Category:Mid High Fidelity
Country of Manufacture:United Kingdom
Release dates:1960 - 1963
Speeds: 3 3/4, 7 1/2, 15
Max Reel Size("): 7"
Number of heads: 3
Dimension: 21 x 18¼ x 15" (503 x 460 x 365mm)
Head Composition: Permalloy
Head Configuration: Stereo
# Motors: 1
Frequency Response:(all ± 2 dB): 15 ips: 50 to 15kHz
Wow and Flutter:0.2% RMS at 15 ips. 0.25% RMS at 7½ ips and 0.3% at 3¾ ips
Sound quality rating:7 / 10
Long-term reliability rating: 7/ 10
Weight: 80 lbs (36kg)
The TR52 was produced in various versions, single channel full or half track (TR52/1) and two channel (TR52/2). In addition, each variant came in two versions depending on tape speed, “C” for 3¾ and 7½ ips and “D” for 7½ and 15 ips. The model pictured here is a TR52/2C
Marketed as a professional model, record characteristics were set up in accordance with CCIR recommendations and separate record and replay amplifiers and heads permitted “off-tape” monitoring.
A single motor connected to the capstan assembly via a flexible coupling also provided power for the take-up, rewind and wind-on facilities.
Speed variation: less than ±0.2% over a full reel / Dynamic range: unweighted noise and hum 50dB below peak recording level / Total harmonic distortion: less than 1% 2nd harmonic and less than 2% 3rd harmonic at peak record level / Crosstalk: better than 40dB at 1kHz / Record characteristics: CCIR specification for 15 ips and 7½ ips / Bias frequency: 100kHz approximately / Valve complement: 3 x EF86, 2 x ECC83, 2 xECC82, 2 x ECC81, 6BW6, EZ81 / Rewind speed: 2 minutes 20 seconds in either direction for 1,800ft / Audio output power: 2 watts at 3 to 5 ohms. / Recording level meter: selectable for line in, record, line out, bias or erase on either channel / Inputs: Mic – balanced bridging suitable for 30 – 50 ohm microphone – sensitivity less than 10mv for peak Line – ‘Floating’ for balanced or unbalanced working, suitable for 600 ohm impedance, 80mV. / Outputs: Line – 600 ohm ‘Floating’ balanced or unbalanced, maximum level +20dB extension speaker / Speaker(s): internal 5″ permanent magnet speaker
taken from The Tape Recorder, May 1960
A GLANCE or even a close study of performance Specifications is rarely of much value in indicating the performance of a tape recorder for, as with many other products, the less scrupulous manufacturer prepares his specification after looking at his competitors claims and hardly bothers to take measurements on his own machine. This is the real disadvantage in presenting technical data to the public, for a good sales manager can easily improve the performance even if the designer finds it difficult.
There are many machines at prices below £60 with a performance that, judged solely on advertising claims, appears to be superior to the tape recorders used by professional recording engineers.
However, Specifications are of value in indicating the facilities provided, for this leaves little scope for the sales manager’s inventive genius. In some respects the facilities provided by the TR.52 are unusual even in professional machines. It is a two track recorder, but the ” electronics ” include two separate record
and replay systems with the switching sufficiently flexible to allow one track to be used for recording while the other track is being used to replay some previously recorded program.
The VU meter can be switched to check the bias erase, the incoming signal, signal being recorded, or signal going out to line. An internal monitor speaker can be switched to check the incoming signal, the signal being recorded, or the outgoing signal. A monitor amplifier having an output of 3 watts drives the monitor speaker, but the performance is sufficiently good to justify the use of a high quality external speaker where the space is available. Separate output jack sockets, transformer coupled into the output stages, provide a maximum signal of about 7 volts across 600 ohms from each replay amplifier. Microphone equalization is introduced by a three position switch in each channel giving a loss of 0 dB, 5 dB and 10 dB.
Constructionally the TR.52 is unusual in that five separate electronic chassis are provided, interconnected through plugs and sockets that allow the individual units to be withdrawn and replaced in a couple of minutes in the event of a failure. This is undoubtedly an expensive technique but it is invaluable in professional work.
There is space for two 8¼ in. spools, the tape path between them being indicated by white lines on the surface of the deck. This is a useful idea for the tape path is somewhat unusual. Distorted spools are the rule rather than the exception, but as an aid to dealing with this problem, a flanged guide pulley is mounted to control the height of the tape as it enters the take-up spool, a knurled knob providing height adjustment. This is one of the small refinements that assist in obtaining low values of wow.
