Dick Burwen

At the early age of eight Dick knew he wanted to design electronic equipment. Inspired by his father Henry Burwen, who once worked in a radio
store, he built several crystal radios, graduating to single tube, two tube, and three tube circuits. At 14 he acquired professional first class
radiotelephone and second class radiotelegraph licenses and had built his amateur radio station, W1NMG. During his high school years in Melrose,
Massachusetts Dick and his dad serviced radios in their basement. Dick did the troubleshooting and his dad refinished the wooden cabinets. World
War II was under way and Dick worked for a year after school at National Company Inc. aligning and troubleshooting the Navy version of the HRO
short wave receiver.

Dick got hands-on experience at the Navy Radio Technician training schools and theoretical training at Harvard where he earned Bachelor’s and
Master’s degrees. At Bell Laboratories during the summer of 1949 between semesters, he designed a tracking band-pass filter. His first job after
finishing graduate school was at Spencer-Kennedy Laboratories, Inc. where he designed all the RF distribution networks, and planned and
supervised the initial installation of the second cable TV system built.

At Krohn-Hite Corp. Dick designed the laboratory UF101 Ultra-Low distortion Power Amplifier. Using type 6550 output tubes in a multiple-loop,
high-feedback system, this amplifier, rated at 0.005% distortion was manufactured in small quantity for 20 years. From 1955 to 1961 Dick designed
hi-fi equipment at National Company, Inc., circuits for military equipment at Norden-Ketay Corp., sensitive DC measuring instruments and a 1 kW
transistor power for Navy sonar research at Honeywell Corp., Boston Division. During weekends and evenings he designed circuits as a consultant
to other companies.

In September 1961 Dick quit his job at Honeywell to become a full-time circuit design consultant, working at his well equipped home laboratory for
more than 60 different companies during the next 42 years. He has authored more than 30 technical articles and received 10 patents; others are
pending. Among the circuits Dick has designed are numerous medical instruments, industrial controls, laboratory test instruments, power supplies,
aircraft instruments, automobile ignition, detectors, high resolution video displays, and analog IC’s.

Dick got into a lot of really interesting projects. Among the more challenging projects were ultra-low drift chopper-stabilized DC data amplifiers, IC
multipliers and function generators, magnetometers, and low-noise switching power amplifiers. He designed circuitry of the first transistorized
blood cell counter, a seizure detector for epilepsy, photoelectric relays, high resolution CRT displays, early projection color TV, a military satellite
spin detector, and magnetometers for ground use and aircraft. His spacecraft magnetometer circuits successfully measured the magnetic field of
the moon from orbit.

When the government shut down ham radio for security reasons during World War II Dick became interested in hi-fi sound reproduction. In
college and graduate school at Harvard, Dick’s advisor was F. V. Hunt, inventor of the first low-pressure phono pickup – it tracked 16-inch
transcription discs at only 5 grams instead of ounces. Dick was inspired to spend every afternoon in the Physics Library reading every article in
every publication that had anything to do with acoustics and music recording and reproduction. When Dick asked to take courses outside the
normal curriculum, Dr. Hunt asked: “Do you want to become a scientist or an audio nut?’ Dick’s answer: “Both”.

Dick’s passion for audio has been steady for more than 60 years. Much of his life’s work in both audio and consulting for various companies has
been in multiple-loop high feedback systems. His developments in audio led to advances in his consulting projects and vice versa. The op amps
Dick designed for his own hi-fi system started semiconductor manufacturer, Analog Devices, Inc over 40 years ago. He worked for the company for
a number of years as a consultant, designing many analog modules, and later, integrated circuits.

For the past 20 years his consulting work has been almost entirely for Copley Controls, Corp., of which Dick is a founder. The company started
producing Burwen designed switching servo amplifiers. A customer in the MRI business found that seven of the book size Model 220 amplifiers in
parallel on each of three axis eliminated two racks full of linear amplifiers, allowing an MRI system to fit into a trailer. Since then Copley Controls
has become dominant in gradient amplifiers. About 25% of the worlds hospital MRI systems use Dicks circuits.

