Tascam M-35 Operating Manual 电路图.pdf

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1、TASCAM TEAC Production Products Audio Mixer OPERATION /MAINTENANCE RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 INTRODUCTION T 0 THE MODEL 35 The Model 35 is an audio mixing console design- ed to satisfy the requirements of modern multi- channel recording. Many of the auxiliary mixing systems nee

2、ded are built-in and can be re-routed to do more than one job. Fast, convenient and complete operation with 4- or 8-track recorders can usually be accomplished without re-patching. However, the process of multichannel recording is constantly changing, growing more complex as an art with each advance

3、 in technology. Your signal processing needs may require a unique arrangement of subsystems. No console has ever been built so large and complete in its routing that it could solve every imaginable problem with one button. Someone will always be able to come up with that unusual situation requiring

4、just one more mix. In order to copewith thesep unpredictable requirements, patch points are provided throughout al1 signal pathways on the M -35. As our mixing console becomes more flexible, the amount of time needed to understand the available function increases as well. The main signal path from m

5、ic in to line out is still fairly straightforward. The requirements have not changed much since the days of mono, but the routing for effects sends, cue feeds, and stereo monitoring can be hard to visualize. rhe beginner often overlooks the significance of connections that would be immediately obvio

6、us to the expe- rienced recording engineer. If you expect to find that extra rnix quickly, you must be prepared to study the layout of the M -35 thoroughly. Input module layout including back panel In most instances, the physical arrangement of As an example, if the controls on an input mod- the con

7、trols on the top pane1 has very little to ule actually followed the order in which they are do with the sequence of electronic parts inside. wired, the module top pane1 would look Iikethis. The actual wiring order is the information you Well put the jacks on the top, as well as the need to understan

8、d to use the M -35 successfully switches and faders. RadioFans.CN 收音机爱 好者资料库 While this arrangernent of controls rnight help the can be used successfully. So along with the docu- beginner to understand the flow of signal in the rnentation you will need for service (schernatic rnodule, it would be ve

9、ry inconvenient to oper- diagrarns, rnother-board layouts and rnechanical ate. StiII, the wiring sequence rnust be understood disassernbly inforarntion), we include asirnplified before the more cornplex functions of the M-35P electrical sequence chart called a block diagrarn. 16 15 17 Direct ml - P

10、9 solo This drawing shows al1 the controls, switches, arnplifying stages and connectors in their proper order. Learning to read it will provide theanswers to any questions about what cornes where on the inside. Even though the block diagrarn can indi- cate what is available in the way of extra circu

11、it flexibility, it cant explain why a connection or switch has been included, or suggest a standard layout. In the following sections of this rnanual, we will do our best to describe the individua1 functions and controls of the M-35, and how they can be arranged in more than one sequence; but, your

12、rnixing needs rnay be best served by an ar- rangernent of inputs and sub-systern connections you work out for yourself. To begin, well start with some basic inforrnation about sound and the nurnbering systerns used to describe levels in and out of the equiprnent and impedance-what the terrn rneans a

13、nd how to dea1 with the details when you rnust connect frorn our gear to other equiprnent. Many aspects will be discussed in the rnost basic language we can use. There is a vast arnount of inforrnation available to the beginning sound rnixer but rnuch of it is not basic enough to be easily understoo

14、d, or it assurnes that the reader has an engineering or scientific background and wil l be interested in the rnath. Practical rules of thurnb for the novice are not generally available. Sornething be-7 14 - from subrnaster T a e inn* tween a picture of the outside of the unit and a complete rnathern

15、atical analysis of the circuits inside is needed. You dont have to build a mixer frorn scratch, you just need to know how to operate one. However, some nurnbers are unavoidable. The M-35 rnixer does nothing useful without being connected to quite a lot of sophisticated gear. Mics, tape recorders, po

16、wer amps, and loud- speakers al1 play a part in the process of rnixingl recording and each piece of gear has its own re- quirernents and problerns. We have tried to rnake this rnanual as sirnple as technology will allow. Each section or topic will give you some basic instruction in the terrninology

17、used in the pro- cess of rnixing as well as a list of what plug goes into which jack. Whenever possible, the scientific terrns have been related to understandable cornrnon references. Understanding what isgoing on inside your equip- rnent will help you irnprove your sound. Think of this rnanual as a

