TDK SD Super Dynamic Tape

TDK’s market reputation was made in the mid 1970s with their SD Series (Super Dynamic) tapes, a series of Low Noise / High Output tapes (type 3) that required a higher bias. This made these tapes sound brighter on older equipment, and when used with the older (and cheaper) machines at the time, users felt they sounded better due to their better frequency response, particularly at 3-3/4 ips. The curves published in the boxes of these tapes clearly showed this effect – did they know this would be a competitive advantage when compared with recordings made on tapes biased for the older machines? I remember my Father bringing one of these tapes home with our Sony TC-355, and he was amazed by the brighter – and louder sound. “The tape sounds better”, he said.  Later, machines with a tape selector allowed them to be used at the proper bias, where the full capabilities of the tape could be used. The SD tapes still hold their quality today and can be used today – and they still sound brighter on the older machines!

Note: The 1200 ft (360m) version on 7″ tape reels have reels with larger hubs using the same LP tape thickness of the 1800 ft (550m) version. To our knowledge, they never produced an SP or DP tape.

There were a number of packaging variations through the 1970s that included deep blue and gold packaging, plain white/black packaging, and a series with high quality white clam-shell plastic boxes made famous by BASF and AGFA.  All used the same windowless single thread gray plastic reel. There is no indication the tape formula changed during this time – all have a polished shiny black oxide surface.