Ferrograph Stereo 808

Additional Info

HAVE you ever pondered, gentle reader, upon the snares and pitfalls which lie in wait for the reviewer, who innocently undertakes to have in his care, for all too short a time, some of the most outstanding products of the electronics industry?
Without a philosophy which enabled him to accept the world for the hard, cruel place that it is, he would become all bitter and twisted, frustrated by the knowledge that, unless he achieved a miracle with his pools coupon, he could never possess such gems of craftsmanship, which only succeed in emphasising the shortcomings of the equipment, “poor things but his own,” with which he must be forever satisfied.
This tape recorder is one such mouth-watering, avarice-raising gem. It’s a dilly, the end, the most, or whatever is the current phraseology for something to shout about – so let’s get on with the shouting.
General description
The recorder assembly consists of a “Wearite ” tape deck, control panel, two identical record / playback amplifiers and power supply bias oscillator unit, each on a separate chassis, interconnections being through plug/socket terminated cables. The units are contained in a strongly-made wooden case, with detachable lid, both finished in a grey-green imitation leatherette, with a strong carrying handle in green plastic and chrome fittings. The deck and control panel are in grey, with grey-green control knobs.
For valve replacement or general maintenance, two retaining screws at the front of the deck can be removed by hand, the deck hinging at the rear to give access to the interior. Layout is compact but uncluttered and assembly and finish are first class. The overall size of the recorder, with lid, is 17½ in. wide x 18¾ in. deep x 9¾ in. high and the weight is 51 lb.
Accessories provided comprise :
6 ft., 3-core mains lead and plug (to fit the recorder); four screened jack plugs; four spare cartridge fuses; a small stiff brush for head cleaning; a roll of adhesive plastic tape, for splicing; and two 7 in. “lock-on” reels, incorporating spring clips in the hubs to grip the ends of the tape, (which allow the recorder to be used either horizontally or vertically).
Also supplied are the main operating instructions, on a stiff, glossy folder, for general reference, and a folder containing full operating instructions, parts list and circuit diagram.
Added to these is the complete “Ferrograph” manual, beautifully printed (with stiff binding), illustrated, covering principles, operation and maintenance of the company’s products generally. This manual may be purchased separately, price 12s.
The following equipment, not supplied with the recorder, is required to complete the installation : – One or two microphones (or a dual stereo microphone), depending on the type of recording required. Two power amplifiers, as the recorder outputs from the two channels are at a low level. Two loudspeakers. (The recorder does not contain audio output stages or loudspeakers.) Headphones, 500 and 5,000 ohms impedance, whilst not essential, are useful for monitoring during recording.
The recorder operates from mains supplies of 103 to 117 volts and 205 to 245 volts, 50 cycles per second, AC only, and consumes 110 watts, The mains voltage adjuster is on the rear panel.
“Tape deck” details
This produces simultaneous, twin-track recordings, for stereo reproduction, or standard, single channel half -track recordings, on the upper track only, so that the normal reel-inversion, two-track type recordings can be made. Three heads are used, viz., upper track erase/ auto-stop, lower track erase and twin-track, in-line, record/playback. Playing speeds used are 3¾ or 7½ ips, the total playing time depending on the size of the reels (max. 8¾ in.) and type of tape used. A 1,750 ft. reel of standard tape giving the following times :-
Mono – 1½ or 3 hours at 7½ or 3¾ ips.
Stereo – ¾ or 1½ hours at 7½ or 3¾ ips.
A continuous loop cassette can be used instead of the standard reels.
Fast rewind, in either direction, takes less than one minute for a full reel and braking is positive and virtually instantaneous. An automatic stop switches off the motors if the end of the tape is allowed to pass the heads, and re-setting takes place when the tape is re-loaded, so that the motors will not run on an unloaded deck.
Cueing indication is provided by a “clock” type tape position indicator, which is shaft driven from the right-hand spool and can be reset by means of a knob at the centre of the dial.
There are five controls on the deck itself. These are: speed selector switch; main function switch, selecting record; fast rewind, fast forward and playback; Start button and stop button (controlling the operations selected by the main function switch); and press button pause control, on the hinged cover over the heads. This has a standard camera thread, so that a shutter release cable can be used for remote operation if required. (The speed selector and main function switch must only be operated when the tape is stationary.)
Tape loading is simple. After the hinged head cover is raised, either fast wind position is selected, moving the pressure pads away from the heads. The tape is dropped into place, connected to the take-up spool, and the hinged cover replaced. Zero the indicator and all is ready.
