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Rec.music.makers.bass Frequently Asked Questions (FAQ) part 2/2

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Archive-name: music/bass-faq/part2
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Last-modified: 1996/2/12

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                              REC.MUSIC.MAKERS.BASS
                         Frequently Asked Questions (FAQ)

			Part 2: Answers to Questions 12-21

   12. How are 5 and 6 string basses tuned? What are the advantages and
       disadvantages of them? How are 8 and 12 string basses tuned and
       what are their advantages and disadvantages?
       5 and 6 string basses have extra strings either above or below the
       normal 4 strings. On 5 string basses, the extra string is either
       tuned to B below the low E or to C above the high G. Rock and pop
       players tend to find the low B more useful, while jazz players and
       chord players tend to find the high C more useful. 6 string basses
       usually add both a low B and a high C although a few players add a
       high C and a high F above that. In the 60's a few makers (notably
       Danelectro and Fender) made basses that had 6 strings and were
       meant to be tuned E-A-D-G-B-E, same as a guitar but one octave
       lower. This idea never really caught on, and almost no one tunes a
       bass this way anymore.
       
       The advantage to the extra strings are that you can reach more
       notes in a given position, and can get some notes you could not
       otherwise play. The disadvantages are that the neck must be wider
       to accomodate the extra strings and that string sets are more
       expensive for 5-and-6 string basses.
       
       8 string basses are constructed similarly to 12 string guitars;
       the strings come in pairs, each pair containing a string tuned
       normally and another string tuned one octave higher. Both strings
       are plucked or picked simultaneously Most 12-string basses have
       the strings in triplets, one at the normal pitch and two tuned one
       octave higher, to get a fuller sound on the top note. There are
       also some 12 string basses which have 6 pairs of strings instead
       of four triplets. A 10 string bass could be constructed but no one
       has ever marketed one. There have even been a few 18 string basses
       constructed which had strings in triplets but these were built
       more to demonstrate the strength of graphite necks than for actual
       use.
       
       The advantage of 8 and 12 string basses is that because several
       strings are played simultaneously they have a richer, fuller sound
       that a regular bass. The disadvantages are that playing becomes
       much more difficult because both strings have to be fingered and
       plucked. In addition, strings for 8 and 12 string basses can be
       somewhat difficult to buy as very few companies make them and not
       many people buy them. Many manufacturers of such basses either
       sell strings directly or can tell you who supplies strings for
       their basses. If you are willing to order strings by mail this
       will usually get you what you need.
       
       
   13. Can I detune my 4-string to B-E-A-D?
       Re-tuning your 4-string to B-E-A-D can be very simple or it can be
       impossible. Usually all you have to do is replace the strings and
       modify the nut. However, some basses cannot accomodate a B string
       on the bridge end. Other than that, there should be no adverse
       effects (I have been using BEAD-tuning for two years now).
       
       
   14. What is the difference between a preamplifier and a power
       amplifier?
       Bass amplifiers, whether they are combo amps or stage rigs,
       contain three components: the preamplifer, power amplifier, and
       the speakers. The signal from your bass passes to the speakers in
       three stages, with an amplifier between each of the stages. The
       signal from your bass is carried at instrument level; floor
       pedals, which your bass plugs into directly, operate on the signal
       at this level. The instrument level signal is amplified to line
       level by the preamp. The line level signal is passed to
       rackmounted effects. Because the line level signal is more
       powerful than the instrument level one, rackmounts effects add
       less noise relative to the level of the signal than floor effects
       do, which is why professionals prefer them. Most preamps sold
       commercially also include a number of line level effects, though
       not all do. After the line level signal is processed it is passed
       to one or more power amplifiers. Most rigs use only one power amp
       but if you are biamping you would use two. The line level signal
       can also be sent to the PA system if your band uses one. The power
       amp amplifies the signal to the the much higher levels that are
       used to drive the speakers. The power power rating of a guitar or
       bass amp refers to the total wattage that is sent to the speakers
       by the power amplifier stage of the amp.
       
       You can buy a combination ample that contains a preamp, a power
       amp, and a speaker all in one box, or you can buy a separate
       preamp, power amp, and speaker cabinet. Professionals do the
       latter -- it's more expensive, and usually sounds better. It also
       gives you more flexibility to mix and match your components to a
       particular need. Many combination amps have a preamp-out jack,
       which allows you want to send the preamp stage's output somewhere
       other than the power amp. There are several reasons for doing
       that:
       
          + You could send the preamp out into a mixing board in addition
            to your power amp for sound reinforcement.
          + You could send the preamp out into a tape recorder and record
            it.
          + You could send the preamp out into a bunch of effects, and
            then connect the effects' output back into "power amp in,"
            thus putting the effects in between the preamp and the power
            amp stages.
       Some combination amps, though not all, also have a power amplifier
       in jack which allows you to send a signal from a separate preamp
       to the power amplifier directly. Most combination amps also have a
       power-amp out jack which allows you to send the power signal to an
       external speaker, either in tandem with the internal speaker or
       instead of it. Combination amps that have all three features are
       almost as flexible as separate stage rigs.
       
