|Home | Audio Magazine | Stereo Review magazine | Good Sound | Troubleshooting
Departments | Features | ADs | Equipment | Music/Recordings | History
by Donald Aldous
ALTHOUGH 1972 already accuses some distances from its birth, I risk it nevertheless to reiterate with intensification the best wishes for a successful, troublefree, and pleasure creating year. It represents, incidentally, the thirteenth year of UIPRE's existence. Therefore, it must be a happy one. Full of confidence we have chosen Papier Rose' for the receipt stamp offering it in exchange to the active members who will clear their membership fee 1972 .... With these thirteen years we are definitely in advance of British people, who-as statistics seem to prove-face only 12 years of their life their television screen! "1972 has too the quality of increasing the distance from Emperor Nero's reign (you remember the incendiary at Rome). This money-voracious person had introduced a special taxation based on the protuberance of human's belly (I suppose pregnant women excluded); the more prominent, the higher the tax! ... But the UIPRE is "rounding" its belly without hesitation." No, this is not the quaint language seen in some English translations of Japanese, but appears in the official Bulletin No. 133, January, 1972, issued by Mr. Karl Pinsker, General Secretary, Union Internationale de la Presse Radiotechnique et Electronique (UIPRE). I wanted to start this letter on a cheerful note, and Karl, as a person is as delightful and friendly as his eccentric English suggests. His puns on English words and phrases have to be heard to be believed, but his contribution to keeping the UIPRE organization running is notable and, in my view, irreplaceable.
In case you are not familiar with this association of editors, publishers, and contributors to radio--technical and electronic periodicals, the objects of the body are to achieve close communication between members in their professional capacity and to promote mutual understanding by personal contact, to assist in the dissemination of reliable technical information on relevant subjects, and to give mutual help in solving professional problems.
As many professional audio engineers and authors must read this paper, if you are not a member, why not get details from: Mr. Karl Pinsker, UIPRE, CH. 4002, Basel, Switzerland, P.O. B. 1027.
Most television receivers in this country make no provision for taking off a sound signal safely from the circuit, and in consequence many owners of hi-fi equipment have been unable to take advantage of the high quality sound that is transmitted these days by the BBC and ITV (Independent Television companies) in the UK. There are, of course, acoustic and technical studio problems associated with TV sound and picture transmissions that are not present in purely sound transmissions by radio, but it is estimated that the sound quality of about 95% of British television receivers is comparable only to the performance for this parameter of a medium-wave portable radio set.
Sound, as the poor relation of the TV medium, was debated vigorously at a recent discussion evening in London, organized by The Royal Television Society. Obviously, much of the problem revolves around the limitations inherent in 7-x-5-in. or 5-x-3-in. loudspeakers and output stages of 1 or 2 watts.
Now that Great Britain has substantially nation-wide coverage with TV signals from UHF transmitters (using the PAL color system common in Europe), Continental and Japanese manufacturers are casting eyes at '' British market. Some of these 62' UHF receivers have feat unknown in British TV sets, such as, large loudspeakers (two or more), tone controls, and higher undistorted power outputs. To be fair, some British companies are recognizing this need, and, for example, Decca has models with double-wound a.c. transformers, tone controls for main amplifier, and a low-level output signal at low impedance to feed to any hi-fi system.
Despite the fact that most British TV sets are now transistorized or hybrid types (tubes and transistors), the circuits are still a.c./d.c. principle, and are not fitted with an isolating transformer, so it is unsafe to attach external leads for loudspeakers or hi-fi feeds. A few so-called audio adaptor units have been marketed here, which incorporate double-wound isolating transformers, but the answer to this problem may well be in a new device (one version of which is called Telefi) which by utilizing stray emissions from the TV receivers, obtains a clean sound signal largely unaffected by the quality of the TV circuitry.
More precisely, this technique depends on the presence in the vicinity of UHF sets (or the UHF section of a dual 405/625 line set) of electromagnetic radiation from the intercarrier sound i.f. signal. This is at a frequency, in the UK, of 6MHz. The magnetic component of this field can be picked up on an induction coil (or probe) affixed to the outside of the TV cabinet by sticky tape, for example, and the signal is then fed to the radio or auxiliary sockets of the hi-fi equipment.
