This is the highly regarded LA500A Compressor. It's a fantastic optical compressor based on the LA3A, but with more features including switchable side chain high pass filters, three selectable compression ratios, and also the new 'Slow Attack Mode' which is allows you to pull the threshold knob to engage a slower attack time (very nice on bass).
These are extremely versatile compressors, and they work great on almost any source.... vocals, guitars, bass, etc. It's a very smooth and warm sounding compressor that adds some definite heft to the low end. But given the variety of settings, it can also be very transparent, and not overly colored, even at high levels of gain reduction.
• Large 34mm white LED backlight GR/VU meter. • Hard relay bypass when comp power off or switched to LA OFF. • Meter switchable Gain Reduction / LA OFF (meter led off) / VU by toggle switch • Electronic balanced input to handle extreme input levels without distortion. • Large 32mm chicken head input level control for easy setting of compression level. • Large 32mm Makeup level pot with 0 to 20dB of gain. • Ratio switchable 3:1, 5:1 & 10:1 by toggle switch • SideChain High Pass Filter switchable FLAT, 100Hz, 200Hz. • Huge output transformer (same size as Neve LO1166). • Internal jumper for output ground lift. • Double sided Gold plated rear edge connector. • 3mm black anodised laser cut, vertical finished with white lasered on text for long lasting zero wear finish. • Mix buss output on pin 11 for Radial Workhorse rack