Automated Processes, Incorporated, popularly known as API, has a rich history spanning over half a century. Since their first consoles were installed in 1967, API has developed new technologies, established important pro audio standards, and contributed to the production of many great records. Building on this legacy of audio excellence, they have recently introduced the ASM164, an analog summing mixer featuring 16 inputs with two stereo buses and a signal path based on the design of The Box console [Tape Op #101].
On first look, you will notice the rows of extruded aluminum knobs with colored centers set against the matte black panel of the ASM164. The level controls are detented attenuators that ensure matching, while the pan pots move smoothly with moderate resistance and have a solid center detent. The A and B bus switches are amber LED push-buttons, making it easy to identify their status, and the insert (INS) switches illuminate green when engaged. The icing on the cake is the pair of lighted analog VU meters, which adds to the visceral experience. It has the feel of a classic console in a small two rack space unit package.
What distinguishes the ASM164 is the 2520 op-amp and transformer output design that adds coloration and imparts the signature API sound, which is often described as warm and musical. These are fairly vague descriptions, and so to better understand these sonic characteristics, I conducted listening tests using a range of material, including ‘60s and ‘70s classics, indie, hip-hop, and electronic tracks. Throughout these sessions, it was discovered that certain elements, regardless of genre, are enhanced in specific ways.
The first test involved a classic rock session with stems for vocals, bass, drums, accompaniment, and backing vocals. To establish a baseline for comparison, I set up a mix in Apple Logic Pro [Tape Op #74] with panning and level adjustments. The tracks were then routed to the ASM164 as stereo pairs, and I engaged the 0 dB BYP button to set all inputs to unity gain. Immediately, the mix felt noticeably different. Everything seemed closer to the listening position, and vocals were especially more upfront. The bass track was panned off-center, and its position was distinguishable in the DAW mix. Through the API, the bass felt larger and occupied a bit more of the center. Drums exhibited a richer midrange presence, as did guitars, which also projected forward in the mix. For comparison, I ran the same session through a different summing mixer known for transparency. This mix had more spatial detail but lacked the pronouncement of the ASM164 mix.
To hear how the ASM164 sounds on a modern track, I set up a hip-hop session for testing. The vocal stems, heavily processed with Antares Auto-Tune [Tape Op #126] and compression, still popped up front and revealed more midrange detail. Additionally, transients of the programmed drum parts also exhibited a bit more crispness. Additionally, this track provided an opportunity to push things a bit and see how driving the summing bus with heavy Roland TR-808 bass drums would sound. The VU meters started pegging pretty severely, so I switched on the 10 dB meter attenuation located on the back of the unit. As I pushed the output level up to +6 dB, the 808 started to saturate with some nice, rounded harmonics, giving the drum samples a satisfying gritty vibe with musical character.
Throughout these sessions, the results were a consistent warmth to the midrange, and the low mids occupied a larger region in the stereo field. Upper mids were pushed closer to the listening position, and the center of the stereo image became more dominant. These qualities contributed to the cohesion of the mixes and lend to the description of being “musical.” I printed each of these sessions to compare with the DAW bounces on other systems. The warmth and presence of the API sound, whether through earbuds or a car stereo, always translated nicely outside of the studio environment.