need to be taken with this than professionally constructed equipment that is designed for club gigs etc. It's not that it will fall apart by looking at it cross eyed, but it's easily more delicate than others. I've not seen the desktop model, but I would guess that it's better for the road than the rack model.

As you can probably tell, I'm kind of a FatMan whore. However I do not work for nor have any business connection with PAiA other than being a very satisfied customer.

Mine took about 10 to 12 hours each to build. I've heard that some people do it faster, others slower.

One more thing, I didn't know a whole lot about analogue sound generating and processing circuitry before building the FatMan and joining the synth-diy email list. There is a pretty good 'how it works' section at the back of the FatMan manual. I've also learned a whole lot from the people subscribed to the synth-diy email list. It was and continues to be a great learning experience for me. I now understand a great deal more about voltage controlled oscillators, voltage controlled filters, voltage controlled amplifiers, transient generators, noise generators, current sources, signal processing and many other types of circuits typically found in an analogue synthesizer. I am now able to design my own versions of many of these and I can also now easily modify the designs of others for my own purposes.