Teac MTT-5561
A chromium-dioxide reference cassette, part number 4900041900 - the tape a technician loaded when a Teac deck needed to be set up for chrome.
Overview
The MTT-5561 is a blank test tape, not a machine. Teac sold it under part number 4900041900 as a CrO₂ reference cassette. It turns up in the service documentation for the company's cassette decks as the tape named whenever bias and record parameters had to be set for chromium-dioxide stock. That is the whole job. The technician reaches for it, and the deck's own alignment procedure assumes it is already on the hubs.
The MTT-5561 is one tape in a system of tapes. Teac aligned its cassette decks against a small family of reference cassettes, each covering a different formulation. The MTT-5511 handled NORMAL tape. The MTT-5561 handled CrO₂. The MTT-5571 handled METAL. The service manual says which one to load for which adjustment. Bias oscillator setup on the W-520R, for instance, calls for the MTT-5511, while the step-up coil adjustment specifies the MTT-5571 - and the MTT-5561 sits in the same procedure tables as the chrome option. When a manual's total harmonic distortion check lists MTT-5511, MTT-5561, and MTT-5571 together, it expects the tech to run the measurement three times, once per tape, and compare the results.
The MTT-5561 was also part of a broader Teac test-tape catalog that included speed and wow/flutter tapes (MTT-111), Dolby-B level tapes (MTT-150), DIN reference tapes (MTT-256), and a mirror tape (MTT-902) for checking tape travel. Each tape had its own part number, its own box, and its own narrow purpose. The MTT-5561's purpose was chrome. In the alignment tables for decks like the W-520R, it is the tape specified for channel separation checks, while the MTT-5571 covers adjacent-track crosstalk and the MTT-5511 covers the bulk of the record-bias and level work.
Because it is a tape, the MTT-5561 is a consumable rather than a collectible in the usual sense. It was made to be recorded over, played back, and eventually worn out. A sealed example still exists in its box, and an opened one may have been used to align a deck decades ago and never touched again. Either way it is magnetic tape, and tape degrades. Nobody bought a chromium-dioxide alignment tape to put on a shelf, so any survivor got there by accident.
The MTT-5561 is not playback equipment. It has no meters, no knobs, no head. It is a service tool. Collectors who chase Teac cassette decks sometimes end up with a stray MTT-5561 in a box of accessories and don't recognize it. The part number on the label is the giveaway.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.