       
   15. What is biamping, and how is it done?
       Biamping refers to using separate power amplifiers to amplify
       different frequency ranges. (See question 10 for a discussion of
       power amplifiers.) In particular, it allows you to use one power
       amplifier to amplify your high freqencies and another to amplify
       your low frequencies. In most bass amplifier rigs, the preamp
       signal is sent to one power amp and the output from that amplifier
       is sent to the speaker cabinets, where it may be divided among the
       various speakers by a crossover in the cabinet; high signals to
       small speakers and horns, low signals to larger speakers. (A
       crossover is a filter which separates a signal into high-frequency
       and low-frequency components: it may have a knob which allows the
       bassist to control the dividing point.)
       
       With biamping, instead of splitting the power amplifier's signal,
       you split the preamplifier's signal and send each half to
       different power amplifiers. Then, each power amplifier drives its
       own speaker load; again, usually small speakers or horns for the
       high frequencies and large speakers for the lows. Also, the
       crossover used in biamping is usually active (ie it requires a
       power supply) whereas those found in speaker cabinets are usually
       passive.
       
       Biamping has several advantages:
          + active crossovers don't have inductors, so they exhibit less
            intermodulation distortion;
          + active crossovers don't drain the power of the signal to
            operate ;
          + the full power range of each amp is available regardless of
            the, power requirements of other ranges.
       For more information on the engineering side of biamping, an
       excellent book is Martin Colloms, "High Performance Loudspeakers",
       3rd. edition, pages 188-191 on biamping.
       
       The last item is important because it takes more power to
       reproduce low-frequency sounds than high ones. A typical biamp
       setup might be to send to highs to a 4x10 cabinet and the lows to
       a 1x15, 1x18, or other large subwoofer. If you send your high end
       through the subwoofer, your tone will probably suffer and become
       muddy, whereas if you send your lows through the 10s they will not
       provide as much thump as the subwoofer will. By biamping, you can
       send the lows through the subwoofer and still get clarity and tone
       from the 10s without forcing the 10s to spend most of their energy
       driving very low frequencies.
       
       To get a good sound from biamping requires some fairly close
       matching between the crossover, the amplifiers, and the cabinets
       used. Done poorly, biamping can sound worse than using a single
       amplifier and cabinet. If you biamp, it is better to get a system
       designed explicitly for biamping than to assemble components one
       by one.
       
       
   16. How do I adjust the setup on my bass (action, intonation, etc?)
       There is an excellent article in issue #153 of the Bottom Line. It
       is long but very good. It can be obtained from the Bottom Line
       archives by anonymous FTP; the address is ftp.uwp.edu and the back
       Bottom Line issues are in the /pub/bass directory.
       
       
   17. What is the difference between the various types of strings?
       There are basically three factors that affect string sound and
       playability. The first is whether the strings are flatwound or
       roundwound, the second is the gauge of the strings, and the third
       is the metal the strings are made from.
       
       Almost all bass strings are made of a central string which is
       wrapped in a second layer to make the string thicker. The central
       string is called the core of the string. These are usually round,
       although some hexagonal core strings exist. The wrapping comes in
       two kinds; some strings are wrapped with flat ribbon and some are
       wrapped with a round piece of wire. The first kind, called
       flatwounds, have a dark sound and are fairly smooth, which makes
       them easy on the fingers and the fretboard. The second kind,
       called roundwounds, have a much brighter sound, but tend to wear
       down your frets or fretboard and chew up your fingers.
       
       Most people prefer roundwound strings for their brighter sound.
       Flatwounds are mostly used for fretless basses, for which the
       damage caused by round- wounds is especially problematic. There
       are also two kinds of compromise strings, called groundrounds and
       half-flatwounds. Both of these kinds of strings are flat on one
       side and round on the other: this can be achieved by taking a
       roundwound string and grinding it flat, by applying pressure to
       the string to flatten it, or by wrapping with wire which is
       alternately round and flat, so that one side of the string is flat
       and the other is round. These types of strings are not easy to
       find but some players do use them.
       
       The second question is the gauge of the string. The gauge is
       measured by the thickness of the string in inches. A typical set
       of light gauge strings might have thicknesses of about 0.040,
       0.060, 0.075, 0.090 for the G, D, A, and E strings. A medium gauge
       might be about 0.050, 0.070, 0.085, 0.105. Heavy gauge strings are
       extremely difficult to find now, for some obscure reason. Most
       companies make three gauges of strings: light, medium-light, and
       medium. Some companies will sell you individual strings, which
       lets you mix and match your strings to get a unique combination of
       gauges, but not too many people do this.
       
