HP 200A

HP 200A. The HP 200A was the first product manufactured by the Hewlett-Packard company, founded by Bill Hewlett and David Packard. This precision audio oscillator was notable for its innovative use of a Wien bridge circuit and a pioneering incandescent light bulb as a stabilizing element, providing exceptional frequency stability and low distortion. Its commercial success, particularly a large order from Walt Disney Productions for the Fantasound system used in the film Fantasia, provided the critical capital that launched Hewlett-Packard as a major force in the electronics industry.

History and development

The development of the HP 200A originated in the now-legendary Stanford University garage in Palo Alto, California, where Bill Hewlett worked on his master's thesis under the supervision of Professor Frederick Terman. Frederick Terman, often called the "father of Silicon Valley," encouraged his students to start their own companies. Bill Hewlett's design solved a key problem in Wien bridge oscillators—amplitude stability—by incorporating a small incandescent light bulb in the feedback loop, whose resistance varied with temperature to automatically regulate gain. This simple yet brilliant solution was patented by Bill Hewlett, and with an initial investment of $538 from David Packard, the partners began production. Their first major client was Walt Disney Productions, which purchased eight units for testing the innovative Fantasound multi-channel sound system for the animated feature Fantasia.

Technical specifications

The HP 200A operated over a frequency range of 35 Hz to 35 kHz, divided into four ranges selected by a rotary switch. Its core innovation was the Wien bridge network, which determined frequency, coupled with a two-stage vacuum tube amplifier using a 6SJ7 pentode and a 6F6 beam power tube. The stabilizing element was a General Electric #181 incandescent light bulb. The device offered a low-distortion sine wave output, with harmonic distortion typically below 1%. Output level was adjustable via a calibrated attenuator, and the unit was powered by standard AC line voltage. Its performance specifications far exceeded those of existing audio oscillators like those from General Radio, setting a new standard for the electronics instrumentation field.

Impact and legacy

The success of the HP 200A had a profound impact, solidifying the reputation of Hewlett-Packard for quality and innovation and providing the financial foundation for the company's future growth into a global technology leader. It is widely regarded as the foundational product of Silicon Valley, symbolizing the region's shift from agriculture to high-tech industry. The instrument's design philosophy—reliable, precise, and useful—established the core values of the Hewlett-Packard corporate culture. Furthermore, the story of its development in a Palo Alto, California garage has become a central myth in the lore of American entrepreneurship, inspiring countless other engineers and entrepreneurs. The original HP 200A is now a prized artifact, with examples housed in institutions like the Smithsonian Institution and the Computer History Museum.

Design and features

The design of the HP 200A was defined by its robust, functional bakelite case and clear, user-friendly front panel layout. The most significant feature was the innovative application of the Wien bridge circuit, which provided excellent frequency selection, combined with the novel use of the incandescent light bulb as a non-linear resistor for automatic gain control. This bulb, acting as a thermistor, provided inherent amplitude stability without manual adjustment. The chassis was constructed from heavy-gauge steel, and the circuit utilized high-quality components to ensure reliability. This focus on fundamental sound engineering, rather than cosmetic appeal, set a design precedent for subsequent Hewlett-Packard test equipment and influenced the entire electronics instrumentation industry.

Production and variants

Initial production of the HP 200A was extremely limited, handled entirely by Bill Hewlett and David Packard themselves in their garage workshop. Following the pivotal order from Walt Disney Productions, which was for a modified version known as the HP 200B, production scaled up. The HP 200B variant featured a different output connector to meet the specific needs of the Fantasound system engineers. This model was succeeded by the improved HP 200D, which offered extended frequency range and other refinements. These early models established a product lineage that evolved into the famous HP 200 series of audio oscillators, which remained in production for decades and were used worldwide in laboratories, broadcasting stations, and manufacturing facilities for audio frequency testing and calibration.

Category:Electronic test equipment Category:Hewlett-Packard Category:Audio test equipment Category:1939 introductions