18、 reference book. You wont need al1 of what is here to begin, and it certainly is not necessary to rnernorize it, but do try to find tirne to read it carefully at least once. That way you will be farniliar with its contents. If you need the nurnbers, they will be there waiting. Good luck with your so

19、und. THE DB; WHO, WHAT, WHY No matter what happens to the signal while it is being processed, it will eventually be heard once again by a human ear. So the process of convert- ing a sound to an electrical quantity and back to sound again must follow the logic of human hear- ing. The first group of s

20、cientists and engineers to dea1 with the problems of understanding how the ear works were telephone company researchers, and the results of their investigations form the foun- dation of al1 the measurement systems we use in audio today. The folks at Bell Laboratories get the credit for finding out h

21、ow we judge sound power, how quiet a sound an average person can hear, and almost al1 of the many other details about sound you must know before you can work with it successfully. From this basic research, Bell Labs developed a system of units that could be applied to al1 phases of the system. Sound

22、 traveling on wires as elec- trical energy, sound on tape as magnetic energy, sound in air; anyplace that sound is, or has been stored as energy until some future time when it will again be sound, can be described by using the human ear-related system of numbers called bels in honor of Alexander Gra

23、ham Bell, the inventor of the telephone. What is a bel and what does it stand for? It means, very simply, twice as loud to the human ear. Twice as loud as what? An obviousquestion. The bel is always a comparison between two things. No matter what system of units of meas- ure you are working with a t

24、 the time, you must always state a value as a reference before you can compare another value to it by using bels, volts, dynes, webers - it doesnt matter, a bel, or ear- related statement of twice as loud is always a ratio, not an absolute number. Unless a zero, or no difference point is placed some

25、where, no comparison is possible. There are many positive and definite statements of reference in use today. But before we go over them, we should divide the bel into smaller units. Twice as loud will be a little crude to be used al1 the time. How about one tenth of a bel? Okay, the decibel it is, a

26、nd O means no differ- ente, same as the reference. It seldom means nothing. Now, if you double the power, is that twice as loud? No, it is only 3dB more sound. If you double an electrical voltage, is it twice as loud? No, it is only 6dB more sound. The unit quantities must follow nonlinear progressi

27、ons to satisfy the ears demand. Remember, decibels follow the ears. All other quantities of measure must be increased in what- ever units necessary to satisfy the human require- ments, and may not be easy to visualize. Sound in air, our beginning reference, is the least sound the human ear (young me

28、n) can detect a t 1000 to 4000Hz. Bell Labs measured this value to be .O002 microbar, so we say OdB = .O002 microbars and work our way up from the bottom, or no perceivable sound to humans point. Here is a chart of sounds and their ratings in dB, using .O002 microbar pressure change in air as our re

29、- ference for OdB. 10,000 22 nch bass drum mic inride drum p n a r e druni l inch t 1 4 0 1 I p o w r ? I l c voice a t 1 inch Ircream) 10 newtoiir per 100 dvner per 100 100 -1 newton per 1 dyne per rquare rneter square cm. l niicrobar Auerage converratlun - - - . Home in citv, cantinuour background

30、 I microbar 1 : noire*(carr, rubwavr. rtreet nolre) - - - - - - - t Homen citv at night .O1 microbar Isoiared recording or TV studio Open field, night, no wind -001 microbar icricketr. nrect noirer, etc.) We should also make a point of mentioning that the maximum number on this chart represents peak

31、 power and not average power. The rea- son? Consider if even some monetary part of your recording is distorted, it will force a re-re- cording and it is wisest to be prepared for the highest values and pressure even if they only happen once in a while. On this point, statistics are not going to be u

32、seful, the average sound pressure is not the whole story. rhe words them- selves can be used as an example. Say the word statistics close to the mic while watching the meters and the peak LED level detector. Then say the word average. What you are likely to see are two good examples of the problems

33、en- countered in the real world of recording. rhe strong peaks in the s and t sounds will pro- bably cause the LEDs to flash long before the VU meter reads anywhere near zero while the vowel sounds that make up the word average will cause no such drastic action. To allow peaks to pass undistorted th

