Brenell Engineering Mk 5 stereo

Additional Info

Tape Recording Magazine, May 1962
WHEN a tape recorder performs exactly as the manufacturers claim it will do, there is little more to be said by the reviewer, and this recorder is a case in point. It does precisely what it is supposed to do and does it well.
After extensive use, not a single defect has been noted and using it was a pleasure. Admittedly, at 88 guineas it’s a bit expensive, but it is value for money, which is more than can be said for some costly recorders.
It is self-contained, in a mottled-grey, plastic-covered wooden case, with detachable lid, the overall size being 18 x 17 x 9 inches, and it weighs 40 pounds. Two sliding doors in the rear of the case give access to a compartment for microphone and mains lead stowage and a panel on which are mounted the mains on /off switch, fuse, and voltage adjuster.
The recorder operates from 50 cps mains supplies of 210/240 volts (or 110 volts, to special order), the total consumption being 120 watts. It is supplied with a reel of tape, but no microphone, sufficient gain being available in the recording amplifier for any type preferred by the user. A red lamp on the front panel indicates when the recorder is “ON.”
Assembly
The recorder is divided into three units. The tape deck, a power supply and bias oscillator unit, which is fastened to the bottom of the case, and an amplifier unit, which is mounted on a separate control panel on the front of the recorder.
This is only the second machine I’ve met in which maintenance has been simplified by careful design. Removal of the amplifier section is simplicity itself. Only two screws to withdraw at the ends of the panel and the unit lifts out in one piece. The leads are long enough to allow it to be examined with the deck and power supply still in case. No struggling with the whole assembly just to change a valve or component, or make some slight adjustment.
(Have you ever tried to operate a tape recorder upside down, in order to trace a fault? If you have, you’ll understand my enthusiasm for this design). Full marks for easy servicing of the amplifier section.
Tape Deck
This is a twin-track, three-motor deck, of Brenell’s own design, giving speeds of 17/8, 3¾, 7½ and 15 ips. Two interchangeable brass bushes, of different diameters, are provided for fitting on the capstan motor spindle, the smaller giving the first three speeds and the larger, the last three. A three-position speed control, on the deck, is marked for both ranges.
Other controls include a record/off/ playback switch, with a safety interlock to prevent accidental selection of “record;” a pause button, which disengages the tape from the capstan; a superimpose button, which lifts the tape from the erase head; and a fast forward / rewind switch, which can only be operated when the R/P switch is in the centre (off) position. Also included is a tension control which enables extra braking to be applied to the take-up spool on rewind, so that the tape, which is lifted away from the heads on fast wind, is wound tightly and securely on to the feed spool.
The maximum spool size useable is 8½ inches and 1,200 ft. of tape can be rewound in 45 seconds. Braking is positive, but not vicious and there is no tape spillage.
There are separate heads for erase, record and playback, the R/P heads having independent azimuth adjustment. After leaving the heads, the tape passes round a nylon pulley, which has height adjustment, so that it can be set to feed the tape on to take-up spools of different kinds without the risk of rubbing the edges of the tape. The pulley also reduces friction on the tape face during operation.
A digital rev. counter-type tape position indicator, driven from the take-up spool spindle, completes the deck assembly. Track sense is to international standards, i.e., upper track moving left to right. Wow and flutter figures are as follows: Less than 0.25 per cent at 17/8ips; 0.15 per cent at 3¾ ips; 0.1 per cent at 7½ ips, and 0.05 per cent at 15 ips.
Power Supply Unit
A transformer and EZ80 valve rectifier, followed by resistance/capacity smoothing, provide 300 volts H.T. and valve heater supplies. Connections to the deck and amplifier unit are by means of cables fitted with plugs and sockets, for ease of assembly and removal. An EL84 pentode valve oscillator provides the erase and bias signals, the latter being adjustable for optimum performance.
Amplifier Unit
Separate amplifiers are provided for record and playback, each assembled on a small chassis. These are fastened to the control panel, with a record-level meter between them. It is thus possible to monitor through the playback amplifier whilst recording is taking place, and, if the signal source is a microphone, echo effects can be produced by picking up the delayed sound from the loudspeaker, the amount of the delay depending upon the tape speed in use.
