The Collins 26U-1 Limiting Amplifier is engineered to deliver maximum modulation with minimal distortion, ensuring comprehensive tonal range broadcasting without any thump.
This amplifier effectively limits loud audio peaks to avoid overmodulation, distortion, and interference with adjacent channels, while allowing softer audio to be broadcast with clarity.
The limiting function increases the station’s signal range and boosts transmitter efficiency by enabling a higher average modulation level.
When paired with recording equipment or public address systems, the Collins 26U-1 prevents overloading and supports higher average audio levels, enhancing the signal-to-noise ratio.
Its self-balancing circuit removes the need for careful tube selection or delicate adjustments commonly required with peak limiters. The Collins 26U-1 Limiting Amplifier achieves compression exceeding 30 dB.
It features conventional circuitry, negative feedback, full-wave rectification for control voltage, and silicon rectifiers within the power supply.
The VU meter on the Collins 26U-1, equipped with an illuminated scale, measures in both VU and dB compression up to 5 dB.
An attenuator and rotary switch on the VU meter allow for precise measurement of external gain reduction, compression, and input/output audio levels. This external metering setup can measure audio on other program lines, negating the need for an additional VU meter panel.
The power supply, built with silicon diodes and long-life electrolytic capacitors, is efficient, low heat, and requires minimal maintenance. A voltage regulator stabilises reference voltages, and the input, output, and VU meter levels are controlled using Daven step-type adjustments.
The Collins 26U-1 includes a push-pull variable gain input stage, push-pull interstage voltage amplifier, and a push-pull output stage. A bias rectifier derives DC bias from the output signal to control input stage gain. The unit also comes with a built-in power supply for plate and filament voltages.
It is designed for rack mounting, incorporating a minimal number of controls and tubes. The front panel is hinged for easy access to internal components and wiring.
The Collins 26U-1’s front panel is coated in blue-grey enamel, while the chassis is cadmium-plated and chromate-dipped for durability.
