A Beginner`s Guide To Hi-fi

Transcript

25p AUDIO T SUITE 16 – D 119 OXFORD STREET, LONDON, by J. R. Hey A.S.E.R.T. MAIL ORDER &: PERSONAL EXPORT DIVISION , Telephone - 0 1-437 5338/8) 91 / 3063 Han/..Uf.- --Lloyds Bank. 123 Qxford Street London, W.I SYMBOL HANDBOOK SERIES A BEGINNER'S GUIDE TO HI-FI By J.R. Hey A.S.E.RT © 1969 P, ;nutd Olfset Litho by Walden Business Service •• Grand Arc Leeda 1. For the Publishers Symbol Books . Amberton Place. Leeds. 8. A Guide To The Purchase of Ready Made Hi-Fi Equipment. This book is sold subject to the Conditions that it shall not by way or trade be lent, re-sold hired out, or otherwise disposed of without the publisher', consent in any form or binding or cover other than that in which it is published. CONTENTS INTRODUCTION 2 CHAPTER ONE RUNNING IN GROOVE 3 CHAPTER TWO AMPLIFIERS 4 CHAPTER THREE LOUDSPEAKERS 12 CHAPTER FOUR TURNTABLES 16 CHAPTER FIVE PICKUPS AND CARTRIDGES 17 CHAPTER SIX RADIO TUNERS 20 CHAPTER SEVEN RAIDING THE PIGGY BANK 24 " - A Symphony Orchestra in One's Own Living Room." INTRODUCTION HIGH FIDELITY reproduction is the endeavour to obtain as faithful a likeness to the original sound whether it be music, speech or noises, as is possible with equipment available today. Years ago we called it Hi-Fi yet there have been improvements, and we hope these will continue towards the endless horizon we call perfection. High fidelity is not just an excuse to turn up the volume. Many a cynic has pointed an unconvinced finger saying. "Who wants a symphony orchestra in one's living room?" To explain this away: imagine an architect or ship designer who has just completed his figures for some ambitious venture. He does not build a life sized balsa wood model of the project but a scale model to show clearly what is intended. II is quite possible to build scale models and still show exactly the intricate details of the final plan. In the same way, even a symphony orchestra can sound realistic in one's living room, obviously at a fraction of its volume, providing the details are well reproduced. The constituent parts which enable such a reproduction to be possible are discussed in the following pages. But what basically is required, is that our equipment should have wide frequency response and large dynamic range, not adding to or taking away any part from the original, save its intensity. This book is not a "Poor Man's Guide to Hi-Fi " nor is it a catalogue for the comfortably off, there being plenty of these; (the documents not the people). We have omitted all mathematics, and technicalities are reduced to a minimum consistent with a lucid explanation of how and why. We deal with each section of a Hi-Fi system in turn, looking into the problem of what to consider and what to ignore, ending with a guide to purchasing your first Hi-Fi set -up. CHAPTER 1 RUNNING IN GROOVE At long last. the desire to possess Hi-Fi equipment by the general public is catching on. More and more people without any special knowledge now wish to play their records on something, which will reproduce a nearer approach to the original sound. For too long the possession of Hi-Fi equipment has been the passport into an esoteric society of those in the know. Although no class distinction entered into this, it did seem to the uninitiated that one had to know the dreaded password to become admitted. Firstly there is the technician or amateur constructor possibly being connected with radio or electronics knows the how and why. He built his own equipment years ago and has added to it bit by bit over the years. The very mention of 'sand filled baffle' or' Williamson' brings a nostalgic tear to his eye. The second character is the musician who knows what a piano should sound like; he can read the maker's name on the letter board when you play your prize recording. It is quite understandable for this man to demand faithful reproducing equipment. Finally there is the Hi-Fi snob, He reclines in his chair surrounded by the costliest of apparatus, a pair of stereo headphones about his ears, and the score of the ‘Eroica’ on his knee, When you call on him he switches to the speakers, turns up the wick and shatters the air with some way-out modern composition that even the composer can no longer understand. During conversation he casually bandies words about like: damping factor, bias compensation, decibels as well as musical gems like antiphonal and augmented fifth. With a determined expression, a well-tuned ear, and no intention to buy, the above people make their annual pilgrimage to the Mecca of Hi-Fi: The Audio Fair. From here one comes away with a dizzy head, aching feet, and no more idea of what one wants than prior to going. Perhaps the best plan is to make up your mind exactly what you want, how much you can afford to spend, and go and get it. Now comes the next snag. At the shop you will be confronted with either a "blind you with science" boff in or even worse, a "sell you it at all costs" salesman. Salesmen not only look alike but sound alike. Once you know their patter, you will not be influenced to spend your hard earned brass on their doubtful recommendations. When intending to buy Hi-Fi, go to a shop which specialises in this type of equipment, steering well clear of the all shiny and gold furniture stores and their like. Most of the reputable Hi-Fi dealers have on their staff a man, who, backed by a good knowledge of his stock, will endeavour only to sell you a good bargain. Unfortunately it is inevitable that he will come out with many baffling unfamiliar words; it is therefore the intention of this book to put you in the picture, so that you can confidently march to the Hi-Fi dealer, and know you have come away having being parted from your savings with apparatus which will be entirely satisfactory. Hi-Fi is a progressive disease and after a while you will be gripped with the need to improve things. This is quite normal and easy to do as the best Hi-Fi is made up of several discreet items, making it possible to improve on certain parts not considered up to it, without upsetting the rest. On no account be tempted either by a smart salesman or by your wife's enthusiasm to buy one of those shiny boxes we used to call radiograms. These are nearly always polished boxes of junk made up of a cheap auto-changer, a radio come amplifier, with tinny speakers fitted into the same cabinet as everything else. Even at over £100 they are still boxes of junk; for this outlay, you can buy a fairly reasonable Hi-Fi set-up. Many manufacturers are now offering packaged deals with worthwhile reductions if you buy the lot. Even having done this, should you not be completely happy, the weak link can be replaced by something better at a later date. Many people start by improving their speakers. We will take the individual units, which make up a complete system and examine their purpose one by one, explaining and exploding those dreadful words as we go. By the end of the book it is hoped you will feel a little more confident when you dig into your pockets and take the plunge. CHAPTER 2 AMPLIFIERS At one audio fair, the demonstrators of a well-known exhibitor were mystified by a man obviously wanting a stereo record player, but not wanting an amplifier. When the truth came out, this potential customer did not know that an amplifier was an integral part of a reproducing system thinking it was only to make things louder. To make this point clear, we will say here and now: an amplifier is the backbone of any reproducing system. Amplifiers come in all shapes and sizes, varying powers and performance specifications. The important thing is that the amplifier must be capable of handling any input of conventional form, must magnify the sound faithfully, without taking away or adding to it in any way. To measure this capability we usually specify the amplifiers' response over the whole audio (audible) spectrum from the lowest notes such as bass drum and organ pedal, to the tinkling triangle's upper register and their harmonics. Harmonics are the things, which give a particular instrument or voice its timbre. A violin and trumpet may both play middle A but sound quite different when doing so. The basic notes of the music are referred to as the fundamentals. Harmonics are multiples of the fundamentals and are generated by the musical instrument. An amplifier must therefore be capable of handling the harmonics also, and as these extend beyond the normal range of the human ear, the upper limit to the amplifier's range must also be beyond this. The audio spectrum therefore ranges from about twenty cycles per