The 660/670 limiter was designed by Rein Narma, who built the first 10 mono units by himself, the first one was made for Rudy Van Gelder a recording engineer specializing in jazz, Rein later built a recording console for him. The second 660 was sold to Olmstead Recording in New York and then the third to Mary Ford and husband Les Paul. Rein worked at Gotham Recording and then formed Gotham Audio Development Corp with others. He built new amplifiers for the Ampex 300 for a new product range for Gotham Audio. It was at that time Les Paul heard of Rein.