       Lighter gauge strings tend to have a brighter but thinner sound.
       Heavier strings have a more solid sound to them. A major advantage
       to light gauge strings is that they require less tension to
       produce a given pitch, so that they require less force to fret,
       pluck, and bend, whereas heavier gauge strings call for a little
       more finger strength.
       
       The third factor is the metal used to make the strings. Almost all
       strings are made of either stainless steel or nickel. Stainless
       steel has a brighter sound at the expense of being a little harder
       on the fingers. The difference is not very great, however. You can
       also get strings which are plated with chrome or gold, or various
       black metals. These are more for effect than because the plating
       does anything to the tone.
       
       Acoustic strings can also be made of nylon or gut as well as
       metal. Gut strings are quite expensive but sound very nice. You
       can also get strings made of silicon and other exotic materials
       for unusual basses, but non-metal strings will not work with
       magentic pickups so most people don't use them.
       
       There are a few other factors to consider when buying strings.
       Many strings come with a silk wrap around the end of the string
       which helps to keep the wrapping on the string from coming
       unwound. Cheaper strings don't have this winding. However, if the
       string is made with a hex core (as opposed to a round core) then
       the wrapping is much less likely to come unwound (it grips a hex
       core better) and in that case, the silk wrapping is not as
       important. Another important thing to remember is that the strings
       have to go on your bass! Most basses require single-ball strings,
       with the ball end going at the bridge and the non-ball end being
       wrapped around the tuning peg. However, Steinburgers and most
       other headless basses require double-ball strings, one ball going
       behind the nut and the other behind the bridge. And, to keep
       things confusing, some headless basses, notably Kubickis, use
       single-ball strings by putting the ball end at the end of the next
       andtaking the non-ball end onto a post on the body of the bass.
       You cannot use single-ball strings on a double-ball bass and
       vice-versa, so make sure you know what you need before you buy.
       
       You also need to buy strings of the appropriate scale. The scale
       length of a bass is the distance from the bridge to the nut, ie
       the length over which the string vibrates. Most basses are "long
       scale" or 34-inch scale length. A few basses, notably old Gibsons,
       are "short-scale" or 30-inch scale length. Modulus Graphite basses
       are all built to a 35-inch scale length, as are a few other
       basses. There is also a "medium-scale" or 32-inch scale length,
       and some acoustic bass guitars are built to this scale. When you
       buy strings, they need to be the same length as the bass they're
       going on, so make sure you know the scale of your bass, and buy
       the appropriate strings for it.
       
       Also worth noting is the fact that there are only three major
       American manufacturers of strings, and a few more European ones.
       Although there are many brands of strings, a lot of those brands
       buy their strings from one of the main manufacturers and repackage
       them under their own name. Thus, there is less variety in strings
       than the number of brands available might suggest. Obviously the
       advertising does't affect the sound, so shop intelligently when
       you go looking for strings.
       
       
   18. How does a bass pickup work? What is the difference between the
       various kinds of pickups?
       A bass pickup works by detecting the changes made by the moving
       string in the magnetic field of the pickup. A normal bass pickup
       consists of one or more magnets wrapped in coils of thin wire. The
       vibration of the metal strings changes the magnetic field of the
       pickup, and the changing magnetic field produces a voltage across
       the two ends of the wire wrap. This voltage can be detected and
       amplified by a bass amp, and then converted back to sound by a
       speaker.
       
       This signal needs to be amplified in order to be audible. Passive
       pickups do not amplify the signal at all: they require the bass
       amp to do all of the amplification. Active pickups contain a small
       amplifier inside the pickup housing. This amp boosts the pickups
       signal to a higher level which is then sent down the instrument
       cable into the amplifier. (Good amplifiers have two input jacks,
       one for active basses and one for passive basses, to reflect this
       difference.) You can also get basses which have onboard preamps
       which take the pickup signal and pass into into an amplifier which
       is on the bass but not part of the pickup. These onboard preamps
       can also contain tone controls and other electronics; a few
       expensive active pickups also contain tone controls inside the
       pickup housing.
       
       You can make the pickup stronger or "hotter" by doing any of three
       things: using a stronger magnet, wrapping it in more windings of
       wire, or raising it closer to the strings. Using a stronger magnet
       causes the magnetic field to be stronger, raising the pickup puts
       it into a stronger area of the magnetic field, and using more
       wrappings of wire causes the moving string to induce a greater
       voltage difference within a given magnetic field. Any of these
       lets the string create a larger voltage differential across the
       pickup, resulting in a louder signal. However, they can also have
       an effect on the tone of the bass which you may or may not like.
       Also, if you set the pickup too high the string can actually hit
       the pickup casing when slapped or plucked hard, and this is
       usually not good. There is no optimal height for the pickups: you
       can put them anywhere you like as long as you are getting
       sufficient signal strength and you're happy with the tone of the
       bass. You can also balance your pickups by setting them at
       different distances from the different strings, which is useful if
       one string tends to be louder or quieter than the others. Most
       basses have bridges which let you adjust the string height, but
       this affects the action of the string as well as the distance from
       string to pickup. Some pickups allow you to adjust the height of
       the individual magnets so that you can set the strings at
       different distances from the magnets while keeping the action the
       same on all strings.
       
