x0xi0 History

I have worked on TB-303's for a few years and I have always preferred modified TB-303's over stock ones. When done correctly, modifications add to the stock feature set, and a stock unit is simply a subset of a modded version, with no compromise in sound quality. The x0xi0 mod kits started as the result of work I had done on a TB-303 kit. Working with the TB-303 I found very quickly that the limitations of the TB-303 power supply would not allow for additional circuitry without modification to the power supply itself. As a result of a low-power transformer, op-amp based power supply, and battery power, it's very much restricted to passive mods, as there's only a few milliamps available to power additional circuitry.

About the same time as I was developing the kit for the TB-303 I found the x0xb0x community and thought it was a perfect opportunity to design a mod kit with no compromise. Since the x0xb0x community is large and active it would be worth investing time and money into the project, as there would be the potential to sell a fair number of kits. During development I first completed the input & output mods. This included several control voltage and audio inputs and outputs. About this time I also decided to incorporate a flexible overdrive circuit into the kit. The components for these modifications all reside on one small PCB, and as such these mods as a set are generally referred to as the rear panel mods, since the PCB attaches to the rear panel just above the stock x0xb0x IO board. When I finished the rear panel mods I decided to sell it as a subset of what would be the Full mod kit. This is for those that just wanted the flexibility of the additional inputs and outputs, and it also allowed me to make some money to invest back into the development of the Full x0xi0 kit. The first x0xi0 I/O & Overdrive kits were shipped in July 2008. As of January 2012 there have been about (100) I/O-only kits sold.

The remaining part of the Full kit is referred to as the top panel mods, as the new PCB sits just above the stock x0xb0x PCB and includes all the new controls that are accessible from the top control surface of the x0xb0x. It took more than a year to develop the top panel mods. I built & tested many different circuits to decide which were the best to include in the final kit. This included many voltage controlled oscillators, sub-oscillators, low frequency oscillators, envelope generators, noise generators, and other useful mods such linear VCO frequency modulation, several types of filter tracking, etc. I also studied other existing TB-303 mods such as the Devilfish TB-303. The designer of this mod did a very good job with the resources that are available with a stock TB-303, and the Devilfish 303 looks and feels very nice. The x0xi0 Full kit should not be looked at as a devilfish mod for the x0xb0x. The DIY nature of the x0xb0x allows for additional modifications not possible in a stock TB-303, resulting in significant additions such as a second VCO with independent tune and sync, a full VCA envelope generator based on the original TB-303 design, and an additional envelope generator to modulate each the VCF, VCA, and VCO's. All of these modifications are integrated into the stock circuitry and do not change the sound or behavior of the stock unit. There was a unique challenge with the x0xb0x because all of the new circuits had to be designed to work from a single supply. This was more tricky for some circuits than others. After many hours of testing I decided on the final feature set. I included the best & most usefull features.

Like most engineers I'm very particular and I like to do things right, and as such I wanted to develop the mod kits as complete packages. I wanted to include all the parts so that I would have influence over the aesthetics and supply the correct components. The first x0xi0 Full kits were shipped in February 2009. Many of these were Upgrade kits for the original I/O & Overdrive kit. To date there have been about (100) Full kits sold. In March 2010 I completed custom versions of the x0xb0x mainboard and I/O board PCB's specifically for use with the x0xi0 kits. These new PCB's make it easier to install the kits by eliminating several wire connections.

During 2011 the documentation was updated and the new build manuals were completed for those using the Custom x0xb0x PCB Kits. in addition to the kits I have also built several custom x0xi0's to order. This includes I/O Kits, Full Kits, and Custom Kits. At the end of 2011 I completed a design for a complete x0xi0 synthesizer. At this point this product bears little resemblance to the original x0xb0x or the x0xi0-modded x0xb0x, but rather a new machine unto itself. Aside from layout changes to minimize cost and increse reliability the new product also incorporates a new power supply design based on the TB-303. There a a few key components from the TB-303 power supply that are responsible for the sagging 15V supply rail under load. The parts were spec'd and we had them manufartured for us solely for the x0xi0 & future products. This update gives the last bit of TB-303 authenticity, as it enables the same instability or squiriliness you get with a TB-303 under load, such as when playing patterns with high cutoff and high resonance.

---------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------