The Ampex 351 / 551 /951 are DP (double play) tapes of the 300 / 500 / 900 Series, first introduced under the Irish brand as the 300 series.  These tapes are characteristically VERY thin. The brown oxide appearance is similar to most other Ampex Ferrosheen tapes made from the 1950s through the 1970s. The “51”  refers to “polyester, double play”.  In general, we recommend any of theses Ampex or Irish tape for Standard (type 1) applications made with their Ferrosheen process due to their longevity, low oxide shedding, and excellent frequency response for the time.  They were superior to the Scotch 200, as those did not have the smooth surface of the Ferrosheen tapes. Our tests showed that the performance of the 351, 551 and 951 were virtually indistinguishable and can be considered identical for today’s purposes. Notes:

• These formulas have 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. This is not a sign that this tape is degrading, it should be considered normal. Ampex tapes made with their Ferrosheen process seem to shed less today than their counterparts, and should be considered to be at the top of the quality chart for tapes made at the time.
• The general quality of these tapes increased over their production run as general improvements were made, particularly with oxide shedding and smoothness.
• Ampex tapes included the formula code on the tape hold down tab, supplied when new. Many users kept the tab or stuck it to the box, so this might help you identifying a formulation.
• Later versions of 351 were sold with black and silver boxes as “PRT 2400”, an acronym for “Polyester Recording Tape”.
• As with any thin tape, extra care must be taken when handling as it can easily stretch or crumble under stress.
• Like Scotch or Audiotape, Ampex used the same oxide coating of the SP and LP tapes together with the thin 0.5 mil backing, so performance should be identical to the thicker tapes.
• Available Refurbished: Yes, you can buy refurbished reels of 351, 5541 and 951 in our store when available. They are relative rare.