       Pickups come in two kinds: single-coil and double coil.
       Double-coil pickups pass the signal through two sets of magnets
       and wire coils (hence the name) whereas single-coil pickups use a
       single set of magnets. The advantage of most double-coil pickups
       is that the coils are wired backwards, and the magnets are out of
       phase with one another. Since the magnets are inverted in the two
       coils, they pick up the string signal out of phase, but they pick
       up any noise and hum in phase. Because the coils are wired
       backwards, the signal from one of the coils is effectively
       inverted before the two signals are added back together: this puts
       the string signals back into phase but effectively cancels out any
       noise that the pickup received. These pickups are sometimes known
       as "humbuckers" for this reason. Not all double-coil pickups are
       humbuckers, however: you only get the hum cancelling effect if the
       two coils are out of phase _and_ the magnets are out of phase. In
       some double-coil pickups the two coils are in phase, not out of
       phase, so these pickups do not cancel hum in the way that
       humbuckers do.
       
       Another side effect of having two coils in one pickup is that the
       two coils do not pick up exactly the same signal from the string,
       since they are not located in exactly the same place on the bass.
       As a result, when the signals are added back together, some of the
       high frequencies of the signal are cancelled out along with the
       noise and hum. This gives the pickup a particular sound associated
       with humbucking pickups that some people find unattractive, but
       others find desirable.
       
       Some double-coil pickups do not place each coil under all four of
       the strings. These pickups are sometimes called "split coil" and
       the most common configuration is to have one coil under the E and
       A strings and the other under the D and G strings. The pickup on a
       Precision bass is of this type. This pickup design doesn't cancel
       hum quite as effectively as a regular double-coil, since the coils
       are farther apart, but it also doesn't cause cancellation of the
       high frequncies of the string signal since the signal from each
       string is only picked up by one coil, not both.
       
       Single coil pickups, split coil pickups, and humbuckers all have
       somewhat different characteristic sounds, though, so all three
       kinds of pickups are fairly widely used regardless of their noise
       levels. A bass with two single coil pickups or in-phase
       double-coil pickups can also cancel hum if the if the two pickups
       are of opposite phase and are set at equal volume: in this case
       each single-coil pickup acts exactly like one coil of a double-
       coil pickup. Since the pickups are farther apart than the two
       coils of a single pickup would be, the high frequency cancellation
       is somewhat different, less pronounced but affected more
       frequencies.Most Fender Jazz basses are built with two single coil
       pickups that are out of phase and can therefore be used to cancel
       hum this way. Some basses have "phase switches" which let you
       change the phase of a pickup's wiring, so that you can get the
       "out of phase" sound with the hum cancellation, or you can get the
       in phase sound but also get some noise, as you choose.
       
       Some double-coil pickups also have a switch called a "pickup tap";
       this lets you pass the signal through only one of the two coils,
       thus converting a double-coil pickup to a single-coil. And some
       pickups, both single and double coil, have a switch called a "coil
       tap" which takes the signal out of the pickup after passing
       through only some (usually about half) of the wire wrap. Since the
       sound of the pickup is affected by the number of turns of wire in
       each coil, having a coil tap lets you get two different sounds
       from one pickup.
       
       Some expensive basses also have non-magnetic pickups call piezo
       pickups or piezoelectric pickups. These do not contain magnets:
       instead, they work by having a small crystal in the bridge of the
       bass. When the string vibrates against the crystal, this vibration
       produces an electric signal through the crystal, which is sent out
       to the amplifier. Basses that use non-metal strings are built with
       piezo pickups, and some basses use piezo pickups in addition to
       magnetic pickups in order to get more variation in tone. However,
       piezo pickups have a much much higher impedance than magnetic
       pickups do, and piezo pickups require special onboard preamps or
       other amplification tricks in order to sound good.
       
       
   19. How do I record my bass to tape?
       This is a fairly difficult thing to do because most recording
       equipment is designed to work best with frequencies higher than
       those delivered by bass. However, with the right equipment it is
       not hard to achieve a nearly professional quality recording of
       your playing.
       
       The simplest thing to do is to get a tape recorder with a
       microphone input and plug your bass into it directly, or send it
       your preamp signal. This will only allow you to record on one
       track, but it's very easy to do and most people have the necessary
       equipment at hand. You can also record using a microphone placed
       in front of your amplifier, but you will tend to introduce
       extraneous noise and unless you are in a recording studio you are
       better off using a direct input.
       