second, now known as Hertz or Hz, to about twenty thousand cycles per second or 20K.Hz. If an amplifier's specification exceeds these limits it is all to the good but must never be less. The amount the response of the amplifier falls short of this frequency range is measured in decibels or db. As 2db is the smallest change in sound the human ear can detect, the response of a good amplifier must be flat to within 2db from 20Hz to 20KHz. Many modern amplifiers do much better than this and quote a flat response plus or minus 0.5db from lower than 20Hz to over 30KHz. Some makers specify the - ldb points and some the - 3db points in an amplifier's response. This is the limit of the range where the amplifier's output falls off to 0.707of the flat rating. An amplifier's response is measured at about a quarter of the rated power. When measured at full power, the response is known as the power bandwidth and is frequently somewhat less than the normal quoted response specification. Power output has been a matter of controversy for a long time. The fact is that the average power being pushed out at moderate indoor listening levels is only about 200 milliwatts; So why do we need a ten watt amplifier? " . Although the average power is so low, although it may actually sound quite loud, there are peaks of sound now and then, which are considerably higher pushing the power up to several watts. Whilst these cannot be heard as such, if they were chopped off by an amplifier incapable of handling them, the sound as a whole would suffer. When this gets bad, the sound seems to be being forced through an old sock. H As you will know, all music is not played at a constant volume level but is made up of loud and soft passages. Sometimes a fairly quiet piece of music contains a sudden loud passage or just one short sharp chord or drum beat. Cymbals are a typical example of this. Now imagine (Image Missing) " _ Sounds Like A Box Of Nails. W such a piece of music being played on your amplifier; the output is about 100mW and nice and quiet then BANG! The loud part sends the power up to say two or three watts with peaks up to almost ten watts. Few people ever wind their amplifiers up to power levels of ten watts indoors (windows can be expensive) but the above explains the need for powers in this order. There are however many amplifiers and small record players around rated at about five watts which sound very good indeed but, when you switch to a bigger beast, at the same volume level, the sound is more full bodied. The present trend is to increase powers up to almost PA level; many recent models being in the order of twenty to thirty watts per channel. The Americans needless to say go in for 100 watt monsters in their traditional manner. A word here about the power rating of amplifiers. The standard British method is to quote RMS power into a stated load, usually 15 or 16 ohms. This is the maximum continuous root mean squared power the amplifier will handle. Don't panic about these long mathematics, only remember that RMS is the basic and most honest measurement of true power, and the one most electrical instruments are based on. The Americans rate their amplifiers in peak power. This is exactly twice the RMS power so the impressive sixty watt American amplifier is only a thirty watt British equivalent. The guitar playing pop fraternity use peak power as it sounds more impressive. With the advent of transistor amplifiers another method of power rating has come into use. The way in which most transistor amplifiers are designed, one can obtain greater powers for short durations such as occur in music than can be obtained continuously. A ten watt unit may be rated at fifteen watts music power. The short spikes of high power we spoke of earlier can be accommodated even more easily. Again the Americans jumped to this possibility and rated the music or short duration power or IHFM. These mystical letters mean The Institute of High Fidelity Manufacturers and their 15 watt IHFM amplifier could be our old ten watter. Stereo can now be thought of as standard practice and here another power rating can be overlooked. When considering a ten watt amplifier, make sure it gives ten watts per channel. There have been amplifiers offered boasting of their compact size for ten watts output. When investigated one finds the ratings are for both channels added together and music power or even peak power at that. This means we only really have a 2.5 watt amplifier, which most likely sounds like a box of nails". Whether you finally obtain an amplifier in the sixty watt class, enough to blow your cap off, or something a little more modest; it is suggested you consider ten watts per channel as being about right for normal domestic use. A larger animal will not add much to the quality at normal listening levels but will do no harm either. The choice then in this respect is up to you. DISTORTION We spoke earlier of harmonics and this brings us to the next problem. Whilst musical instruments can generate harmonics to their hearts delight, this is unforgivable in an amplifier. Any non-linearity in an amplifier will cause harmonics to be generated, and as these forma distortion of the original sound; the distortion in an amplifier is usually a measure of the percentage of harmonics being generated. (THO). A pure tone known as a sine wave is fed into an amplifier and the output examined for harmonics of this. Any distortion of the pure shape of the wave is in fact converting some of its energy into various harmonics. A good quality Hi-Fi amplifier should have a harmonic distortion figure of less than 0.5% the modem figure of 0.1% is aimed at and some rather expensive amplifiers actually claim as low as 0.03%. Just how much harmonic distortion has to be present before the human ear becomes aware has been argued over for some time. It has been said that the major broadcasting organisations don't bother adjusting their transmitters until over 5% distortion, therefore one can say as much as 1% or more has to be present before becoming noticeable, never mind objectionable. There is another form of distortion called intermodulation. This too is caused by non linearity and is the very root of modern radio where it is called mixing or heterodyning. Try whistling a steady note; get a fellow near by to whistle a note a little higher or lower in pitch and note the strange effect in your ears. Besides the two whistled tones, you will be able to detect a third lower noise groaning in the background. This unpleasant intruder is caused by the two notes beating together; it is arithmetically the difference between the frequencies you are both whistling. Any non linearity in an amplifier will cause this effect and as the beat note or heterodyne frequencies are not harmonically related to the original s. they sound more objectionable than does harmonic distortion. As intermodulation is harder to measure accurately than harmonic distortion it is rarely quoted. Generally speaking if an amplifier has very low harmonic distortion then the intermodulation will be well within acceptable limits al so. SENSITIVITY The term sensitivity gives a clue to its exact meaning. All the various inputs should be sufficiently sensitive that when fed with a normal signal the amplifier is driven to full power with the volume turned up to full. Perhaps here it is well to list the sensitivities one would expect from various possible inputs. Magnetic pickup 2-5 mV Radio tuner or Tape amplifier 80- 500 mV Ceramic pickup 35- 100 mV Microphone 3-10 mV Record/playback head of tape recorder 2-5 mV BASS AND TREBLE CONTROLS Separate bass and treble controls are provided on all Hi-Fi amplifiers to give a boost or a reduction at the ends of the audio spectrum. If the whole of a reproducing system were perfect these could be omitted but things being as they are; bass and treble controls are fitted to makeup for such imperfections as room acoustics speaker deficiencies, and your ears. A boost or cut of some 15 db at say 40Hz in the bass and 14KHz in the treble register is about normal. One seldom needs to wind up or down these controls to such limits but a record lacking in bass for example can be improved by advancing the bass control a little. Pieces of equipment with a knob which merely states ~ tone ~ should be avoided like the plague as even the lowliest Hi-Fi amplifier boasts separate bass and treble controls. VOLUME AND BALANCE The one control everyone is familiar with is the volume. Some amplifiers, especially Japanese and American have an extra control called loudness. This is a device for compensating against the non-linear relationship between volume and frequency of the human ear. At low levels the sensitivity of the ear to very low and very high-pitched sounds is not as great as at higher volumes. What the loudness control does is to put on a little treble and bass boost when the volume is turned down low. As the human ear and brain are most accommodating. it is considered by many a mere gimmick to incorporate a loudness control and very few of the British manufacturers fit one. Also as there are bass and treble controls already fitted, many feel there is little point in adding more. The balance control is a differential volume control which varies the level between the left and right hand channels. THE SELECTOR SWITCH This as its name implies switches in the desired input at the same time, applying the appropriate correction or equalisation to the response to produce the necessary characteristic. FILTERS Elaborate fillers appear to be a dying race. With the demise of the scratchy 78 RPM. Record the country wide coverage of VHF FM transmissions, the need for filters is much less these days. Earlier amplifiers had switch filters working at for example 15. 