Objectives in High Fidelity Amplifier Design 1945 Written when Dick Burwen was a freshman at Harvard, this article showed the need for equalization to compensate poor frequency response in speakers and program sources. The article was sold to a now extinct magazine, but never published.
Krohn-Hite Ultra-Low Distortion Power Amplifier, Instructions for Model UF-101, 1954 Krohn-Hite UF-101.pdf. 50 watts at 0.005% distortion from 4 - 6550 tubes, produced for 20 years as a laboratory instrument, designed by Dick
Burwen Laboratories Noise Eliminator Model 2000 - 1970s This was Dick's toughest engineering challenge - a 3:1 companding noise reduction system that added 50 dB dynamic range to an analog tape recorder. It did not quite sell to A & M Records who loved the performance, but decided not to try to lead the recording industry to a new recording standard instead of Dolby. Dick made many live classical concert and studio recordings via the Noise Eliminator before digital tape became available. Unfortunately the oxide on analog tapes of that era deteriorated. A few years ago Dick threw out a roomful of these wide dynamic range tapes because he did not want to spend the rest of his life baking tapes to restore them.
Burwen Laboratories Modules MP202, UM201, and VU306 - 1970s These epoxy potted modules were designed for use in the Burwen Laboratories Model 1000 Dynamic noise filter and the Model 2000 Noise Eliminator. Some were incorporated in Mark Levinson's famous LNP-2 Preamplifier. Dick's 20,000-watt sound system still uses more than 250 of these modules.
The MP202 is a microphone preamplifier; UM201 is a Universal Mixing Amplifier; and VU306 is a Peak VU meter circuit. Dick was able to greatly improve the high frequency performance of their Harris HA-911 op amps via a more complex stabilization network, and they were selected for low noise and DC offset. Product lliterature - Burwen Laboratories MP202 UM201 and VU306.pdf
Burwen Laboratories Low Noise Stereo Preamplifier Model SP5200 Operating and Service Manual - Preamplifier Burwen Laboratories Model 5200.pdf A flat response stereo preamplifier that accepts phono and numerous sources. Only about 10 manufactured in 1972. It may be better than today's preamplifiers.
Letter on Transient Noise Eliminator, 1978. Dick designed this device to remove ticks and pops from phonograph records. It was manufactured by KLH Burwen Research.
Cello Audio Palette - 1984 Mark Levinson's Cello Ltd. product, the Audio Palette tone control system was a remarkable success and manufactured for many years. Dick submitted this schematic, description, and tentative specifications and features of a Program Equalizer to Cello Ltd. on March 3, 1984 and it became the basis of the Cello Audio Palette. This design used a large number of integrated circuit op amps. Cello wanted to achieve the best possible performance and make it bullet-proof against possible criticism of its op amps. They replaced the important signal processing op amps with their own proprietary discrete component op amps, greatly increasing the manufacturing cost. The final production circuit, aside from the op amp design, was simplified somewhat in order to use fewer op amps.