       If you want to record multiple instruments, or multiple tracks of
       a single instrument, you will need to obtain access to a
       multi-track recorder. You can buy four-track recorders at most
       large music stores, and professional studios have 16, 24, or 32
       track recorders.
       
       Once you have access to a recorder, the main decision you have to
       make is whether to send your bass signal to the recorder directly,
       to pass the signal through a preamp, or to send the signal to
       speakers and use a microphone to record the sounds from the
       speakers.
       
       If you go direct, you will need to convert your signal into a form
       that the recorder can take as an input. This can be done using a
       tool called a direct box, which most studios have, which will
       convert it to a balanced, low-impedance signal of the form that
       most recorders expect, but leave it otherwise unaffected. Or, you
       can use your own preamp to raise the signal to line level plus
       doing whatever effects processing you like. Your preamp may have a
       balanced output, or if not, you can run the line level signal into
       most direct boxes as well. However, if you are in a studio the
       engineer may have access to line-level effects like equalization
       and reverb which are better than those found in floor effects or
       preamps. If you can get the engineer's attention for 15 or 20
       minutes consider using the studio's quipment instead as you can
       get better performance from studio equipment in many cases. The
       drawback to so doing is that it takes time, plus you have to
       explain to the engineer how you want the sound to be whereas your
       preamp is under your own control.
       
       Another common problem is providing a constant signal from the
       bass. In particular, if you do a lot of slapping and popping, or
       you like to play chords on your bass, you might have a hard time
       recording a clean track without a compressor. A compressor will
       quiet down the louder notes you play and boost the quiet ones to
       produce a constant volume in the recording. If you don't have
       access to a compressor, you can try to simulate this by adjusting
       the recording volume as you play the track (or having a friend do
       it) You can also increase the volume of a bass solo the same way:
       turn the recording volume up for the solo, then turn it back down
       when the solo is over.
       
       You might also want to use noise reduction to eliminate signal
       noise, either from your bass and amplifier, or from a compressor
       if you use one. If your recorder has dbx then you don't have to be
       so critical of the signal level because dbx noise reduction gives
       you about 90db of dynamic headroom and almost no tape hiss.
       
       You will find that some of the notes you play on the instrument
       are louder than others. This is called the "sweet spot". Most
       instruments have them, though graphite necks can reduce or
       eliminate them. Your recorder should have a VU needle or other
       indicator that will tell you how much volume is being recorded.
       Adjust your level so that the VU needle does not spend too much
       time in the red zone of the indicator: this is an indication that
       you are playing loudly enough to damage the recorder.
       
       
   20. What are some popular effects for bass and what do they do? Is
       there a difference between guitar effects and bass effects? In
       what order should I plug them together?
       There are five main effects for bass, plus some others that aren't
       as widely used. They are: compression, distortion, delay, reverb,
       and chorus/flange. Most of these effects come in both analog
       versions and digital versions. Analog effects act upon the
       incoming signal directly, modifying it to produce the output.
       Digital effects convert the incoming signal to a pattern of zeroes
       and ones (hence the name digital). The resulting code is processed
       and the new code is converted back to a signal. Digital effects
       are typically cleaner and have fewer side effects than analog ones
       do. They are also considerably more flexible as patterns of
       numbers are easier to manipulate than electric signals are.
       However, analog effects are usually cheaper, and to exactly
       replicate the sound of players from the 70's and earlier who used
       analog electronics, you have to use analog effects yourself.
       (Digital effects weren't in common use until the late 70's, and
       weren't commercially available until the early 80's.) However,
       either one is fine for use with bass. They will sound a little
       different, so try both kinds and choose the one you prefer.
       
       Effects come in two kinds, those designed to work with instrument
       level signals and those designed to work with line level signals.
       Floor boxes are almost always designed for instrument level, and
       rackmount effects for line level. However, check and make sure you
       know which you have. It is possible to damage your effects,
       especially floor effects, by running the wrong level signal
       through them.
       
       There isn't all that much difference between guitar effects and
       bass effects and you won't damage anything by running a guitar
       through a bass effect or vice versa. However, bass effects are
       designed to work better on lower frequencies than guitar effects
       are, so you will usually get a better sound by using an effect
       designed specifically for bass.
       
       Most effects devices have several names. Where there aren't too
       many the following paragraphs try to give them all, along with the
       reasons for using one rather than another. However, if you are in
       doubt, ask the salesman what an effect does and you should usually
       be able to recognize it as one of those described below.
       