11. 8KHz and basically cut off fairly sharply all frequencies above these figures. The fancier makes provide a slope control also. This varies the steepness of the main filter making it more or less sharp. Modern amplifiers in the more expensive range frequently now only provide one fixed frequency HF filter at about 8KHz usually brought into operation by a push button. Low frequency or rumble filters are sometimes included in the more elaborate amplifiers. Occasionally a fixed filter at some very low frequency is permanently included into the circuit design or made switchable by a push button. Again with a good quality turntable, a rumble filter should not be necessary, but in some Iistening rooms, feedback can occur through the floor between loudspeaker and pickup, causing a honking or fog horn sound to build up. In these cases, a rumble filter can work wonders. Both HF and LF filters are desirable luxuries found in the more expensive amplifiers but are not essential to good reproduction. Many an excellent amplifier has neither type of filter. VALVE OR TRANSISTOR? Here the world is divided into two camps and for no good reason at all. The "dyed in the wool ~ old timer will swear by his big bottles and say without any real knowledge that transistors are no good at all. This is nothing but prejudice; some people even talking about the transistor sound. Early transistor amplifiers like earlier anything else had a few snags and of course a bad name sticks. Providing their ratings and overall specifications match, a valve amplifier and a transistor will compare in performance in every way. It is possible to design much fancier circuitry with transistors than was possible with valves, some of which should in theory outperform valve designs. In actual fact , there should be no audible difference between two comparable circuits. If you prefer valves, then stick to a valve amplifier; if you feel you must be "with it", your choice will be transistors. The only real advantage transistors have over valves, other than the various clever technical arguments you may come across, is the fact that a transistor amplifier burns less electricity and runs cooler than a comparable valve amplifier. CLASS A AND CLASS B At some time you will almost certainly meet up with this little source of argument. Without delving into the endless technical details, it might be a good idea to explain the meaning of these expressions so that you will not have the wool pulled over your eyes when you go to buy. All sensible amplifiers whether valve or transistor use basically two devices working in what is called push-pull in their output circuit. In other words two valves or two transistors share the work between them. With Class A design s, both devices burn a fairly high steady current. The signal then causes one to increase in current while the other decreases, after which they return to normal then reverse, the first decreasing its current whilst its mate increases, rather like a see saw. Whilst there are many variations on this theme, valve amplifiers which use an output transformer, have worked on this principle for years and still do. With Class B, neither device burns a large current when there is no sound. Only a very small current known as the quiescent current being burnt. When the signal is applied, one device whether valve or transistor goes into conduction quite heavily on one half cycle. It then returns to zero and the other device switches on to complete the other half cycle. So what is difficult about this? As we have said valve amplifiers always have to have an output transformer, a costly item in itself. As Class A output stage pairs perform equal but opposite movements, one going up as the other goes down; any common movement or things they should not do are cancelled out across the transformer. Unwanted signal s and many harmonics therefore never reach the loudspeaker. With Class B on the other hand. only one device is switched on at a time, therefore no such cancellation can occur. This is the first arrow the Class A enthusiasts throw at the Class B defenders. Next is that much loved expression: crossover distortion. You have probably heard of this already and been filled with doubt and misgivings. We stated that the output devices in a Class B circuit take it in turns to do their work; obviously one must switch on at exactly the instant the other switches off. Any overlap only burns extra current but a gap in the middle causes what is known as crossover distortion. This is most noticeable at low volumes and causes a gritty sound to the music. To overcome this, we apply a steady bias to the two output devices just sufficient to cause them to burn a little current (the quiescent current), so that the bottom bends are straightened out. What this means is that just as one half is switched off, the other is being switched on with no gap in the middle. The above two snags made Class B amplification with valves quite out of the question, although high power PA and transmitting equipment use this principle where great power was needed regardless of quality. With the advent of transistors heralding a new epoch in the world of electronics, circuits were devised where the output transformer so necessary with valves could be dispensed with. With one bogie out of the way, designers took another hard look at the Class B problem. In its favour was the fact that a large standing current causes transistors to heat up which they do not like, making the necessity of providing elaborate cooling systems. These are called heat sinks. In fact with few exceptions, the standard practice now in transistor Hi-Fi amplifiers is to use a transformerless Class B design. Class A disciples still mutter on about crossover distortion and lack of balance, pointing out that in their opinion a Class B circuit can never be as good as a Class A design. Facts are facts however, and there are now available numerous amplifiers which can deliver twenty watts with only 0.05% distortion using this principle. So at the risk of being attacked by engineers brandishing girt brute slide rules, we utter this profound statement: Class B Hi-Fi amplifiers are every bit as good 8S Class A types. We will however qualify this by adding; 'providing the man has set the quiescent current correctly'. INTEGRATED AMPLIFIERS This title means simply that the amplifier is complete within its box. Early amplifiers of any size were made in two halves. The main amp being a heavy piece of metal work was usually housed on a stout chassis or box and laid at the bottom of the equipment cabinet. The control unit or pre-amp being much lighter could be mounted on one's control panel more conveniently, the two being linked by a multi-cable. Transistor amplifiers having got rid of the heavy output transformers can be made light and compact enough to assemble the whole amplifier in one piece and mount it reasonably easily. Integrated amplifiers should not be confused with integrated circuits. These little wonders of the age are a fairly complex circuit, with all its components reduced in size down to microscopic proportions about the size of a pin head. About now these tiny creatures are starting to crawl into solid-state amplifier circuits. At the end of this chapter we have printed a typical specification of a Hi-Fi amplifier to illustrate the sort of things you might expect to come across. Apart from those already