This method means that there is complete safety, as there are no direct electrical connections to TV chassis nor modifications to the TV set, and hence makers' guarantees are not invalidated nor are rental agreements on hired TV sets. In some tests we have done, the encapsulated probe coil (to which is attached a length of screened cable, up to 30 ft. long) was located near to the back cover of the set, as close to the sound i.f. amplifier as possible, and on the receiver we employed the field was so great that position was not critical for good results.
The audio output of the unit is adjustable between 100mV and 1 V by a preset, and the output impedance is 2,000 ohms. Distortion is stated to be less than 1%. The Telefi costs about £24 in UK, or $62.65 approx., and is manufactured by Dinosaur Electronics Ltd., 85 Victoria Street, Windsor, Berkshire.
There are other approaches to this problem, including a Swedish system which converts their 5.5 MHz inter carrier sound i.f. to a frequency of 10.7 MHz thus permitting it to be fed into the i.f. section of a normal FM tuner, but a friend and colleague of mine, Gordon King, one of the most prolific technical writers on audio and electronics in the world, was actively experimenting with these methods as far back as early 1967.
Gordon's method was to demodulate the sound signal from the intercarrier signal, then to process it and apply it to an FM very low level VHF oscillator producing a signal at a frequency corresponding to a quiet spot on Band II. The little unit was battery-powered and there was no physical connection between the TV set and the FM tuner.
Indeed, there were no controls, other than an ON/OFF switch, and the neat box was merely placed on the top, side or back of the TV set for optimum intercarrier pickup, that is, best S/N ratio, and the FM tuner adjusted to the FM carrier from the low-level oscillator, successful in past years. On the Continent, the Paris Festival du Son was due to be held between March 9th and 14th but, at time of writing, no venue announced. Some 50 brand names were Alas, when the Radio Services Department of the British Post Office was approached to discover the legality of such a device (a mini-transmitter), it was ruled that the device would require a license as it would involve the use of "wireless telegraphy" and such a license would be unlikely to be granted, even at such low powers. It was permissible to transmit the FM television signal via a coaxial cable link, but since this would have required a diplexer (to introduce the normal FM aerial), radiation problems might still exist. So the system was not produced commercially, but Gordon's work is worthy of going on record, I think. It would be interesting to know whether any similar devices have been marketed in America.
Springtime produces its crop of audio exhibitions, and March saw the public address and sound reinforcement show, organized by the Association of Public Address Engineers, and Sonex '72, both held in London, with the latter at the Skyway Hotel, near London's Heathrow Airport. This might seem an odd venue, but in fact the rooms are well soundproofed and the exhibition has been down to take part in the Sonex '72 show, and a series of Sound Seminars were being arranged by myself and colleague Frank Jones. Yes, there's a boom in hi-fi in Great Britain at present, and the audio scene looks set fair for quite a while.
This letter is being compiled before any of these exhibitions, so much detail of new products or developments is not yet released. However, I can mention that Radford's new range of loudspeakers, mentioned in passing in last feature (October, 1971), including the novel 360° mini-model, will be released, together with new speaker designs from Rola-Celestion and B & W. This latter model is known as the DM2 and has been two years in gestation. It has a very high standard in terms of frequency linearity, freedom from coloration, and is capable of handling relatively high powers. In fact, John Bowers tells me that it has been created as an international product, aimed at the Canadian and American markets, with their high power handling requirements.
I am however, able to release some news of a new cartridge from Decca, christened "The London." This model is the result of five years research to produce a virtually hum-free cartridge using the so-called "positive scan" (no cantilever) technique used in the well-known Decca ffss pickup heads.
Hum pickup from the fields around turntable motors, transformers, motor switches, and main leads has represented a problem with earlier Decca cartridges, and the new design incorporates a revolutionary type of magnetic material used in the magnetic circuit.
The manufacturing technique includes super-cooling the armature in liquid nitrogen at minus 196°C. to produce an outstandingly flat response and stable overall performance. The design has also brought about a significant reduction in the cartridge mass, from about 14 grams to less than 4 grams. The output of the cartridge is also increased to around 7 1/2 mV at 5 cm/secs.
Lastly, an important tid-bit of quadraphonic news in the UK-EMI, the giant record and electronics combine, has joined forces with CBS to produce stereo/quadraphonic LPs using the Columbia SQ technique. These compatible disc records will be released, in a small number, around Sonex '72 period, and tape cartridges using the same system will be issued at roughly the same time.
(Audio magazine, May 1972)
= = = =
Prev. | Next