The Open Amiga Sampler Cart Brings Inexpensive 8-Bit Audio Sampling Back to the Masses
New DIY dongle helps demoscene devotees, chiptune aficionados, and retrogaming enthusiasts recreate authentic 8-bit sounds on a budget.
"Why buy an ordinary sound sampler — when you can buy a recording studio?" asked a 1991 advert for the New Dimensions TechnoSound Turbo — a marvelous piece of kit which transformed the already extremely capable Amiga into a near-pro-level audio workstation. While the "revolutionary" notion of owning your own sampler for 35 quid vs. paying £100s for professional studio time — or £1000s for an Akai S1000 — may seem quaint in 2020, when everyone has access to a vastly more capable "studio" in the form of their mobile phone, demoscene devotees, chiptune aficionados, and retrogaming enthusiasts still clamor for authentic 8-bit sounds and the gear required to produce them.
As original hardware becomes more scarce, and prices necessarily skyrocket to as much as ten times their original MSRP, GitHub users @echolevel,@abrugsch and @mnstrmnch give salve to enthusiasts' wallets in the form of the Open Amiga Sampler — an open source, 8-bit, mono sampler "cartridge" which mates to the Amiga's 25-pin parallel port.
The OAS' creators go into great detail in the GitHub repo as to the precise workings of typical sampler carts of the period, but most were a simple PCB built around an 8-bit ADC and supporting logic, which makes them quite simple to reverse-engineer — and quite simple to reproduce! Despite the name, a sampler cart is not an edge-connecting "cartridge" like you may have blown on before booting up your favorite NES game, or jammed into the "ashtray" of a BBC Micro — rather, it is what might more typically be referred to as a "dongle" — taking advantage of the Amiga's bidirectional parallel port in order to send converted data from the ADC to Paula, the Amiga's famous sound (and I/O) chip.
One particularly interesting aspect of this project was the team's use of a Teensy 3.5 to simulate the Amiga parallel port, rather than risking damage to their beloved Amigas while exploring the realm of 80s sampler cart technology. The Amiga's Complex Interface Adapter (CIA) is both difficult and expensive to replace (averaging around $50 on eBay at present), and so much as accidentally knocking into a parallel port device can kill a CIA if you're lucky — and an entire Amiga if you're not! The Teensy's 5V-tolerant pins were a perfect match to the Amiga parallel port's +5V reference voltage, which powers the sampler's chips, and thus is also the range for returned data. The Teensy's onboard mSD card slot allowed the 8-bit sample data to be logged, then converted to .WAV files, providing insight as to whether sampled audio is sounding as it should.
The OAS has been tested and confirmed working with most popular sample trackers, such as ProTracker and OctaMED, and generally can be expected to be compatible with most software designed to work with the original TechnoSound Turbo and similar budget 8-bit carts.
Open Amiga Sampler PCBs have been made and tested — in fact Twitter user @ABrugsch has already created an SMD variant! Follow @echolevel on Twitter and the GitHub repo for more updates!