       Compression is an effect that keeps the signal strength of your
       instrument constant. It can work in one of two ways: it can reduce
       loud signals, or it can amplify quiet ones. Compressors usually
       have both functions; effects that only quiet loud signals are
       called limiters and effects that only amplify quiet ones are
       called sustainers. Compression has two purposes. First, it keeps
       your volume level constant. This is used in recordings where
       constant volume is desirable, and it protects amplifiers and
       speakers from having an excessively high signal sent to them that
       could burn them out. (Most amplifiers have limiters built in,
       which is why they don't get louder beyond a certain point when you
       increase the volume control.) Second, they increase the sustain of
       your instrument; as the string vibration begins to die down,
       making the signal quieter, the compressor raises the quiet signal,
       making it sound as it the string is continuing to vibrate. The
       drawback to compressors is that they eliminate sharp changes in
       the level of your sounds. This tends to destroy slapping, popping,
       and other percussive sounds, and it also alters the individuality
       of your sound by changing the attack and the muting of your
       fingers.
       
       Most compressors have three knobs: one which controls how quickly
       the compressor will react to changes in the incoming signal
       (usually labeled attack), one controlling how much the compressor
       will boost the signal (sustain or compression) and one controlling
       the level the compressor will try to attain (level). Manufacturers
       tend to adopt their own methods of labeling knobs on effects
       boxes; your mileage may vary.
       
       Distortion causes your sound to become more "crunchy" or "grungy".
       What it does is to clip the high peaks off your signal, which
       makes the wave more like a square wave (which has the
       characteristic buzzing sound of distortion) and emphasizes the
       higher frequency harmonics of the signal. In the old days,
       distortion came from driving an amplifier close to its limit, thus
       trimming off the high peaks naturally, and you can still obtain
       distortion this way. Tube amplifiers clip more gradually and more
       gently than transistor amps do: this causes the resultant
       distortion to sound different. Most people prefer tube distortion
       to transistor distortion, though not all do. You can drive either
       the pre-amp or the power-amp to its limit with most amps: you will
       usually get better distortion by overloading the power amplifier,
       but try it both ways and see what you get. Be careful not to blow
       out your amplifier this way, however; turn it up high enough to
       get distortion but no higher. If your amp has a limiter, you may
       not be able to do this at all. (Players also used to get
       distortion by playing with speakers which had rips in the cones.
       It is not recommended that you try this.)
       
       Distortion pedals clip your signal in a more artificial way but
       produce a similar tone. They usually have three knobs, one which
       controls the mix between noise and instrument signal, one which
       controls the tone of the distorted signal, and one which controls
       the output level. (Names of knobs varies too widely to permit
       suggestions.)
       
       Delay effects take the incoming signal and send it out repeatedly,
       with intervals ranging from microseconds to 30 seconds or more.
       They can be used to add fullness to your sound, to produce doubled
       parts without having to hit each note twice, or, with long delays,
       enable you to accompany yourself by playing a 30-second part
       through a 30-second delay and then playing a second part over it!
       Delay boxes usually have three knobs: one controls the time
       between repeats (delay), one controlling the falloff in volume
       between repeats (level), and one controlling the number of repeats
       given (repeats).
       
       Reverb effects are similar to delay effects, but mix in a very
       large number of very quick, quiet repeats. They simulate the
       effect of playing in a small room, where the sounds from the
       instrument reflects off the walls, creating a large number of
       rapid echoes. They usually have the same three controls as a delay
       box, which work about the same way in principle but will have
       quite different effects on the sounds.
       
       Chorus and flange effects both simulate the sound of having
       multiple instruments playing at once. Consider two basses playing
       the same part. They will not be perfectly together; they will be
       very slightly out of tune and the players will hit the notes at
       slightly different times. A chorus pedal simulates this effect by
       taking an input signal and duplicating it, with the duplicate
       signal slightly delayed and slightly out of phase with the
       original. In addition, the amount of delay and phase shift varies
       over time. This is designed to simulate the second player being
       slightly off from the first one.
       
       The difference betwwen chorus and flange is one of degree only;
       chorus pedals use small delays and phase shifts to produce a very
       subtle effect. Flangers use even smaller delays but vary the
       length of the delay and the phase changes to produce a more
       noticeable effect. If you turn on a flanger and don't play
       anything, you will hear a characteristic "whoosh" sound which is
       the result of certain frequencies being cancelled in the two
       signals before being sent to the amplifier.
       
       Choruses and flangers usually have three knobs; one to control the
       extent of shift produced by the effect (depth), one to control the
       rate at which the shift changes (speed) and one to control how
       much of the second signal is mixed together with the first (level
       or intensity). Cheap choruses will omit the latter knob. Some
       choruses will have a fourth knob which controls the overall signal
       from the effect as well.
       
       Many effects boxes, most commonly choruses and delays, contain a
       stero split which allows you to send the original or "dry" signal
       to one amplifier and the affected or "wet" signal to another. This
       is commonly used to send the dry signal to the PA and the wet
       signal to the stage amplifier, or vice-versa. Or it can be used to
       power two different stage amplifiers to get a stereo sound, though
       this involves lugging twice as much equipment around.
       