mentioned there are such words as "damping factor". This is the degree of control the amplifier has over a speaker. Any tendency for the speaker to overshoot, resonate or create some other spurious sound is damped out by the amplifier. A good amplifier will have a damping factor of over fifteen and some even as high as sixty. A figure of thirty is fairly typical of a good circuit; a good damping factor does wonders for a mediocre speaker unit. It has been suggested however that a damping factor greater than twenty five to thirty has an adverse effect on the performance of a first class high efficiency speaker. The actual effect is a reduction in bass and a tendency for the reproduction to be a little lifeless. Connected with this, and sometimes stated is the output resistance. This is the resistance of the amplifier as seen by the loudspeaker and is typically about 0.50hm in a modern unit. When using standard 150hm loudspeakers, the amplifier having an output resistance of 0.50hm, it is easy to see where the damping factor of thirty came from. NEGATIVE FEEDBACK This is usually stated in decibels. Briefly what happens is that a fraction of the amplified output of an amplifier is fed back to the input in such a way as to partly oppose the input signal. Whilst not being the cure-all fairy godmother many fondly believe, negative feedback or NFB does reduce to negligible proportions distortion generated within the amplifier. A poor quality input signal however only comes out as an amplified poor quality signal. Typical figures quoted in a good amplifier are in the order of 40 to 60 db NFB. It is this feedback which gives the amplifier a high damping factor, as that unwanted movement in the loudspeaker cone generates a signal. This is fed back to the input of the amplifier via the NFB loop, reamplified and an opposing signal is fed to the speakers preventing the original movement, Hence electrical damping. HUM AND NOISE Hum is self explanatory and noise generally means white noise most noticeable as hiss. A hiss can be tolerated at low levels but when it becomes loud is most objectionable. A figure of -75 to -80 db is very good indeed and in fact quite inaudible, MATCHING This is a much overrated pastime. You may ask: “Will this amplifier match my loudspeakers?" The short answer is yes. Any good modern amplifier will match or at least be able to drive any normal speaker. Speakers intended for Hi-Fi applications are usually in the order of 10 to 16 ohm impedence. Matching is one of those things we learn about early in radio and electronics but seldom grasp its true significance. Correct impedence matching ensures maximum transfer of energy between one circuit and the next. In many electrical circuits. matching is necessary because of efficiency, but the waveform may change its shape considerably in the process; only the energy remains the same. In Hi-Fi it is more important to preserve the shape of the waveform than to be efficient . hence it is normal good practice to drive a high impedence device from a low impedence source. You will recall we drove our 15 ohm loudspeaker from a 0.5 ohm amplifier, and you didn't grumble. SPECIFICATION OF HI-FI AMPLIFIER The following figures represent a fairly typical amplifier; they are not the ultimate in performance, neither are they the lowest permissible ratings. This would be a stereo amplifier giving ten watts per channel. RATED OUTPUT 10W per channel continuous RMS into 150hm. 15W music power into 15 ohms. 15W continuous RMS Into 8 ohms DISTORTION 0.2% THO at 10W output RESPONSE - 3db at 10Hz and 35KHz. SENSITIVITIES Mag pu 3.5mV Ceramic pu 35mV Radio 150mV Tape amp 400mV Mic 5mV R/P head 2mV at 7.5, IPS CCIR BASS + 17 - 15db at 40Hz TREBLE + 16 - 14db at 14KHz BALANCE + 3db to zero both channels. HUM AND NOISE - 80db 8t min volume. CROSS TALK - 60db 8\ 1KHz. NFB. 60db. DAMPING FACTOR 30 OUTPUT RES. 0.5 ohm. HF FILTER 8KHz push button, 12db/ octave. RUMBLE FILTER fixed at 20Hz. H You can expect to pay from about £26 to somewhere in the region of £100 for a good Hi-Fi amplifier. Compare the specifications as much of the cost may be in providing many of the extra facilities such as switched filters etc. CHAPTER THREE LOUDSPEAKERS The loudspeaker is perhaps the most important part" of a whole Hi-Fi system. It is from the speakers that the sound comes and no two different shapes ever sound alike. It might be a good idea to explain why a speaker cabinet or enclosure is necessary at all. The greatest number of speakers in use are of the cone type. These radiate sound from both the front and the back. Consider the sound emitted from the front of the cone. As the frequency or pitch is increased, the sound tends to come together into a beam; in fact at the extreme upper end, one has to align one's ear directly in front on axis in order to hear anything at al l. As the pitch is lowered into the bass region, the sound opens out and out until it diffuses in all directions equally well. If you imagine the cone pushing air forward at one instant compressing the air in front , it must also tend to cause a vacuum behind the cone. At low frequencies where the sound is not directed forward into a beam, the air in front just moves round to take the place of that removed from the rear and none gets radiated. To obtain good bass then, we must segregate the front from the rear. At one time it was very popular to fit a speaker into a large baffle or even into a hole in the wall between two rooms For good results the baffle has to be large, but without doubt, very clean bass could often be obtained. To overcome baffle resonance which can either absorb sound or produce a boom, the practice of filling a double thickness with sand was all the rage 50 years ago. The next approach is to fit the speaker into a box so that the rear is totally enclosed thus not allowing the two out of phase sounds come together. Total enclosures or pressurised cabinets as they are sometimes known, are usually the basis for those very small bookshelf loudspeakers - very popular recently. The inherent cone resonance or bass resonance as it is called sets the lower limit to which a speaker can be expected to operate satisfactorily! Unfortunately, when a speaker is fitted into a total enclosure, the bass resonance is pushed up due to the elasticity of the compressed air within. This means special methods of cone suspension are called for to produce an extra resonance. Rubber or neoprene sometimes called a roll surround is used to obtain this. There has been a public demand in recent years for smaller speakers and whilst many of these produce a surprisingly good quality sound with wide response; there is no doubt that in general, the bigger the better. Construct a speaker unit of a given size; well engineered it produces a given satisfactory sound. Now increase the dimensions by just one inch all round, and it sounds three inches better. Although as we have said, the little bookshelf speakers do very well for themselves. They do tend to seem a little lost in a modern through lounge. For a small room, eight inch or maybe ten inch units are recommended. In the larger room ten inch or twelve inch units come into their own. Some very good neat eight inch pressurised enclosures are available today and worth considering for the smaller domestic situation. The most traditional and perhaps well known of enclosure is the reflex or bass reflex as it is sometimes called. These are tuned cabinets. A hole or port and sometimes re-entrant tube is fitted into this more sizeable box, the whole thing behaving like a resonant drum or organ pipe. The resonant frequency is made very low to almost coincide with the bass resonance of the speaker cone. This has the effect of slightly lowering the cone resonance giving an extended bass range. Although these enclosures are somewhat larger than pressurised units, they certainly produce good powerful bass notes. For some idea of the sizes, an eight inch unit requires over one cubic foot, a ten inch over two cubic feet, and a twelve inch about four cubic feet. Perhaps the reason why the tiny speaker sounds rather unreal is the hole in the wall effect Imagine you are listening to an orchestra but rather than being in amongst them, you are in an adjoining room listening through a four inch hole in the wall. You would still be able to hear everything but the sound would be coloured by this unnatural listening method. With a bookshelf speaker, this same small source of sound seems to colour the otherwise excellent performance. As the size of the speaker is increased, its ab il ity