The Langevin PROGAR 119-A amplifier is a combination of a fast-acting peak limiter and an automatic gain control amplifier with adjustable time constants. It features a semi-regulated power supply that ensures consistent performance.
The Langevin PROGAR 119-A provides approximately 53 dB of gain, requiring a signal input of -31 VU and outputting a level of +12 VU. The automatic gain control section consists of the first push-pull stage of the main amplifier and associated circuits, including a separate two-stage push-pull amplifier, diode rectifier, memory circuit, and conducting diode. This setup allows the amplifier to amplify and rectify output voltage and apply a bias for control.
The peak limiter section of the Langevin PROGAR 119-A uses the last three push-pull stages and a biased diode rectifier, rectifying and limiting output voltage when it exceeds a set threshold. The amplifier’s power supply is semi-regulated and provides plate current, filament power, and pilot lamp voltage. It is recommended to connect it to the same AC power source as the transmitter modulator for compensating for power variations.
For input level adjustments, the primary input level required for proper operation of the Langevin PROGAR 119-A is approximately -31 VU. The amplifier includes an adjustable attenuator on the front panel with a range of 15 dB in 0.5 dB steps and a semi-fixed attenuator under a dust cover at the rear of the chassis, adjustable from 1 to 40 dB in 1 dB steps. The semi-fixed attenuator must be connected during installation based on the anticipated line level.
For output level adjustments, the output level at the threshold of limiting is approximately +12 VU. A variable output attenuator is controlled from the front panel and provides a range of 4.5 dB in 0.1 dB steps without insertion loss when set to zero. The semi-fixed attenuator at the rear allows for up to 40 dB attenuation in 1 dB steps and must be connected during installation according to the desired output level. At least 6 dB attenuation is recommended for isolation purposes.
Developed by engineer Towne over a decade, the Langevin PROGAR 119-A Peak Limiter was marketed by Langevin as a solution for automatic audio level control in broadcasting. However, its slower recovery time made it less suitable for dynamic content like early rock and roll radio, leading to its limited adoption.
Today, the Langevin PROGAR 119-A Peak Limiter is considered a collector’s item due to its scarcity and historical significance. While some appreciate its unique sonic character, others find its performance less practical compared to modern compressors. Its large size and the need for a separate power supply can also be seen as drawbacks.
The Langevin PROGAR 119-A Peak Limiter is a notable piece of audio engineering history, valued by collectors and vintage audio enthusiasts for its unique design and role in the evolution of early audio processing technology.