The recording amplifier consists of an EF86 pentode coupled to a 12AX7 twin-triode, with both halves in cascade, the output feeding the record head and a monitor socket. (Impedance, 2 Kilohms min.) Another 12AX7, with one half diode connected, acts as rectifier and control valves for the record level meter, which has a right-hand zero movement.
When the recorder is operative, the needle swings to the left and zero record level is then set by means of a control just below the meter, with the input gain controls turned fully off. Over-modulation is indicated when the needle reaches a red section at the right-hand end of the scale.
Input sockets are provided for microphone and radio/gram, each with its own gain control to enable programmes to be mixed. The impedance of the microphone socket is 1 megohm, with a sensitivity of 3 millivolts. The impedance of the radio socket is 0.5 might, with sensitivity of 300 millivolts. A four-position switch selects the correct equalisation, for each tape speed, on both the record and replay amplifiers.
The replay amplifier has four stages, consisting of an EF86 pentode, a 12AX7 twin-triode, and an EL84 output pentode. The response is from 25-25,000 cps dB, and the output power approximately 2½ watts. It incorporates independent bass and treble controls, the former giving a variation of ±6dB at 70 cps and the latter ±6 dB at 15,000 cps. There is also a socket for an external (15 ohms imp.) loudspeaker, the internal ‘speaker, a 9 x 5 inches elliptical unit, being muted when the external one is in use. The above frequency response does not, of course, include the internal loudspeaker.
As there is an input socket for external signals, with an impedance of 1 megohrn and a sensitivity of 30 millivolts, connected to the first half of the 12AX7, the replay amplifier may also be used for low-power, HI-FI reproduction of records, etc. If it is desired to use the recorder with an external amplifier, a frequency-corrected 200 millivolts output signal, at 50 Kilohms impedance, is available at another socket, fed from the output of the second stage. With a pair of high-impedance headphones, this socket can also be used for low-level monitoring. It does not mute the amplifier output, so that the playback gain control must be turned to zero if no sound is required from the loudspeaker.
The frequency response range of the overall recorder, lower register at 40 cps, is up to 20,000 cps at 15 ips, with restrictions at 18,000 cps, 13,000 cps, and 6,000 cps respectively at 7½ , 3¾ and 17/8 ips. All figures ±3dB.
General Comments
No difficulty was experienced in familiarising myself with the recorder and putting it into operation. A clearly-written handbook is provided and all sockets and controls, except for the on/off switch, are on the front panel, making connections easy. The handbook, incidentally, gives some useful tips on the choice and use of external equipment.
Within a few minutes of removing the recorder from its packaging, it was quietly recording a radio programme as a first test and the result was very good—even more so when an external loudspeaker assembly was connected.
Replay through an external HI-FI amplifier was quite impressive, and further tests with other sound sources gave results which demonstrated clearly that this recorder, particularly at the faster speeds, is something out of the ordinary.
Even the slower speeds give good enough reproduction of music to satisfy most listeners, but this is a connoisseur’s recorder, capable of satisfying the most critical ear.
Subsequent frequency tests, simplified by the use of a bias-signal filter and some useful tips on test methods, kindly supplied by the manufacturer, confirmed that the performance was well up to specification. Careful layout, screening and choice of components have kept hum and noise to a very low value, the point at which hum became apparent being the point at which the audio signal blasted the eardrums!
The results are as clean and satisfying as its appearance, full justice being done to any sound source the user cares to choose. As I have already said, it does just what it’s supposed to do and does it well. Further comment in this direction would be superfluous.
I have only one small criticism of the design. The head cover is in two parts, the rear one being detachable by means of an upward pull. The ends of this section are tapered, parallel with the deck, with no rear “drop,” and make ideal grips for lifting the cover, but they feel as if an uneven pull or a sudden sticking of the fixing pins would cause them to snap, and a little strengthening here could be advantageous.
Apart from that minor detail, it’s a very fine recorder, and if you can persuade your nearest and dearest to buy one for you, you’re a luckier man—or woman-than I am!
Specification
If I listed all the performance figures, assembly details and the comprehensive facilities, it would take almost as much space as the rest of the article, so you’re not going to get all the information from a quick look at the end, this time. You’ll just have to resign yourself to reading from the beginning. Well worth it, I assure you. Try it. Ready ? Go.
“When a tape recorder performs …