Adjustable guides control the height of the tape at the input and output of the head cover and the alignment of the R/P head can be adjusted by a screw under the cover.
Wow and flutter is specified as less than 0.2 per cent at 7½ ips.
Amplifier controls and connections
The amplifier controls are on a separate, sloping panel in front of the tape deck, and are duplicated to cover the two channels for upper and lower tracks. Each channel has two input jack sockets. No. 1 for low-level (microphone) signals of about 3.0 millivolts min., and No. 2 for high-level (radio / pick-up) signals of about 300 millivolts min. The gain controls adjacent to the sockets, are operative on both inputs, which have impedances of approximately 500 kilohms.
Microphones and pick-ups, etc., cannot be plugged into sockets 1 and 2 simultaneously, as a plug in socket 2 automatically isolates socket 1, and plugs in either socket disconnect the playback head, which uses the same amplifier, so that all input plugs must be removed for playback
The amplifier output levels, on record only, are monitored by a peak-reading valve-voltmeter-connected so that the needle rises rapidly and falls off again slowly, to enable even the shortest peaks to be noted. A switch below the meter selects either channel and a small knob, to the right of the meter, adjusts zero (with the gain controls at minimum) for each track.
A switch selects the correct response equalisation for the tape speed in use and this is interlocked with the speed selector switch on the deck; if they are each set for a different speed, the motors will not operate.
Output jacks, for connection to external power amplifiers, are at the right-hand side, with the mains on/off switch above. The output impedance, in each case, is approximately 5,000 ohms, to match into amplifiers with input impedances of this amount or greater. The output level is 1.5 volts, approximately.
A neon indicator lamp, on the panel, shows when the recorder is ready for use; this operates from the high tension supply and therefore glows only after the rectifier valve is operative, about 15 seconds after switching on.
A further panel, on the rear of the case, carries the main input plug, mains voltage adjustment and mains fuse (1 amp. for 205/245 volts and 2 amps. for 103/117 volts). An octal socket (valve holder) provides outputs of 250 / 300 volts at 20 mA. and 6.3 volts at 1 amp. (LT centre-tap earthed internally) for ancillary equipment, such as radio tuners, etc, also connections for the Ferrograph Voice Operated Switching Unit, which switches the capstan motor supply and oscillator HT. To complete these circuits when the VOS unit is not in use, an octal shorting plug is provided, from which the spare HT and LT supplies can also be taken. The recorder will not operate with this plug removed.
This panel also carries the mono/stereo switch, which, in the mono position,
cuts off the lower track circuit and controls and switches off the supplies to
the lower track erase and record heads. (In spite of this, some weird effects are obtained if recording is accidentally attempted on the lower track. I know. I
did it – and wondered why the recording was so bad!) A dummy load is switched in place of the erase head to maintain a constant bias voltage.
An erase link is provided, which, when removed, cuts off the erase oscillator output, thus ensuring that existing recordings cannot be accidentally erased if the main selector switch should be moved to the record position, and prevents such movement putting “clicks” on the tape. In addition, a suitable variable resistor can be connected in place of the link, to effect slow fade-out and fade-in of previously recorded material, so that spoken commentaries, etc., can be inserted at random on the tape without the sudden stops and starts associated with the normal erase function.
No tone controls are provided, the equipment having been designed to produce a flat playback response over the full audio range.
Amplifier circuits, etc.
Each playback head winding is transformer coupled to an EF86 pentode amplifier (not used on record), whose output is passed, via input jack 1 to a second EF86. The signal now passes, via input jack 2 and the gain control, to a twin-triode, type ECC81/12AT7, with the two sections in cascade, the amplified signal being fed to one half of a twin triode, type ECC82/12AU7. Output to the recording head is taken from the anode of this stage, through the equalising network, and external output, for the main amplifier, is taken from the cathode. Negative feedback is applied over the last three stages, to reduce distortion.
The recording level meter circuit consists of a rectifier (½ ECC82, diode connected), the circuit constants being chosen to give fast charge and slow discharge of a capacitor across the diode load resistor. The capacitor voltage is then applied to the indicating meter via an amplifier stage (½ ECC82). The circuit has a rapid rise time and true peak indications result.
