The Gates SA-39B limiting amplifier combines excellent performance with a focus on easy serviceability, continuing the legacy of earlier Gates limiters known for their outstanding quality.
This advanced limiter circuit in the Gates SA-39B was developed in collaboration with engineers from the British Broadcasting Company. Over time, the design has been refined, making this model a benchmark for smooth, rapid limiting and minimal distortion, even at extreme levels of compression.
The amplifier offers near-instantaneous attack times and six selectable release settings, allowing engineers to customise operation to their needs. It employs full-wave rectification of the output voltage, with the resulting negative current applied to the second control grid of the push-pull input stage.
As the output voltage rises on the Gates SA-39B, the grid becomes more negative, reducing amplifier gain. Despite its fast action, the unit avoids introducing distortion, even at compression levels up to 20 dB.
The circuit includes three push-pull stages with independent input and output level controls. The electronically regulated power supply features 6X5, 6SJ7, and 6L6G tubes with a 5V4G cathode-type rectifier, ensuring accurate limiter calibration across a wide range of line voltages. A 4-inch wide-scale meter provides precise compression level readings.
Designed with servicing in mind, the Gates SA-39B’s front panel can hinge down to reveal all under-chassis components. Cleaning the under-chassis is straightforward, using a bellows or suction cleaner, ensuring long-term, trouble-free operation.