to reproduce the higher frequencies decreases. To overcome this, a tweeter or high frequency speaker is added to fill in the fallen off region at the high end. Some loudspeakers have metal, or bakelised cone centres to improve the upper registers and their coils are wound with aluminium wire rather than copper to make them lighter. Nevertheless an added tweeter fed through a protection capacitor gives a brilliance to the reproduction which would otherwise be a little dead. A Trumpet Should Leap Out and Hit You. (Image Here) CHAPTER FIVE PICKUPS AND CARTRIDGES Your transcription motor may have a pickup or tone arm as it is sometimes called, fitted as part of the structure. On the other hand you may have to obtain one and mount it separately. Here again your watchword is transcription arm. The cost of these vary and you would be better advised to accept the recommendations of a reputable Hi-Fi dealer. The better class or arm have a knife edge or gimbal pivot system. A large counter weight is adjusted to give zero gravity then a smaller weight slid up a bar to create the recommended stylus pressure, or tracking force as it is more correctly described. Sometimes a mechanical lever or system of dangling weights are fitted incorporating the bias compensator. This frightening expression simply means a device to overcome the tendency for the pickup to pull into the centre of a record. A small weight or spring keeps the pickup riding on a steady course without tendency to pull inward or outward. One word of warning: some of these more elaborate pickups having so much assorted junk tied on, take up a lot of room. Make sure your equipment cabinet has room or it could be embarrassing to have to cut a great chunk of wood out of the back. At the end of the pickup arm is the shell, which is usually a plug -in device held home by a lock nut; into this fits the cartridge. Cartridges belong to two main families' the piezo-electric and the magnetic, ranging in price from 25/- to over £45. Modern piezo-electric types are normally ceramic; crystal types only being used on cheap one valve record players and radiograms etc. Ceramic cartridges give a sizeable output. a good one costing about 4 to 5 guineas. Until recently there was a large gap between these and the magnetic types, starting at about £12 to £15. A few imported magnetic cartridges are arriving here from the Far East and can be bought for under £4. Except for what might be called budget systems, where a ceramic cartridge will do a good job, the seeker of Hi-Fi should invest in a magnetic cartridge. For such a tiny device, a whole se lection of long words and scientific jargon has crept in to unnerve the would-be buyer. All that happens basically is that the movements applied to the stylus by the grooves of the record cause 8 form of dynamo to generate electrical impulses, which are then fed to the amplifier. What could be simpler? - but not a bit of it. There is a whole branch of mechanics involved in simply coupling the stylus point movements mechanically to the electrical parts within. Rather than involve you in this mass of clever stuff, we will pick out a few of the more noticeable words and explain them. OUTPUT The cartridge will deliver a given output when excited by a record groove of given modulation. Frequently sensitivity is quoted for example: 1mV per em/sec and sometimes the voltage output which can be expected from a normal LP record, for example: 3mV. Make sure your amplifier has a magnetic pickup sensitivity of between 2 and 5mV in order to amplify adequately, these figures being typical mean that almost all pickups can be accommodated. TIP MASS This refers to the inertia presented by the stylus tip and should be as low as possible in order to respond to the high frequency intricacies of a complicated musical passage. Often quoted is effective tip mass, which may be for example 1mg. COMPLIANCE This is the ability the stylus and lever system has to move with the impressions of the record groove; it is the opposite to stiffness and high compliance means a less rigid movement giving cleaner reproduction. Here the figures get a little technical and range from possibly 15 to 30x10 em/ dyne. A typical compliance figure would read 20 x l0 em/ dyne. Sometimes a compliance unit is used which represents the 1/10 em/dyne bit; thus the same cartridge would read cu- 20. Obviously the higher the better. RESPONSE In much the same way as amplifiers, the response will be quoted between two limits. For example: the response may be stated to be within plus or minus 2db between 20Hz and 20KHz. Many a so called good one will deviate further than any 2db from the zero line; obviously one looks for the flattest response over the widest frequency range. Cartridges whose response shows humps or dips should be avoided. Due to the mechanics of the lever system, the performance on programme can give different results in practice to that expected from the specification. Two cartridges might well give almost identical figures from a tone test record but sound a little different when confronted with Wagner or Mahler. Similarly a cartridge which displays a few doubtful looking humps and bumps may sound quite good on programme. An old hand in HiFi will have read the reviews on the various cartridges and made up his mind already, but the newcomer rather than have to read up reams of spiel, would be better advised to put his trust in the experiences of the man at the shop. SEPARATION This is the amount the two channels are affected by or rather unaffected by each other. It may be quoted as -25db at 1KHz or a more detailed analysis given like l on R -30db at 1KHz, R on L - 2Bdb, the same thing being repeated at different frequencies. Graphs are usually supplied showing both response and separation. The separation in db's should be as high as possible over the region from a few hundred cycles to about 12KHz. Recommended load is nearly always quoted and this usually is about 47K to 100K, which is normal to all modern amplifiers, therefore this can be ignored in most cases. Inductance is sometimes quoted but may be ignored as this mainly concerns amplifier designers who will have already taken care of all eventualities. Other words such as tracing distortion, tracking angle (usually 15°) and inner groove distortion will no doubt crop up during your investigations. All these shortcomings are designed out of the pickup arms and cartridges as far as possible by the manufacturers. When installing a pickup arm and fitting the cartridge, read carefully the instructions for setting up, balancing, and tracking force. A cardboard template is usually supplied to ensure the pickup is mounted with the correct overhang, arc and height to give specified results. A recent Americanism to appear is "trackability" which rather explains itself. Many cartridges now are offered with a choice of tip, either conical which is the traditional form, or elliptical. With an elliptical stylus, the tip of the diamond is ground with a small radius, 0.0003" at the side edges which contact the groove wall and a larger radius 0.0008" front and back. Needless to say these are more expensive than the ordinary conically ground type but the improvement in the way they handle the difficult passages has to be heard to be believed. As many composers finish their works off with a good blast, it frequently occurs that this most demanding part of the music coincides with the last half inch of recorded grooves on an LP where the tracing distortion is likely to be at its worst due to the steeper angle the pickup makes with the plain of the groove. The elliptical stylus is designed to overcome this problem which is noticeable more with the conical type. On Your Old S team Radio ," (Image Here) CHAPTER 6 RADIO TUNERS Almost everyone is familiar with AM steam radio on medium and long waves. Except for those listening in fringe areas or where Continental interference is permanently noticeable, the various shortcomings of this form of radio broadcasting were not appreciated by many until FM broadcasting at VHF was introduced. To publicise the benefits of VHF reception, much has been made of its interference free properties but not enough it seems of its improved audio quality, The MW stations by international agreement are spaced at about 9KHz intervals with a good few unofficial stat ions jammed in between which greatly restricts the available bandwidth; this means the transmission's audio spectrum is very low giving the somewhat muffled quality which is characteristic of AM broadcast radio. There is no technical reason