       Most players use the following sequence for their effects:
       compression first, then distortion, then chorus/flange, then
       delay, and last reverb. However, there is nothing magical about
       this ordering, and you should feel free to experiment with
       alternate orderings to get different sounds.
       
       For more information on effects, consult the excellent book
       "Getting Great Guitar Sounds" by Michael Ross, which discusses the
       acoustic properties of electric instruments and the workings of
       amplifiers as well as effects.
       
       
   21. What is the difference between digital and analog electronics?
       There are quite a number of differences between digital and analog
       electronics, which make analog better for some applications and
       digital better for others.
       
       First, a little information on bass signals. When you pluck the
       string on your bass, it vibrates back and forth. The vibration of
       the string causes sounds waves to be transmitted through the air
       at the same pitch as the string, and that's what your ears detect
       as sound. The idea of amplication is to get an electronic
       representation of the string's vibration, and then make the amp's
       speaker vibrate in exactly the same pattern, thus creating the
       same sound as the string (only much louder :)
       
       The job of the pickup is to "read" the position of the string at
       any moment in time, and translate that into a voltage. When the
       string is not moving, the voltage is zero and there's no sound.
       The faster the string is moving, the higher the voltage is, and
       moving in one direction induces a positive voltage and the other
       direction, negative. Thus, as the string goes back and forth and
       back and forth, the voltage in the pickup goes positive and
       negative and positive and negative. This voltage signal exactly
       replicates the movement of the string, so we now have an
       electronic "picture" of the string's movement which we can send on
       to the amplifier and speaker.
       
       En route, we are going to want to process this signal. At the very
       least we want to amplify it, ie, make it louder. We may also want
       to apply equalization or compression, or even a delay or chorus
       effect. There are two ways to do these sorts of things; analog,
       and digital. Analog techniques use physical electronic effects to
       convert the signal, using magentic fields, capacitors, and so
       forth. Digital effects use computer circuitry to create a
       mathematical representation of the signal, and then manipulate
       that signal mathematically. They then convert the processed signal
       back to a physical representation to send to the speaker.
       Converting the physical representation (ie, the pattern of the
       voltages from the bass) into a mathematical representation (a
       series of numbers stored in the computer circuit) is called
       digitization. Our earlier pattern of voltages going positive,
       negative, positive, negative gets translated into a series of
       numbers, something like 1, 0.6, 0, -0.6, -1, -0.6, 1, 0.6, 0,
       -0.6, -1, -0.6. Since those numbers are now stored inside the
       computer circuit, you can do anything you like with them before
       you send them over to the speaker to be converted back into sound.
       
       For an amplifier, the analog method of amplification involves
       either a vacuum tube or a transistor. Without going into the
       details of the physics, what happens is that the amplifier runs
       two signals through the vacuum tube/transistor. One is the
       incoming signal from the bass, and the other one is the outgoing
       signal to the speaker, which is much more powerful. The job of the
       tube or transistor is to exactly copy the voltage of the bass
       signal onto the speaker signal, which is then sent to the speaker
       where the physical signal is converted back to sound.
       
       In a digital amplifier, the electronic signal from the bass is
       digitized, but there isn't any manipulation of the digital signal.
       It's just sent over to the speaker circuit and sent out there
       unaltered, except with more power.
       
       The real power of digitization is that you can do anything you
       want with those numbers. Wanna send the signal out backwards? No
       problem, just reverse the sequence of the numbers. Effects like
       delay, reverb, chorus, and flange are very awkward to create using
       magnetic fields and circuits, but very easy to produce using a
       computer with a memory bank. That's why most of the uses of
       digital technology have been in effects boxes or processing
       equipment like MIDI, rather than amplifiers or basses. However, if
       you have a digital amplifier already, then it's real easy to build
       in a digital EQ or reverb while you're there. You've already
       digitized the signal, so you may as well play with it. There is
       even one company that makes a digital pickup now; it uses a laser
       to detect the position of the string and converts that directly to
       a digital signal onboard the bass.
       
       Why use digital electronics? Three main reasons. First, they're
       very powerful; numbers in a computer are a lot easier to
       manipulate than voltages in circuits. Second, they're much less
       subject to noise and interference than analog electronics, because
       they're not relying on magnetic fields and other physical effects
       that can be disturbed by grounding problems, radio interference,
       or other Bad Things in the area. They're also not subject to
       signal degradation inside the circuit, as analog electronics are.
       This is the same reason that CDs are so much better than analog
       cassetes. Third, they're much easier to miniaturize than analog
       electronics are. Analog reverbs are huge. Digital reverbs can be
       easily packed into a stomp box.
       