The frequency response of the overall recorder is 60 to 8,000 cps ±3dB at 3¾ ips and 60 to 14,000 cps ±3dB at 7½ ips, signal-to-noise /hum ratio being greater than 50dB between 200 and 15,000 cps and not less than 45dB outside these limits. On mono operation, the lower track rejection is at least 60dB at 400 cps and on stereo, the track separation is approximately 40dB.
The line-up is completed by an EL84 bias/erase oscillator, operating at about 58 kc/s, and bias traps are included between the amplifiers and R/P heads, to prevent interaction between the amplifiers and the oscillator. A label under the deck gives the correct bias voltage to be used with the particular head fitted.
A full-wave rectifier power unit, using an EZ80, supplies HT for all circuits.
The amplifiers can, of course, be used as ordinary preamplifiers, for microphone or record reproduction, with the tape removed or stationary, and they are adjusted so that the same gain control setting on each amplifier produces the same output levels. If they are to be connected to the main amplifiers through leads exceeding 10 ft. in length, low-loss co-axial cable is recommended for this purpose in order to avoid loss of treble.
If sound-cell crystal microphones, having output impedances between 2 and 5 Megohms, are used with this recorder, a slight loss of bass may result from the 0.5 megohm input impedances, but this can be corrected by means of the tone controls which will, no doubt, be available on the main amplifiers.
Operation and performance
Several mono recordings were made, using standard Zonatape, from microphone (Ronette sound-cell crystal), from radio (“straight” feeder unit) and from records (Collaro 4T /200 transcription), and in all cases the results were excellent, reproduction via tape being indistinguishable from direct reproduction of the original.
A stereo recording was made, but although the results were satisfactory electrically, they were not so hot aesthetically as the sound sources available were rather limited! However, reproduction of an H.M.V. stereo tape (“Philharmonic Pops” by the Sinfonia of London), was most impressive and enjoyable. Unfortunately, the reproducers used were not identical assemblies and strong suspicions were aroused that the acoustic levels differed, so that these had to be adjusted by varying the electrical levels – not strictly according to Hoyle!
With the comprehensive instructions available, no difficulty was experienced in operating the recorder, but a couple of small snags did come to light. The standard plastic reels, supplied with the tapes used, do not sit quite so far down the spool spindles as do the Ferrograph reels, so a slight misalignment resulted, causing the tape to rub occasionally on the reel peripheries.
The other point was that operation of the main selector switch on the deck produces a loud “twang” from the springs in the mechanism, so that if recording from microphone in a quiet place, it is advisable to wait a moment after selecting “record.” Alternatively, this may be overcome by keeping the microphone well away from the machine, before pressing the start button, otherwise the dying twang is recorded.
It may cross your mind that the claimed frequency response for this equipment is little or no better than that claimed for some of the much cheaper recorders, but remember that specifying response alone is pointless without the amount of deviation from the mean level being stated, and many manufacturers claim wide responses and give no levels -a misleading practice. “Response down to 30 cps” may mean with the accent on the “down “! – by a large drop in level. The claimed frequency response for this recorder is confirmed on test and can be relied upon by the user.
Actually, a much wider useful response is available.
It is a recorder. to satisfy the most critical amateur, or professional and its choice by many of the most exacting users is recommendation enough..
Manufacturer’s Specification
Price: 105 guineas
Mains supplies: AC only. 103-117 V and 205-245 V, 50 cycles.
Power consumption : 110 watts.
Recording sense : Twin-track–either simultaneous or upper track only.
Track width: 0.085 in
Playing time (standard tape) : MONO – 1½ and 3 hours at 3¾ ips.
STEREO 45 minutes at 7½ ips; and 1½ hours at 3¾ ips
Frequency response: 60-8,000 cps ±3dB at 3¾ ips. 60-14,000 cps ±3dB at 7½ ips.
Wow and flutter: Less than 0.2 per cent at 7½ ips
Input levels: 1 – 3.0 mV rms (min.) 2 – 300.0 mV rms (min.)
Input impedances: 1 and 2: 0.5 Megohms (approx.).
Output levels: 1 and 2. 1.5 V (min.) into 5,000 ohms or greater (cathode follower).
Signal-to-noise ratio : Better than 50dB from 200 to 15,000 cps (45dB min. overall)
Track separation (stereo) : 40dB (approx.)
Lower track rejection (Mono): 60dB minimum at 400 cps.
Dimensions: 17½ x 18¾ x 9¾ in. (with lid)
weight :51 lb.
Makers: The British Ferrograph Recorder Co. Ltd., 131, Sloane Street, London, S.W.1.