is it metal tapes where you can never quite record over them, you can always hear what ever you recorder first time? i know that happened with a few of the more expensive maxell tapes i had
wiki:
At about the same time,[
when?]
chromium dioxide (CrO2) tape, later designated Type II, was introduced by
DuPont, the inventor of the particle, and
BASF, the inventor and longtime manufacturer of magnetic recording tape.
[37] Next,[
when?] coatings using
magnetite (Fe3O4) such as
TDK's Audua were produced in an attempt to approach or exceed the sound quality of
vinyl records.
Cobalt-
absorbed iron oxide (Avilyn) was introduced by TDK in 1974 and proved very successful. "Type IV" tapes using pure metal particles (as opposed to oxide formulations) were introduced in 1979 by 3M under the trade name Metafine. The tape coating on most cassettes sold today as either "Normal" or "Chrome" consists of ferric oxide and cobalt mixed in varying ratios (and using various processes); there are very few cassettes on the market that use a pure (CrO2) coating.
[2]
Simple voice recorders and earlier cassette decks are designed to work with standard ferric formulations. Newer tape decks usually are built with switches and later detectors for the different
bias and
equalization requirements for higher grade tapes. The most common, iron oxide tapes (defined by the
IEC 60094 standard
[3] as "Type I"), use 120
µs equalization, while chrome and cobalt-absorbed tapes (IEC Type II) require 70 µs equalization. The recording "bias" equalizations also were different (and had a much longer time constant). BASF and
Sony tried a dual layer tape with both ferric oxide and chrome dioxide known as 'ferrichrome' (FeCr) (IEC Type III), but these were available for only a short time in the 1970s. These also use 70 µs, just like Type II did. Metal Cassettes (IEC Type IV) also use 70 (or '50' on few decks by Luxman and Alpine) µs equalization, and provide still further improvement in sound quality as well as durability. The quality normally is reflected in the price; Type I cassettes generally are the cheapest, and Type IV are usually the most expensive. BASF chrome tape used in commercially pre-recorded cassettes used type I equalization to allow greater high-frequency dynamic range for better sound quality, but the greater selling point for the music labels was that the Type I cassette shell could be used for both ferric and for chrome music cassettes.
Notches on top of the cassette shell indicate the type of tape. Type I cassettes have only
write-protect notches, Type II have an additional pair next to the write protection ones, and Type IV (metal) have a third set in the middle of the cassette shell. These allow later
cassette decks to detect the tape type automatically and select the proper bias and equalization. Virtually all recent hi-fi systems (with cassette decks) lack this feature; only a small niche of cassette decks (hi-fi separates) have the tape type selector. Playing Type II and IV tapes on a player without detection will produce exaggerated treble, but it may not be noticeable because such devices typically have amplifiers that lack extended high-frequency output. Recording on these units, however, results in very low sound reproduction, and sometimes distortion and noise is heard.
Also, these cheaper units cannot erase high bias or metal bias tapes. Attempting to do so will result in an incomplete erasure. This is due to the fact that the bias levels for high and metal position requires greater levels.