why at very high frequencies (VHF), where there is a little more radio space to play with, the quality of AM transmission should not be every bit as high as FM. The reason FM or frequency modulation is chosen is because it is a simpler matter to build ignition and similar electrical interference preventing circuitry into the design of receivers. When FM was first introduced, ordinary broadcast receivers had VHF facilities added as an extra, many not seeming to benefit by the potential advantages of this mode of reception. The inclusion of VHF then became standard practice in domestic radio designs although many listeners did not seem to appreciate the benefits. To many, Hi-Fi means primarily the reproduction of discs, a radio tuner being a desirable extra. In practice one does not play records endlessly and the Hi-Fi system becomes the normal domestic radio receiver in the home when a tuner is fitted. Tuner units or radio feeders as they have sometimes been iII named,· have been around for some time. The improved quality of FM made a VHF tuner first choice with the Hi-Fi enthusiast but quite a number include AM also on MW and in some ambitious units, long, medium and short. As you will see, the tables have turned; VHF being the primary object with AM playing second fiddle, for those (usually the lady of the house) wishing to receive the pop programmes during the daytime. Local radio and stereo broadcasting have now made VHF more popular with the general public and the improved performance of FM has made many a little more Hi-Fi conscious. There are many and varied FM tuners available today, with a bewildering range in prices luckily many of the inexpensive tuners, unlike other pieces of Hi-Fi hardware, are realty quite good in general performance. There are tuners especially from the American stables, which cost a bomb due to the complexity of their electronics within. It will be a long time before it becomes common for listeners in British cities to have to sort out over twenty local broadcast stations, crammed into the relatively narrow band as is found in parts of the USA. In order to separate out these many stations, some of which transmit stereo making matters more difficult, these elaborate receivers have been developed. The more reasonably priced tuners still offer a range of advantages and disadvantages, which we will try to guide you through. Normal coverage for an FM tuner is from 87MHz to 108MHz, although the official VHF broadcast band covers only 88 to l00MHz, there being little over 95MHz. The very cheapest tuners only employ broadband tuned circuits in their aerial coupling and RF stage which can in some cases lead to unwanted breakthrough of stations not actually in the FM broadcast band (See Selectivity later). Try to find out whether a tuner has a fully tuned RF stage. Many facts and figures may be given, some not exactly relevant to the users' needs: we ~- A Simple Dipole· (Image appears Here) will examine these later and explain their meanings as we have done with amplifiers and pickups. Some have a tuning indicator or meter which is very helpful in zeroing dead on station, essential for good reproduction. This can be omitted with safety in many modern tuners which employ AFC or automatic frequency control. AFC tends to make tuning easier and holds the tuner on station once tuned, any tendency to drift being checked. AFC therefore is very desirable and can be found on many of the better inexpensive tuners and is standard on the more elaborate ones. Sometimes by operating a small switch, tuning can be either manual or auto. The station is tuned in manually using a tuning meter to get dead on the station; the AFC is then switched in, when the tuner will lock on to the station remaining accurately in tune, the meter being now disconnected. Tuner amplifiers are popular now and combine a tuner, sometimes multi-band, with a complete Hi-Fi amplifier. These are convenient as everything is in one box eliminating connecting wires, and one less mains flex. The great disadvantage is that if some part of the tuner-amp is not exactly satisfactory in some way you are stuck with it, whereas with a Hi-Fi system made up of individual pieces, you can change the tuner or amplifier if one is not quite suitable to your needs. Also when examining different models with a view to buying, there is much more to take into consideration with a tuner amplifier. "Surely," you may now say, "is not a tuner amplifier the same as a radiogram?" You will recall we had some hard things to say about these in our opening chapter. The term tuner amplifier has been given to indicate that some attempt has been made to create something better than a radiogram. Of course tuner-amps vary considerably and you should look for exactly the same specifications as you would in individual amplifiers and tuners. FM tuners as well as tuner amplifiers now fit either as standard or as an optional extra a stereo multiplex decoder. Large areas of Great Britain are now able to receive the stereo transmissions radiated by BBC radio 3. As the transmissions are fully compatible, an ordinary tuner will give a mono output during a stereo transmission. To separate out the left hand and right hand channels, a stereo multiplex decoder is necessary. When buying a tuner, ask if the decoder is fitted and if not, try to determine whether this can easily be done if desired later. British tuners nearly always have a standard 75 ohm coaxial aerial entry and sometimes a 300 ohm balanced feeder terminal also. Many foreign tuners only have the 300 ohm aerial socket which is not very convenient for normal aerial systems. As with television, aerials are easily designed and constructed with a 75-80 ohm unbalanced coaxial cab le feeder. Many are surprised and in some cases put off by the fact that an aerial has to be erected. Pointing out that their old 1930 steam radio still goes with a bit of wire stuck into the aerial socket and an earth connected to the water pipe and their portable transistor set has no visible aerial at all they ask shy this new modern FM set requires such things as aerials. The answer is that frequency modulation is phase sensitive and being at VHF where reflections are liable to occur, some means of directivity is sometimes cal led for. A simple dipole is very effective in good service areas and can be made by cutting a 60" length of wire, tube or rod at the centre and connecting the inner and outer of the coaxial feeder to the gap. The aerial is then supported horizontally facing broadside to the transmitter. In bad reception areas a more elaborate aerial is required and may have to be fixed to the chimney along with the TV aerial. Those who experience multipath interference or reflections on their TV (ghosting) will appreciate the need for a good TV aerial. In the same way, ghosting affects VHF FM reception, resulting in a mushy and gritty sound to every transmission. When only mild, the effect is as if your tweeter cones have gone off centre, or some evil so and so, has thrown iron filings and sand into your speakers. When bad it is just a nasty noise and cannot be listened to. When this happens the only way out is a multi-element aerial high up. Sorry, your piece of wire will just not do unless you are in a very favourable position well inside the service area. Stereo multiplex reception is even more demanding and many an aerial has to be improved when a decoder is added to an existing tuner. In some FM tuners fitted with a multiplex decoder, a stereo beacon or indicator is provided. When a stereo programme is being transmitted, an indicator bulb lights up. This is not an essential in a good tuner, but a little luxury, which you may wish to have. Against programmes to be transmitted in stereo, a small letter s is printed in the "Radio Times It should be pointed out to potential listeners to stereo radio transmissions, that the stereo heard is a little more subtle than some of the gimmicky LP records we are accustomed to. Vivid directional effects are almost absent. but stereo does give an improved depth to the music which after all is what stereo is all about. Gone are the ping-pong balls and railway trains but one does hear the positioning of actors during a play. SENSITIVITY A high sensitivity whilst seeming a desirable aspect of a specification is not an end in itself. Unless coupled with a good signal to noise ratio and adequate front-end selectivity, which is rarely stated, a high sensitivity could well be a disadvantage. Where a lot of facts and figures are given regarding the above items, you may rest assured quite