One of Dicks clients in 1961 was Lafayette Radio, a New York parts distributor. Technicians in the store basement manufactured a 160 Watt
Transistor Stereo Power Amplifier of Dick’s design. The output stage used series connected germanium power transistors. In the early 1970’s a
new company, Burwen Laboratories, Inc developed the Model 2000 Noise Eliminator, a 3:1 companding noise reduction system that extended the
dynamic range of an analog tape recorder to 110 dB. It did not quite sell to A&M records who feared setting a new industry standard different from
Dolby. Burwen Laboratories did sell about 150 of its $3500 Model 1000 Dynamic Noise Filters. These one-way noise reduction systems for existing
records and tapes were used by recording studios and FM stations for many years.

Dick built his first major hi-fi system when he was in high school and a freshman at Harvard. In contrast to his present 20,000 watt system, it used a
3-watt amplifier. In common with the present system, it used feedback to boost extreme high and low frequencies to compensate for speaker loss
and it had colored lights – Christmas tree lamps. You can read about Dick’s present system and Audio Splendor software at http://www.
burwenaudio.com In the years between these two hi-fi systems Dick built ever more powerful and flexible systems. Much of the improvement
resulted from tone control development that compensated the speakers and program sources.

As a consultant Dick helped Mark Levinson with the first products of Mark Levinson Audio Systems and Cello LTD’s Audio Palette. Millions of
National Semiconductor DNR chips licensed under Dick’s patents appeared in car stereos and other products. Now mostly retired from consulting,
he is busier than ever with new computer audio software. He has been married to his wife Barbara for 50 years.

AUDIO
Tone Control Software
Reverberation Software
Audio Pallete
Noise Eliminator
Dynamic Noise Filter
Transient Noise Eliminator
Rotating Speaker Simulator
200 Watt Ultra Low Distortion Power Amplifier
8 Kilowatt Color Organ
Minus Noise Mixer
Tape Recorders
Volume Expander Compressors
Electronic Reverberation
Portable Transistor Music
System
Peak VU Meter
Tone Control Systems
Binaural Headphone Driver
Microphone Mixer
Musical Instrument Enhancement
Speaker Equalizer
Mixer Bass Blender
Phono Preamplifier
50 Watt Integrated Stereo
Graphic Equalizer
High Speed Limiter
Pitch Shifter
120 DB Dynamic Range Equalizer
4 Channel Power Amplifier
System
Antenna Amplifier
Op Amp Stereo
Overload Protection
Half Octave Filters
Electronic Crossovers
Low Noise Microphone
20 KW Speaker System
Intercom Systems
Stylus Force Gage
Low Noise Preamplifiers
Hum Filter
Wide Range Remote Equalizer

AUTOMOTIVE
Ignition Systems

SEABORNE
1kW Sonar Power Amplifier

DETECTION
Magnetic Gradiometer Electronics
Chopped Light Photoelectric Relay
Magnetometer Electronics
Radar IF Strip
Metal Detector
Proximity Switches
Photolectric Controls
Burglar and Fire Alarm

GROUND SUPPORT
Pressure Transducers
Strain Gage Amplifiers
Intercom Amplifier

POWER SUPPLIES
HIgh Performance Regulators
Current Sources
50 KV Supply
Frequency Changers
Overload Protection
Line Voltage Regulator
SCR Converters
Phase Controlled Regulators
Precision AC Sources
Subminiature Power Converters
Shunt Regulator Modules
Neon Sign RF Supply
Switching Regulators
Subminiature Dual Supply
Battery Float System
Hiqh Isolation Converters
Low Noise Medical Supplies

VIDEO
Projection Color Receiver
Image Storage Systems
Community TV Amplifiers
Facsimile Video Processor
Precision Deflection Amplifiers
Linearity Correctors
Video Amplifiers
IF Strips
Cable TV Distribution Networks
Barre, Vermont Cable TV System
Character Deflection Amplifier
Crystal Oscillators
Chroma Demodulator
Precision Pulse Delay
Blanking
Grid Bias Controllers
Precision Sweep Generators
Focus Regulators
Digital Programming
Dynamic Focus

MEDICAL
MRI Gradient Power Amplifiers
Ultrasound Monitor
Blood Pressure Module
Blood Cell Counting and Sizinq
Cardiotachometers
EEG Preamplifiers
EKG Preamplifiers
Seizure Detector
Response Analyzer
Linear Ohmmeter
Amplifier Noise Filter
Continuous Performance Tester
Channel Selector
Baby Monitor
Blood Oxygen Monitor
PH Preamplifier
Temperature Measurement System
Automatic Gain Control
Temperature Controller
Battery Charging System
Carbon Dioxide Monitor

