Occasionally we receive quarter-inch tapes that will be on small 3-inch spools. The result will have speed variation when reproduced on our capstan drive machines. They start very fast then gradually slow down throughout the recording to normal speed.
These reels usually have been recorded on rim drive machines. These open-reel tape recorders didn’t use a capstan and pinch roller to save space and more often cost as there is no capstan; as the supply reel gets smaller, the tape recording speed increases.
It’s not feasible or desirable for an audio restoration company to own unlimited machines of all types due to the time to service and repair them, find parts and storage space needed. Therefore, we use a small range of carefully picked high-quality tape machines that can replay most tapes, speeds, and track formats with care. This is the problem with rim drive recordings, and a digital solution is available at Creative Audio Works. This same process can correct speed variations caused by recorders that used batteries that run low during the recording.