S500 II

About the S500 II

The Threshold S-500 MK II is an improved version of the original S-500 power amplifier, designed by Nelson Pass. It features the famous STASIS circuit topology and an optical bias system that enhances performance and reduces warm-up time. This amplifier delivers 250 watts per channel into 8 ohms with 0.1% total harmonic distortion and a frequency response from 7 Hz to 100 kHz. It can provide up to 100 amps peak current per channel, allowing it to drive difficult loudspeaker loads with ease. The amplifier uses 20 output transistors per channel and a powerful 1000W toroidal power supply with 120,000 microfarads of capacitance. It has balanced (XLR) and unbalanced (RCA) inputs and is capable of running a higher proportion of its power in pure Class A mode compared to earlier models. The S-500 MK II is known for its exceptional bass control, smooth midrange, and extended treble, making it a highly regarded amplifier for demanding audiophile applications. It weighs approximately 36 kg and measures 48.5 x 43.5 x 22.5 cm. This model is no longer in production but remains sought after in the used market.