SPACE VEHICLE
Analog to Digital Converter
Magnetometer Electronics including:
Phase Locked Loop
Spin Demodulator
Carrier Amplifier
DC Signal Processing
Milliwatt Power Converter

CABLE TV
System Distribution Networks
Giant Horn Antenna
Barre, Vermont System, 1952
Other Towns

LABORATORY
Gas Pollution Monitors
Magnet Controller
Audio Time Correlator
DC Data Amplifiers
Pen Motor Drive Amplifier
Servo Recorder
Beam Current Controller
Accelerometer Amplifier
Square Wave Generator
Humidity Sensor
Microwatt Meter
Semiconductor Testers
Low Noise Preamplifiers
Electronic Thermometer
Multiplier Tester
Streaming Current Detector
Film Motion Controller

INTEGRATED CIRCUITS
Multipliers
FET Operational Amplifier
Low Drift Amplifier
CRT Distortion Corrector
Proximity Switch

FUNCTION MODULES
Precision Rectifiers
Wide Band Gain Controller
Power Supply Regulators
DC Operational Amplif iers
Chopper Stabilized Amplifiers
Sample Hold
Analog to Digital Converter
Binary to BCD
Active Filters
Comparators
Voltage Variable Filters
PWM Multipliers
Data Amplifiers
Peak Followers
Multiplexers
Low Noise Amplifiers
Oscillators
Automatic Level Control
Active Transformer
AC Operational Amplifiers
Servo Amplifiers
Digital Tape Head Electronics

AIRBORNE
Temperature Gage
Low Altitude Warning System
Scan Converter
Magnetometer
Aileron Control
Synchro Amplifier
Temperature Controller
Lamp Flasher
Noise Rejection Amplifier
Servo Amplifier

INDUSTRIAL CONTROL
Switching Servo Amplifiers
DSP Servo Amplifier
AccuData II Chopper
Stabilized DC Amplifier
Laser Trimmer Control
DC Operational Amplifiers
Particle Size Analyzer
100 Watt Valve Driver
Digital Analog Position
Programmer
Photoelectric Relays
Power Operational Amplifiers
MultiplIers
Pulse Width Modulators
Lamp Dimmers
Chopper Amplifiers
Peak Voltmeter
Logarithmic Amplifier
Liquid Mixture Control System
Braking Energy Absorbers
AC Current Limiter
Nanovolt DC Amplifiers
Motor Speed Control
Temperature Measurement
Integrators
Proximity Sensors
Voltage Controlled Oscillators
Phase Shifter
Stable Oscillators
Precision Charge Dispenser
Phase Sensitive Demodulators
AC DC Converter
40 Watt Torque Motor Driver
Die Bondier

The power amplifier delivered 3 watts from a single 6L6G pentode, with feedback that equalized the speakers at extreme high and low frequencies
as much as 30 dB. Bass and treble controls provided flexibility. The speaker system consisted of a Jensen15 inch coaxial and two 5-inch tweeters.
A labyrinth inside the cabinet extended the low frequency response. It had colored lights and the sound was loud, brilliant, and deep, without boom.
.
A 25 pound steel plate substituted for the original 78 rpm phono platter, and the Audax pickup used the first diamond stylus. Before that, sapphire
styli lasted only 25 plays.

When Dick was a freshman at Harvard he sold a long technical srticle on this system to Radio News magazine called "Objectives in High Fidelity
Amplifier Design". It advocated a large rise in frequency response at 30 Hz and 15 kHz instead of flat rsponse. The article was never published.

After showing it to a few potential customers Dick realized that those who appreciated the sound didn't have enough money and those who had the
money didn't care. About the same time a call came from Spencer-Kennedy Laboratories, Inc. who needed an engineer. That was Dicks first
two-year job where he became a pioneer in cable TV.

Burwen Laboratories and later KLH Burwen Research produced his one-way consumer noise reduction system in the early 1970s. It reduced hiss
from tapes and records with little effect on the sound. It worked by cutting off high frequencies at 9 db/octave during quiet music when there is little
harmonic content, and gradually and automatically extending the bandwidth beyond 20 kHz when there is loud high frequency content.