6Advanced Bionics: 16 Current Sources and Current Steering

TSixteen current sources

Every modern AB implant (HiRes 90K, 90K Advantage, HiRes Ultra, Ultra 3D) carries exactly 16 platinum contacts, each wired to its own independently programmable current source with its own output capacitor. This 16-current-source design is the hardware basis for simultaneous paired stimulation and current steering, distinguishing AB from devices that multiplex fewer sources.[2020]

CHow current steering works

Current steering delivers charge-balanced, in-phase pulses to two neighbouring contacts at once and varies the current ratio, steering the field peak to a site between them and eliciting an intermediate pitch. The clinical implementation, HiRes Fidelity 120, can create up to 120 spectral bands across the 16 contacts (15 inter-electrode gaps).[2012]

TDo virtual channels help?

Discriminable virtual-channel pitches vary widely: Koch et al. found a mean of about 93 (range 8 to 466), but some patients could not discriminate even adjacent physical contacts. Controlled trials have generally shown small or no consistent speech-in-quiet benefit of HiRes 120 over standard HiRes, with a downside of degraded temporal fine timing from the longer (~15 ms) FFT window — despite patient-reported music gains.[2007]

CHiRes and Optima

HiRes is a high-rate CIS-family strategy using up to 16 channels; non-simultaneous stimulation across all 16 can reach ~2900 pps/electrode for an aggregate of ~46,400 pps. HiRes Optima lowers compliance voltage from 8 V to 4 V and stimulates only via virtual electrodes, improving average battery life by ~53% with comparable speech outcomes (cross-ref Ch.8).[2014]

TLower-profile and 3D cases

HiRes Ultra uses a lower-profile 4.5 mm titanium case (versus ~5.5 mm / ~12 g for HiRes 90K), attractive for infants and young children. The Ultra 3D adds a magnet that freely reorients in three dimensions to align with the external MRI field, allowing 3.0 T MRI with the magnet in place and reduced pain, displacement risk and bandaging (cross-ref Module 15).

CResearch platforms

AB also provides research/fitting platforms — the Bionic Ear Programming System (BEPS+) and HRStream/PulseWave — that expose HiRes 90K functionality for investigational sound-coding work, interfacing via the CPI-2/CPI-3 boxes.