The ACS1 contains six amplifier models based on fan-favorite amps, each with its place in music history, and twelve cab IRs (Impulse Responses) designed by world-class designers to give you the best tonal representation possible. The stock IRs for the Fullerton, London, and Dartford amp models were custom-engineered by David Hislop and Kenyon Reed at Tone Factor, while the stock IRs for the Red, Citrus, and Tread amp models were designed by Justin York at York Audio.