Dynatron STR1

Additional Info

Tape Recording Magazine, March 1967

DYNATRON STRI investigated by R. Hirst and D. Killick
THE Dynatron STR is a most unusual and interesting piece of equipment. Offering full quarter-track stereophonic record playback facilities, it has an audio output available via extension speaker sockets, one for each channel, together with a single, small built-in speaker for monitoring purposes. The tape transport system is a new Garrard deck operating at 1 7/8, 3¾ and 7½ ips. Three heads are provided, one each erase, record and playback. Full multiplay facilities are available and the machine can also be used quarter-track monaurally or the two channels of a stereo signal can be combined.
Design has obviously been influenced by the manufacturer’s intention to produce a stereo recorder whose prime function is to form an accessory to an existing hi-fi or good quality radiogram installation. We therefore find that the mechanism is enclosed in an attractive teak cabinet without the usual lid or handle, and the cover provided is in a substantial, flexible, transparent plastic. The machine may be regarded as following the recent trend for ” unit hi-fi” equipment. Not least interesting is the price of 79 gns., which is a remarkably low figure for the facilities provided.

We have set out above our own findings on technical investigation and these are shown in tabular form so they may be compared with the manufacturer’s specification. For some reason the manufacturer has omitted to quote tolerances relative to frequency response. The mere ability to reproduce certain frequencies is meaningless if this is not related to the rest of the audio frequency spectrum. In the present instance the manufacturer’s reticence is quite unnecessary because, as our figures show, the tolerances are exceptionally good. Readings were taken with the push-key tone controls set at minimum for bass and maximum for treble. Distortion level at 3.9 per cent is rather less good than the frequency response, but the manufacturer assures us that all machines now being dispatched are modified to considerably improve the distortion level.
The signal to noise ratio is exceptionally good. apart from a noticeable deterioration at 50 cycles which indicates mains hum. Even at this frequency. however, the signal to noise ratio of – 48 dB unweighted below the peak output level may be regarded as very acceptable. The wow and flutter figures conform to the general high standard expected of modern equipment, and the cross talk level is exceptionally good.
Following the technical investigation we proceeded to carry out a number of user tests. The first point that immediately became obvious was the fact that in spite of the provision of a separate playback head there is no facility for “after record” monitoring. Monitoring is possible either through the external speaker outlets or by means of the internal speaker itself which may be switched between channels. The sound heard will, however, be the signal that is fed into the equipment, and not the playback of the tape. Although a desirable facility for live recording, after record monitoring is not so essential for purely hi-fi applications and doubtless this, coupled to the remarkably low retail price, influenced design.
We must take the manufacturer to task for permitting the treble tone control to operate in the record mode. The separate tone controls, treble and bass, are in the form of push keys giving top cut on the one hand and bass boost on the other. It is most unusual with modern equipment to find tone controls operative during record. When this does occur the tape produced will deviate seriously from the standard CCIR or NARTB recording characteristic and would require severe tonal corrections on a playback machine if it were to be reproduced correctly. With the Dynatron STR 1 it is essential that the treble control key should be in its maximum position as otherwise the recording itself will suffer top cut. Unfortunately there is a danger that this control might be left in the wrong position accidentally, in which case poor quality recordings would inevitably result. Apart from this criticism (which is the most serious one we have to make about the Dynatron STR1) we do feel that conventional variable tone controls are much superior to the push key cut employed here where the choice is literally between “all or nothing.” When used in conjunction with other hi-fi equipment the recorder should be set for a flat response; fine tonal adjustment would be carried out by means of the controls in the main amplifier.
We could also criticise the very smooth finish to both the track selector knob, which makes it difficult to turn, and the ganged volume/record level controls which make the setting of levels rather difficult.
The Garrard deck tends to be noisier than we would have cared for and does take an unusually long time to reach full running speed at 7½ ips after the start key has been depressed. This “run in” time could result in the slurring of the opening passages of a recording. This can be obviated, however, by use of the pause control which does give an almost instantaneous start. We found that the start key on our deck was not as positive as we would have liked. It had an intermediate position where, although it felt and sounded as if the tape were being driven, the key required further pressure to actually engage the capstan.
These criticisms are really on minor points which must be considered in relation to the cost of the machine, When we came to record we were pleased to note that the two quadrant type, edge meters (one for each channel) were sensibly illuminated and readings were clearly visible. A stereo recording was taken at 7½ ips from the new BBC multiplex transmissions using an Armstrong integrated tuner-amplifier, type 127, fitted with multiplex decoder. There was no audible interference on playback from the carrier frequency, neither was there any audible beat with the recorder oscillator. For playback the recording was reproduced by driving a pair of external speakers from the extension speaker sockets and quality was found to be wholly acceptable. By connecting the low level output provided in the combined “radio input” socket to a high quality amplifier we achieved very good quality indeed.
This machine will doubtless be used for the reproduction of tape records and so we proceeded to play back a selection of E.M.I. pre-recorded tapes. As might be expected from the quoted figures for playback response, the sound quality was better than one should legitimately expect from such a comprehensive piece of equipment that has obviously been designed and built to a very reasonable price, and the background noise was almost nonexistent. We did not evaluate from the internal speaker as this is only intended to perform a monitoring function.
Our conclusions on the STR I are that the manufactures has achieved what be set out to do-to produce the best obtainable quality within a price bracket that should be well within the reach of most people. As such it offers extremely good value for money and should be seriously considered by all who are thinking of adding tape to an existing set-up. Alternatively it could form the nucleus of a full stereo installation in view of the very wise provision of audio output on the two external speakers sockets. Of smart. modern appearance, it will also look well in any living room.