Dick's Tidbits
Ideas, thoughts, and comments on audio etc., updated occasionally

Unpublished Article On Upgrading My Computer in 1997 - Tragically hilarious.

Dick Burwen's Famous
Strawberry Lemonade Recipe - Served during Hi-Fi nights.
A product of 10 years of research.

Dick Burwen's new Quick Strawberry Lemonade Recipe, 2010
Save a half hour of lemon juicing.  Tastes about as good.

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 Model 1000 Dynamic Noise Filter - 1970s
A one-way noise reduction system for tape hiss and record rumble used by recording studios and radio stations.
Product literature -
Dynamic Noise Filter Model 1000 - March 1974.pdf
How it works - A Dynamic noise Filter for Mastering - Audio June 1972.pdf
How to operate and fix it - Dynamic Noise Filter 1000 Manual.pdf

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.

Product literature -  
Noise Eliminator Model 2000 - August 1972.pdf
Technical description - 110 dB Dynamic Range for Tape - Audio June 1971
AES show report - Doctoring the Signal - E. T. Canby - Audio February 1972

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

Letter from Eventide to Dick in 1985 regarding the force of his hi-fi system.

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.

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.

Here are links to other information on the Audio Palette.    
Catalog -
Owner's Manual -

These files are in Adobe .pdf format.  If you do not have the Adobe Reader installed, you can download it for free from Adobe.