a lot of thought has gone into the design. However many makers do not quote the sensitivity figure of a tuner but this does not necessarily mean they dare not. To illustrate, imagine two conditions where a sensitive receiver can produce a given output when fed by a doubtful aerial, and a less sensitive receiver connected to a good aerial giving a similar output. You might at first think that one is as good as the other, but in fact, the better quality would result from the poorer receiver. A good aerial is considerably better than a hot receiver if a choice had to be made. SELECTIVITY Rarely quoted, this is the ability the receiver has to separate one station from the next adjacent. In communication receivers, selectivity is almost number one priority in design but in Hi-Fi FM receivers, where the bandwidth has to be wide to accommodate reception of stereo, selectivity takes a back seat. However selectivity is often quoted in terms of bandwidth at -3db, 300KHz being normal. In order to accommodate stereo transmissions, wider rather than narrower bandwidths are necessary and figures which were previously less than 250KHz are now raised as high as 350KHz. Front end selectivity is more important and is determined by the way in which the radio frequency amplifier at the front of the tuner unit is tuned. A good tuner has ganged variable tuning over the entire range which helps to minimise such things as cross-modulation and images, where signals like TV sound is received along with the wanted station. This is noticeable in fringe reception areas and where two service areas overlap. These facts are not always stated by manufacturers and the ones which do are to be encouraged. NOISE Noise in itself is not quite as important as signal to noise ratio; the highest quoted figure being the best. Sometimes only the front-end noise factor is quoted such as 4db, which is quite good. Inter-station noise cancellation devices are sometimes included or the word squelch may be found. These circuits cut off the sound whilst tuning between stat ions so the somewhat annoying hissing is not heard. Other tuners are far less noisy anyway, and do not have to have special squelch circuits added. Whilst on the subject of noise we might include interference suppression, the name limiter cropping up on some literature. As electrical interference and ignition noise can be considered as amplitude peaks, some sets have limiters which cut off these amplitude changes; the ratio detector most commonly used today is self limiting. OTHER FRIGHTENING FIGURES Some manufacturers assuming everyone is technically minded give many more figures and all quote the IF as 10.7MHz. This seems to be a worldwide standard and matters little to the buyer at all. IF rejection should be a fairly high figure as this indicates whether you are likely to hear strange short wave noises creeping in, a figure of 85db may be seen. Image rejection could have been dealt with under the heading of selectivity and is concerned with how well the early stages of the tuner are aligned or tuned. A figure of 5060db may be quoted. MULTIPLEXER We discussed the stereo multiplex decoder earlier but its inclusion gives rise to more facts and figures. The major item here is of course cross-talk; figures given may state: greater than 30db, the higher the better. Other figures are not important to the listener, but it is a good idea to choose the one which switches automatically between mono and stereo with the appropriate transmission being received. A stereo beacon or indicator may be included, and whilst being a pleasant addition is not essential. It is hardly our place to give an opinion on appearance, this being the buyers' decision, suffice it to say, a good clear scale and pointer of clean styling is both useful and aesthetically pleasing. *Feeder is the name given to an aerial downlead, whether eoaxial. balanced. or a single wire RAIDING THE PIGGY BANK It is hoped at this point, some of the apprehension has been taken out of your mind and your long repressed desire to possess a Hi-Fi system of your own is rekindled. Only you know how much you can afford. If this is no bother, then a first disappointment can easily be corrected by a better choice later. If you are like most of us and have carefully saved up all your pennies, and done the wife out of one weeks holiday this year; it is important your first choice is a good one. All is not lost if you do make a poor choice with your first faltering steps into this unknown. As stated at the beginning, HiFi being made up of a number of discreet items, the weak I ink can always be strengthened at a later date when the bank balance looks healthier. Again depending upon how much you are prepared or able to part with, is whether you buy a complete range of equipment at one go, perhaps as one of the attractive package deals, or only some of the items. It is suggested that a good amplifier is chosen from the word go, as this forms the corner stone of the whole system. Powers from eight to twenty watts RMS per channel are recommended making sure your choice can accommodate all eventual inputs you are likely to desire. Whether you choose a free standing model to blend into the decor, or one which will fit into an equipment cabinet; make sure no ventilation holes or louvres become blocked by not allowing sufficient space above. below and at the sides. 80th valve and transistor amplifiers require a passage of air to keep working temperatures down. Make sure you are familiar with your local AC mains voltage and set the tapping appropriately reading maker's instructions before putting into service. The next most solid building block to be obtained is the transcription motor. As stated earlier there are not many bad examples of these provided you insist on the fact that what you are offered is a transcription machine. You will be required to make a cut-out in your motor board to drop the turntable unit into; a paper template being provided for you to follow. Should you decide not to obtain a turntable and pickup arm combined, make sure there is plenty of room left on the motor board inside your equipment cabinet to house a separate arm. Not mentioned earlier is the fact that many of the better arms whether the super slim type or those displaying a cluster of dangling appendages, have a hydraulic lowering device to enable those with none too delicate a touch to avoid an ~ oops across their record surface. k Some turntables and pickups have a separate earth wire apart from the signal leads, which must be connected to the amplifier. Where the amplifier has no special earth terminal provided; this earth lead, which usually has, a spade clip fitted should be attached to the metal chassis close to the input sockets. Often a chassis screw can conveniently be loosened for this purpose. When installing the pickup arm, use the mounting template provided carefully following the makers instructions regarding position, height etc. as these are very important. Pickup cartridges and loudspeakers seem to be the most variable items and people tend to swop and change somewhat. A magnetic cartridge is strongly recommended rather than start with the cheaper ceramic type. Choose the one with the flattest frequency response, greater separation figure and highest compliance unit your pocket will allow. Cartridges are supplied with a selection of hardware to facilitate easy fixture to any modern shell. Observe the recommended tracking force (weight), by adjusting the arm as per the instructions given with the arm. Where the turntable comes complete with pickup and cartridge, a moderately sized booklet is often provided to keep you engrossed for hours. Complete turntable units are available mounted on plinths where all the donkey work has been done for you by someone else. These are useful where you prefer a free standing amplifier and are able to house the whole system in a mexlarn room divider or shelf structure. Spread about Hi-Fi systems are all the rage just now but suffer the disadvantage of displaying miles of unsightly interconnecting wiring. When it comes to buying the loudspeakers gentlemen, you are on your own, Of should be. Whatever other desirable attributes the fair sex have to offer, the dear creatures simply are not wired for sound. Only about 2% of women readily appreciated the benefits of Hi-Fi. Whilst buying the amplifier and other apparatus, opposition to half this unnecessary expense will almost certainly have been experienced; nothing short of Machiavellian subterfuge will be necessary when planning to spirit in those great speaker