Ed Anderson and Hairball Audio, LLC commissioned Eisen Audio to re-engineer this classic discrete op amp, which was originally designed by the BBC for use in their 1970s Neve broadcast consoles. The transistors were substituted, the circuit reconfigured for operation from bipolar power supplies (instead of +24VDC), the broadcast filtering was removed for extended bandwidth useful in music recording, and of course the PCB layout was completely redone conforming to a standard 990/2520 footprint for use in DIY projects. The class A/B bias and heavy-duty heatsink means this amplifier can drive remarkably low impedance loads. Indeed, we generated a spec sheet via standard op amp testings which shows impressive numbers.
Manufactured by Eisen Audio in New York, and sold exclusively through Hairball Audio in Seattle.