The head assembly is also unusual for it contains no less than six heads. It has been noted that there are two separate record and replay systems allowing two tracks to be recorded simultaneously. This necessitates two erase heads, one half-track head erasing the top track and the second a full-track head erasing both tracks. These are followed by two record heads and two replay heads to allow the signal being recorded on the tape to be continuously monitored while recording is in progress. The head assembly cover carries two controls, a small lever which selects full-width or half-width erase and a knob which moves the tape on to the replay heads during high speed winding to facilitate cueing.
In front of the deck is a small sloping panel carrying all the monitoring controls and, as already indicated, the monitoring facilities are unusually thorough. A centrally mounted VU meter can be switched to read the input signal, the signal being recorded, or the signal leaving the recorder, a separate switch allowing either channel to be monitored. On the right hand side of the control panel are further switches that allow the monitoring amplifier and speaker to be switched to either channel to check ingoing and outgoing signals or the signal at the recording head.
Operation is facilitated by grouping all the signal controls on another small panel in the front of the machine. This carries two input and one output jack socket for each channel, together with the recording level and replay level controls, the jacks, knobs and switches in each channel being arranged in one vertical line. The two input sockets for each channel allow the use of a low impedance microphone coupled in through a screened and balanced transformer, and for a signal to be taken in from a 600 ohm line through a balanced transformer, but the two signals cannot be mixed through the controls provided A separate input pre-amplifier ensures that there is sufficient gain for any ordinary microphone, only 100 microvolts being necessary to load the recording amplifier fully.
Separate pre-set gain controls on all the record and replay amplifiers allow the relative gains to be set to ensure that the signal output from the recorder is the same as the signal input when record and replay gain controls are set to the same positions.
The machine was put through the standard test routine with the following results.
Frequency Response: When replaying any of the commercially recorded tapes the replay response only is involved. Both channels were checked, using the EMI, professional test tape SRT.13, the response of channel 2 being shown in fig 1, though channel 1 did not differ from channel 2 by more than 1 dB at any point in the frequency range, and in fact the two response curves were within 0.5 dB over practically the whole range. The performance was not quite so good when recording and replaying, the result being shown in fig. 2. It will be seen that the frequency range is not particularly wide, but within the range it is remarkably smooth, an aspect of the performance which is given too little weight in current advertising claims.
There is no standard recording characteristic for a tape speed of 3¾ i/s, and EMI, make no wild claims for an ultra-wide response at this speed, but in fact the figure of -3 dB at 40 Hz and 8 kHz claimed was not met in the test machine as the curves of fig. 3 show.
It may be a significant comment on current advertising that neither of the professional machines recently tested had a frequency response comparable in bandwidth with many domestic machines, though both showed lower fluctuations within the range than the domestic machines with greatly improved signal to noise.
Signal/Noise Ratio: The ratio of the measured signal at the 2% distortion point, to the noise remaining after wiping a fully modulated tape, is shown in Table 1. The values are particularly good and would no doubt have been several dB higher if the tape had been as fully modulated as is usual in domestic machines where higher distortions are tolerated.
Wow and Flutter: Wow and flutter were measured for two conditions at each tape speed. When replaying a commercially recorded tape the total wow and flutter is substantially that due to the replay machine, for the wow in studio machines is very low in comparison. To simulate this condition the wow and flutter was measured using a 3 kHz tape recorded on a studio-type machine. When recording and replaying on the same machine the drive disturbances appear twice, once on record and once on replay. This condition is obtained by recording and replaying a 3 kHz tone on the machine under test. Both sets of figures are quoted in Table 2, from which it will be seen that the performance is remarkably good. An aspect of this that is not shown up by the quoted figures, is that the total wow and flutter varies very little as between the start and end of a reel, nor did it exhibit any great variation from instant to instant.
Sound quality is soft and smooth without a trace of harshness and is easy to listen to for long periods. As might be expected from the S/N figures, background noise is exceptionally low. Sound quality when recording and replaying is very good indeed, no doubt due to the low values of wow, flutter and harmonic distortion.
Mechanically the machine is quiet and free from any undue vibration, even when rewinding at high speed. Most users would undoubtedly prefer push-buttons to knobs, particularly on the high speed wind and record-replay controls which are a little on the stiff side.
The TR.52 has a professional performance, but it will also appeal to the amateur who appreciates the degree of perfection achieved and can afford the rather high price.