Shamrock and Emerald were budget reel to reel tape brands manufactured by Irish / Ampex through the 1960s to 1980s. There was an additional Emerald white box tape out of England, but this is not covered here. They used the internal nomenclature of Ampex at the time – and like the Ampex tapes the tape hold-down tabs from Ampex always included the formulation code.

011: Standard Play Acetate

021: Long Play Acetate

031: Standard Play Mylar (Polyester) – Also sold as Concertape through Radio Shack

041: Long Play Mylar (Polyester) – Also sold as Concertape through Radio Shack

051: Double Play Mylar (Polyester)

According to experience, the quality of these tapes varied tremendously, depending on when and where you bought them. Mostly they were non-spec tapes based on regular Ampex formulations. Tests have shown that many formulations suffered from inconsistency, output variations, and dropouts. We do not recommend that these tapes be used for critical recordings. Some of the formulations were sold spliced from the factory – and here you can tell if the color of the tape is slightly different from the two batches spliced together. However, many have had good luck with their Shamrock tapes. We have identified 8 generations of this tape:

  1. Early generation acetate / mylar tapes are based on the standard (type 1) tapes sold by Ampex in the 1960s and early 1970s, without back coating. These are still playable and have no sticky shed. You can identify them through their oxide color (brown) and that they have no back coating. These are the most reliable Shamrock tapes, and we offer these as refurbished with their formula called out (Shamrock Type 1: Ampex Ferrosheen Brown Oxide). Some of the tapes perform similar to Ampex 651 or 671.
  2. Grey oxide tapes based on Low Noise formulations, also without sticky shed or back coating, in 031, 041 and 051 versions. There has been sightings of 034, 044 and 054 versions titled as low noise. Update 10/2023: early batches of this tape perform very well and we now recommend using it. They often have a gray reel that is partially shiny identifying them as older lots. Later lots have a thinner oxide coating and perform like type 7 tapes. These might not be sticky but their performance is poor.
  3. Grey oxide tapes without back coating WITH sticky shed, we did not play or test these tapes but discovered them during our processing.
  4. Grey oxide tapes with back coating, without sticky shed – these tapes have a slight brown tint and were also sold as Concertapes. The quality is OK on these. As of this writing, we are still evaluating whether these can be sold as refurbished. Update: some of these tapes are OK, others suffer from sticky shed, and some we found spliced.
  5. Brown oxide tapes with a graphite backing, tape otherwise used for 8-track cartridges, known as “cartridge tape”. They do not have sticky shed and can be played without problems. We also offer these as refurbished with their formula called out, as some people want the tape to load into their 8-tracks (Shamrock/Concertape Type 5: Ampex Graphite Backed Brown Oxide / Cartridge Tape). This tape was optimized for 3-3/4 ips tape speed as used in 8-track cartridges. A significant amount of these tapes were sold with a splice in the middle, that unfortunately by now has a failed adhesive, so watch out if you plan to use them again.
  6. Back coated master tapes with brown oxide in 031 and 041, especially popular in Europe as they were sold alongside BASF tapes in European department stores through the 1980s. These tapes have a light green or blue box, and suffer greatly from sticky shed just like the master tapes do. The blue or light green box might even state that the tape is back-coated. Unfortunately none of this tape is usable today without baking.
  7. Back coated instrumentation tape sold as 041. This has a shiny grey oxide, and the tape is thinner – you can identify this tape in that it looks like the reel is not filled with tape. This tape suffers from sticky shed. Also, it has a very low output and a strange bias characteristic that made it good for 3-3/4 ips and a noise reduction system at the time. This formulation was commonly found in mid-1980s Concertape. Unfortunately none of this tape is usable today without baking.
  8. Back coated grey oxide tape sold as 041 with a more favorable performance characteristic, but similar sticky shed properties. These tapes are identifiable in that they almost fill the real, unlike type 7. They also have a distinctive pungent smell. This formulation was also commonly found in mid-1980s Concertape. Unfortunately none of this tape is usable today without baking.

NOTE: Tapes that are factory spliced typically have their splices fail by now, so you want to repair the splice before you use the tape. You can tell that a tape is spliced because there is a slight color change when you see the two different batches of tape spliced together.

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