The Ampex 631 is the SP (standard play) version of the latest and most improved variation of their classic brown oxide formulation (600 Series) produced from the early 1950s with the company’s Ferrosheen process, developed at the time to give the tape a smoother finish and better frequency response than competing tapes. The 631 was produced well into the Quantegy days, misleadingly sold as an inexpensive “voice grade” tape towards the end of its run. The reality is that the 631 is one of the most reliable and longest lasting tape formations ever produced. It is classified as a “standard” tape (Type 1) and should be biased accordingly.  It was never sold as a “Low Noise” formulation.  There is attached documentation from the late 1960s comparing its performance to the 500 series tapes.  The quality was very high for its time, with lower than average oxide shed. This tape was produced throughout the 1960s and early 1970s.  Notes:

• This is a formula that has withstood the test of time. It is amazing to consider that you can make a high quality recordings on a 60 year old tape, but this is indeed possible.
• Tapes of this vintage have a tendency to shed oxide more than modern tapes, although we have found that tapes made by Ampex from this vintage are better than most, especially later batches that presumably adopted the modern production methods of the newer tapes.  Keep in mind that oxide shed is not a sign that this tape is degrading, it should be considered normal.
• There are some batches of this tape sold as high end consumer tape, with plastic boxes and attached leader tapes. Most 631 did not come that way – most of it was sold in bulk for other purposes.
• This tape formulation was often used for commercial tape duplication, particularly since Ampex ran their own commercial tape duplicating business. They also had large government contracts for this type, which you see occasionally for sale with the single window reel.
• Available Refurbished: Yes, you can buy refurbished reels of 631 in our store and they are highly recommended. They were shipped in a variety of packaging and reel designs.