Discrete Op Amps
A discrete op-amp is made from individual (discrete) transistors, diodes, resistors, capacitors, and, occasionally, inductors. These components are brought together on a circuit board or substrate to create the final circuit. Each diverse component is fabricated on a manufacturing line that is fully optimized for that specific part. Therefore, each component is the very best it can be. Low-noise input transistors are fully optimized for their unique requirements. High-power output transistors are fully optimized for their unique and very different requirements. Precision resistors come from manufacturing lines that are dedicated to making precision resistors. Capacitors come from optimized capacitor lines. Only after these fully optimized components are fabricated are they brought together ona circuit board or substrate. - J Hardy
This board has been designed by Gary Barnett of Barnett Industries. Gary has built upon the reverse engineering work of Peter Lazaro, better know as "Peter Purpose". This DOA is a nine transistor amplifier modeled after the legendary, mid '70's, Studio Systems/Huntington era 2520.
The Hairball Audio JE-990
Built to the specifications of Deane Jensen’s now famous JE-990 paper published in the February 1980 AES journal. The Hairball Audio version of the JE-990 utilizes a bottom layer mounted SSM2212 Analog Devices dual matched transistor
The John Hardy 990C+
The original 990 is by Deane Jensen of Jensen Transformers. Deane was awarded U.S. patent for aspects of this design. Every aspect of the design and performance of the 990 was optimised through extensive computer aided design and analysis.
Each component of this discrete op-amp was carefully chosen for its specific task, providing superior performance compared to monolithic opamps and other discrete op-amps.
The Avedis 1122
The 1122 is a high performance direct coupled operational amplifier designed specifically for professional audio amplifier applications, designed by Avedis Kifedjian and used by Brent Averil in their first 312A mic pres