The Charm of Recorders. Anyone who has visited our website will certainly have come across images of some reel-to-reel recorders (tape decks). For those of a certain age who are passionate about Hi-Fi, these objects have represented a coveted and fascinating but also often expensive goal. In particular if they were valuable devices for mechanical and sound quality. Those who are younger will probably wonder what these objects were for, given that by now we are used to digital recorders and multifunctional smartphones without mechanics and with a considerably smaller footprint! So perhaps it may be interesting to remember how it works.
Operation in summary
With the device in the recording phase, the electrical signal coming from any source is pre-amplified by an electronic circuit and sent to the recording head (electromagnet). Through the air gap with which it is equipped, a modulated magnetic flux is caused. This flux, in turn, causes the magnetization of the iron oxide particles present on the magnetic tape which, with a constant speed, runs in front of the head, thus forming a magnetic track.
Once the recording is finished and the tape has been rewound, the latter is played again with the device placed in the reproducing phase, thus putting the read head into operation. This works in reverse to that of recording. The magnetic fields present on the magnetic track, recorded with different strengths according to the frequencies, create a weak electric current on the reading head. The signal, pre-amplified or amplified, is sent to the line outputs or to the loudspeakers.
Tape speed
Since the tape runs, great precision is required of all the mechanical parts, responsible for the various phases, whether moving or not. Motors, pulleys, capstans, pinch rollers, head alignment. During the recording/reading phase, the smooth running of the tape must correspond to requirements similar to those of the rotation of the groove of a record and relative reading needle. Great care must also be taken in electronics. For a top result, it is essential to use the same type of magnetic tape used during the calibration of the device. These objects also require good and regular maintenance and dedication and passion in their daily use, virtues that will in any case be amply repaid.
The charm that these recorders convey is, I think, given by the combination of high mechanics with electronics. Quality therefore depends on these two factors mentioned but not only, because the recording and playback quality is also influenced by two other circumstances:
- The speed at which the magnetic tape runs
- The type of recording (2 or 4 tracks)
The higher the speed, the more extended the range of frequencies reproduced as well as the dynamics as the magnetization occurs on a larger portion of the tape. On recorders present in recording studios, 76.20 cm/s (30 inch) is reached. In Hi-Fi you have to opt for 38.10 cm/s (15 inch) which is almost perfect or 19.5 cm/s (7.5 inch) which is mostly used. Then follow the 9.52 cm/s (3.75 inch), the 4.75 cm/s (1.875 inch) and the 2.54 cm/s (0.9375 inch) for lower uses.
2 or 4 tracks recording
Aside from multi-track recorders, in stereo ones we speak of a 2-track recording when the recording head records one channel on the upper half of the tape and the other on the lower half (1=Left 2=Right). Thus the magnetic tape is used only once in the sense of its length with tape expenditure.
On the other hand, 4-track recording takes place when the special recording head first records tracks 1=Left and 3=Right and then (by overturning the tape) tracks 2=Right and 4=Left. So the magnetic tape is used in both directions with tape saving. It follows that in the 2-track system the portion of the recorded tape (magnetic track) is wider than in the 4-track one. This leads to a higher quality of the system.
Open reel magnetic tape
As previously mentioned, magnetic tape consists of a magnetizable layer of iron oxide applied to a sheet of plastic material. The overall thickness is given by the sum of the two. Let’s take the first four reference values for the total thickness from BASF, leaving out the others:
- Standard tape 0,052 mm (52 micron)
- Long play 0,035 mm (35 micron)
- Double play 0,026 mm (26 micron)
- Triple play 0,018 mm (18 micron)
The diameter of the reel remaining the same, the lengths of the last three tapes are greater than the standard one and consequently vary in resistance and flexibility.
With the use of an iron oxide or comparable materials with low background noise (Low Noise), thanks to new working methods that have allowed to increase the magnetic density and therefore the modulation (High Output), a considerable increase in dynamics has been obtained especially when used on 2-track devices.
“The Charm of Recorders”. The fascination still today emanating from these “rotating” devices, connected to a Hi-Fi system worthy of the name, is undoubted and of all importance and so is listening to a well-made analog recording (preferably live or if derived from a master tape) reproduced by a quality, well-maintained device not only on 2 tracks at a speed of 38 cm/s (15 inch), at the top for extended range and dynamics, but also on 4 tracks at a speed of 19, 5 cm/s (7.5 inch). A combination of mechanics and electronics that leaves no one indifferent!