Project Lead Engineer. Responsible for all circuit design, system architecture, layout and coordination with mechanical, Product Development (PD) and New Product Introduction (NPI) teams to assure product meets performance, cost and scheduling targets. My specific role was to launch a refresh of existing models and design and incorporate the constant power version into the family using a common PCB.
Description:
This amplifier is a member of the XTRA Series line of half rack amplifiers. All the amplifiers in this series have professional grade THD+N and SNR figures, with unweighted noise floors typically exceeding 105dB. All models are Energy Star qualified and feature power factor correction. The amplifier stages utilize fixed frequency, naturally sampled modulators driving a Class AD output stage. This series includes low impedance, 70V and 100V models as well as a low impedance constant power model.
Innovations:
To allow bidirectional transfer of control and state information between the amplifier and power supply, circuitry was devised which piggybacks information on top of that already being transmitted across an existing primary-secondary isolation boundary. This eliminates the additional cost and real estate optocouplers or transformers would entail.
The constant power model delivers 100W into either 4Ω or 8Ω by using a unique fast feedback-based audio signal/power limiter. My goal was to protect the load while simultaneously duplicating the electrical and sonic signature of an amplifier running a lower voltage rail for low impedance operation. The issue to address was that while a fast attack limiter would remove steady state clipping, the initial impulse would pass though unimpeded, temporarily delivering twice rated power to the load. To solve this problem, a circuit was devised which engages an auxiliary feedback loop whose bandwidth extends across almost the entire audio band. This actively and immediately limits the signal, protecting the load while the long-term limiter comes into play. This behavior is analogous to how a voltage limited 100W at 4Ω amplifier would behave.