enclosures. Bachelors with an ambition to eventually take the plunge will be well advised to plunge into Hi-Fi first, especially the speakers. Married men: send the little lady to mother for the day when a visit is planned to the Hi-Fi shop, for when she sees what you have brought home, she will certainly go there. To show that indeed many a true word is spoken in jest; many husbands visiting the Audio Fair with their wives were seen to be nagged at when showing interest in the larger speaker enclosures. Even during comparison tests where some little box was shown to be inferior to the more ambitious one, wives were insisting the little ones would do. Perhaps another book should be 'Mitten aimed at instructing the ladies what to listen for so that their cloth ears may grow into well tuned ones. Of course we do not suggest that everyone should install vast speaker enclosures but relate their size to their surroundings. For the smaller domestic living room a pair of eight inch enclosures are recommended and maybe ten inch units can be squeezed in. larger rooms will require a ten inch or perhaps a pair of ·twelve inch pressurised enclosures. For an idea of size, the eight inch units will be between one and two cubic feet in capacity; the ten inch just over two cubic feet and the twelve inch from two to four cubic feet depending upon whether pressurised or tuned reflex cabinets are used. With the spacious modern through lounge, the tuned twelve inch units come into their own; even the giant three speaker systems would not be incongruous. These are only bare suggestions, there being so many varied designs and shapes all with their own unique tonal colouring that here we can do no better than reiterate what we said in the chapter on speakers. Go to a good Hi-Fi specialist and listen to as many speakers as possible. Pick out a number of enclosures about the size and shape suitable to your room and furnishings ask to listen to them all. Let your ears be the judge after finding out the facts and figures about the various types. What you should be listening for is range and depth of tone, lack of colouration, and general brilliance in the reproduction. A good plan before descending upon the Hi-Fi shop, is the night before to visit a live concert or theatre, or even a dance, to tune your ears to what the real thing sounds like. An astonishing fact is that many people have never heard a real piano, only what they believe a piano sounds like due to what they have heard on AM radio and record players. For this reason when a proud Hi-Fi enthusiast demonstrates his new array of equipment, the remark so often heard, especially from the ladies is, "Doesn't it sound tinny" For those who subscribe to the ~ do it yourself" cult, the loudspeaker enclosure has long been a centre of devotion. It is beyond the scope of this book to delve into the ins and outs of enclosure design, but a number of books are available on this very subject, aimed at the amateur who is able to combine his Hi-Fi with woodwork. The series of books by Mr. G.A. Briggs are both instructive and interesting, being aimed at those who demand the best in reproduction and are prepared to build their own. At about half the price, it is possible to build speaker enclosures to your own individual taste, with excellent performance in a way which would be Quite uneconomical commercially. You do not pay for your own man-hours, only the materials. Choosing a good loudspeaker to fit into your box requires a little care. The size of the magnet is the greatest clue to performance. Flux densities of 14000 to 17000 lines are common in Hi-Fi speakers. The cone suspension or surround is often rubber, foam plastic, or felt rather than the ordinary corrugated paper found in cheaper speakers. For a unit you can expect to pay between £5 and £10; for a ten inch unit, £6 to £13 and a 12" speaker £12 to £20. Tweeters, always a worthwhile addition, range in price from about 20/to upwards of £20. The coupling capacitor for the tweeter will only cost a few shillings from a radio dealer. Having now obtained amplifier, turntable and speakers you possess the basis of a Hi-Fi system. Placing the equipment and speakers in your living or listening room will depend much on the available space but it is suggested the speakers are placed remote from the turntable to prevent acoustic feedback. The left and right hand speakers should be spaced sufficiently wide apart to obtain the benefit from stereo but not for instance at each end of a through lounge where things would sound a little disjointed. For notes on phasing, see end of Chapter 3.The ideal listening position for stereo is at the apex of a triangle formed between yourself and the two speakers. Not many people now fix themselves rigidly in this position but feel free to move about the room and still enjoy the music. The added depth, which stereo gives is still noticeable when not in the ideal spot. There is nothing over complicated in installing a radio tuner, most people being familiar with tuning etc. One point however is that if no tuning indicator or meter is provided on an FM receiver, one should tune for the clearest reproduction which is not necessarily the loudest point, as in AM radio. You will soon know if a more elaborate aerial is required as the reproduction will be quite horrible. A quick clue if in doubt is to look through the window at what your neighbours have installed for their TV. If every house resembles a battleship, then very likely FM reception will be almost as troublesome as TV. In fair reception areas, a simple dipole will be sufficient and may be made as described earlier, preferably fixed high up such as in an attic or loft. The one item so far not mentioned at all is the tape recorder. Tape recording is a subject alone and whilst many a Hi-Fi devotee would fee l naked without tape facilities, many tape recording followers in clubs and as individuals care little for ultimate quality; the subject matter being the more important. Recording with tape is a demanding subject technically and until recently has not caught on with the Hi-Fi fraternity to the extent first imagined. Tape recorders comparable in price with the remainder of Hi-Fi equipment fall short in both dynamic and frequency range and in particular signal to noise ratio. Obviously it is possible to make recorders, which compare in performance with disc but these are very expensive. As almost predictable, the Japanese are producing some very respectable recorders at more attractive prices; stereo being the norm. The only guide here being that the quality is almost proportional to the price and in some cases the size. Live tape recording again seems the object in the recording clubs rather than in the home Hi-Fi. Gatherers of folk music, bird song, and other alfresco activities use small portable machines where again the subject is more important than the quality. Of course a good microphone can be very expensive. Very fair recordings can be obtained from small ribbon microphones in the £12 plus range, but when you consider a studio microphone costs twice what you are likely to pay for your complete Hi-Fi set up, the limitations are clear. The slow rise in popularity of Hi-Fi among the general population is sometimes blamed on lack of interest alone, the fact that many are unconvinced after listening to something good yet remain quite content with their old steam radio and scratchy gramophone. Another possible reason is lack of advertising. Hi-Fi is well advertised in the radio and Hi-Fi periodicals but only people interested in radio or electronics technically see the radio magazines and most of the readers of the Hi-Fi journals are people who already possess HiFi of some kind. One seldom sees Hi-Fi advertised in the popular press, yet motor cars, colour TV, cameras and clothing etc. get plenty of advertising space. If it were not for the window displays of retailers and of course the orgy of Hi-Fi : "The Audio Fair Hi-Fi would be relatively unknown. Now you are interested and eager to invade the Hi-Fi shop, may we ask you to look after your LP records; after all they cost plenty. The purchase of one of the proprietary disc cleansing devices is recommended and should be used before every playing. Keep the stylus free from dust build up. Users of transistor amplifiers are warned never at any time allow the speaker lines to become short circuited, as this is catastrophic. The author hopes his scribblings have helped at least some over the wall, and wishes you good luck, good buying and may you enjoy your music as much as your Hi-Fi.