34、rough a chain of audio parts, the individua1 gain stages must al1 have a large reserve capability. If the av- erage is X than X + 20dB is usually safe for speech, but extremely percussive sounds may re- qui re as much as 90dB of reserve to insure good results. Woodblocks, castanets, latin percussion

35、 (guido, afuche) are good examples of this short term violence that will show a large difference between LED flash and actual meter movement. When you are dealing with this kind of sound, believe the LED, it is telling you the truth. Since the reference is assumed to be the lowest possible audible v

36、alue, dB spl is almost always positive, and correctly written should have a + sign in front of the number. But it is frequently omitted. Negative dB spl would indicate so low an energy value as to be of interest to a scientist try- ing to record one cricket at 1,000 yds. distance, and is of no signi

37、ficance to the multichannel recordist. Far more to the point is the question What is a microbar? It is a unit of measure- ment related to atmospheric pressure and al- though it is extremely small, it must be divided down quite a lot before it will indicate the mini- mum pressure change in air that w

38、e consider minimum audible sound. This will give you a better idea of the sensitivity of the human ear. One microbar of pressure change is slightly less than one millionth of an atmosphere, and you can find it on our chart as 74 dB spl. It is not terribly loud, but it is certainly not hard to hear.

39、As a matter of fact, it represents the average power of conversational speech a t 6 feet. This level is also used by the phone company to define norma1 earpiece volume on a standard telephone. Now think about that minimum audible threshold again: .O002 microbar. Thats two ten thousandths of a millio

40、nth part of one atmosphere ! This breakdown of one reference is not given just to amaze you, or even to provide a feel for the quantity of power that moderate levels of sound represent. Rather it is intended to explain the reason we are saddled with a ratiollogarithm measurement system for audio. Ad

41、ding and sub- tracting multi-digit numbers might be easy in this age of pocket calculators, but in the 1920s when the phone company began its research into sound and the human ear, a more easily handled system of numbers became an absolute necessity. Conveniente for the scientist and practical en- g

42、ineer, however, has left us with a system that requires a great dea1 of complex explanation be- fore you can read and correctly interpret a spec sheet for almost any piece of gear. Here are the formulae for unit increment, but they are necessary only for designers. And unless you build your own gear

43、, you wont have to dea1 with them. For power (watts) increase or loss, calculate by the following equation: 10 LOG, For voltage, current or pressure calculations: 20 LOG, v 2 v 1 = N (dB) One whole atmosphere, 14.70 pounds per square inch, equals 1.01325 bars. So one whole atmos- phere in microbars

44、comes out to be 1,013,250. Once we have this chart, we can see the differ- ente between the way humans perceive sound and the amount of force it takes to change air pressure. Unfortunately, the result is nota simple twice as much pressure of sound to be heard as twice as loud. If you plot decibels a

45、s the even divisions on a graph, the unit increase you need is a very funny curve. VOLTAGE, CURRENT / OF PRESSURE v1 dB = 20 iog, E wav 5 10 15 20 25 30 - increase R I S in even 1 dB Unit This is how the ear works, and we must adapt our system to it. We have no choice if we expect our loudspeaker to

46、 produce a sound that resembles the original sound we begin with. The high sensi- tivity to sound of the human ear produces a strong energy illusion that has confused listen- ers since early times. How powerful are the loud- est sounds of music in real power? Can sound be used as a source of energy

47、to do useful work, such as operating a car? For any normally loud sound the answer is, regrettably, no! Perhaps not so regrettably, consider what would happen if one pound of pressure was applied not to your head, but directly to your inner ear. One pound of air pressure variation is 170dB spl ! Thi

48、s a- mount of power might do some useful work - but not much, its still only one pound and to make use of it you will have to stand one mile away or you will go deaf immediately. If we reduce our sound power to realistic musical values, we will not be injured, but we will have almost nothing (in rea

49、l power terms) to run the mic with! This low available energy is the reason that high gain amplifiers are required for micro- p hones. When we take a microphone and pick up the sound, we do have some leeway in deciding how much energy we must have in order to operate the electrical part of our system. If wecan decide that we dont have to truly hear the signal while we are processing it from point to point and we can wait until the electronic devices have done L al1 their routing and switching before we need