       What are the drawbacks of digital electronics? They're expensive.
       Essentially, any digital effect box or amplifier has a small
       computer built into it to do the mathematical processing. However,
       as the cost of computer technology continues to drop, so will the
       prices of digital effects, pickups, and amplifiers. So there will
       be a lot more digital equipment coming down the pipe in the next 5
       or 10 years. Probably not so much in pickups - it is likely that
       people are going to stick with analog pickups because the way they
       color the sound of the bass can't be easily digitized - but there
       will soon be all-digital preamps with digital effects built in,
       and that sort of things. And it will all work its way into the
       combo amps in time as well.
       
       
   22. What do the ratings of amplifiers and speakers mean? What is a
       watt, or an ohm? What factors must I consider in connecting
       amplifiers to speakers?
       Any electronic circuit has 3 properties of importance: voltage,
       current, and resistance. (Plus some more based on these three). As
       you may know, electric current consists of electrons moving along
       the wires. Voltage is the amount of energy carried by each
       electron. Current is the number moving passed in each second. The
       total power of the circuit is given by:
       
       Power = voltage * current
       
       thus, increasing either the voltage or the current will increase
       the power of your amplifier.
       
       Resistance is the tendency of a circuit to resist the flow of
       electrons (hence the name). The formula for resistance is:
       
       Resistance = voltage/current, or, current = voltage/resistance
       
       Thus, for a given voltage, a circuit of high resistance gives low
       current, and a circuit with low resistance gives high current.
       
       Voltage is measured in volts: you get 110 volts out of the wall
       (220 if you're in Europe). This is usually transformed by the
       amplifier to some other voltage, and there's not much you can do
       to change it. However, you can alter the resistance of the circuit
       by changing the resistance of the speakers. Changing the
       resistance will change the current flow, and therefore the power
       of the circuit. Resistance is measured in ohms: typical speakers
       and cabinets have 16, 8, or 4 ohms resistance. The current of a
       circuit can be deduced from these. Power is measured in watts:
       most amplifiers have the maximum amount of power they can deliver
       in the name somewhere (ie a Crate B-20 can deliver 20 watts of
       power). How loud you are depends on how many watts of power your
       are delivering.
       
       Substituting the second equation above into the first one yields:
       
       Power = (voltage^2) / resistance
       
       which gives the relationship between resistance and power
       delivered, assuming the amplifier's voltage is held constant. In
       fact, the delivered power of an amplifier may be less than this if
       the amplifier is not properly matched to the load it is driving.
       Most amplifiers are designed to drive a 4 ohm load of speakers. If
       you use speakers of more or less resistance than the designed
       load, you will not get as much power as you would get driving the
       designed load, and if you supply your amplifier with too little
       resistance, you may blow it up. It is always best to supply your
       amp with speakers of exactly the resistance it was designed to
       drive.
       
       Say you have a 55-watt amplifier driving a 4 ohm speaker (which
       might be typical). If you replaced the 4 ohm speaker with an 8 ohm
       speaker, you would double the resistance of the circuit, which
       would halve the current flow. Since power=voltage*current, this
       would cut the power in half; thus, your 55 watt amp would only be
       delivering 27.5 watts. This is not so efficient (nor so loud),
       which is why you would have the 4 ohm speaker in the first
       place... Conversely, if you put in a 2 ohm speaker you would
       double the current, and double the power to 110 watts, if the amp
       was designed to handle a 2 ohm load. Most amps aren't, meaning
       that in practice you would probably get much less that 110 watts.
       
       To make matters worse, the power ratings can be measured with
       different measurements. The two most typical are peak power and
       RMS power. The difference between these two is that RMS (root mean
       square) power is calculated by measuring the area under the
       alternating power graph (in effect converting it into DC power)
       whereas peak power is just that - the peak of the graph. You can
       convert figures by multiplying (RMS -> Peak) or dividing (Peak ->
       RMS) by 1.41 (square root of 2). Peak power figures sound more
       impressive (240VAC is really 340 volts peak) and some
       manufacturers use them, but RMS power is more "accurate".
       
       Why wouldn't you want to have as low a resistance as possible? The
       answer is that this would increase the power of the circuit (by
       increasing the current) and electric components can take only so
       much power before they blow up. Amplifiers and speakers are both
       rated by the maximum amount of power they can take without going
       crispy. Thus, if you have an amp which delivers 100 watts into 4
       ohms, and you attach a 2 ohm speaker to it which is rated for 120
       watts, you will now have a circuit carrying 200 watts of power
       whose components can only handle 100 (amp) and 120 (speaker).
       Something will fry in short order. Thus, you want to make sure the
       resistance of your speaker load is high enough that your amp can
       take the total power of the circuit, and each speaker can handle
       its share of the load.
       
       Another reason for not going as low as possible impedance-wise is
       that the actual formula for maximum power transfer is:
       
       TotalPower = (Voltage**2)/(SpeakRes+AmpRes)
       
       Solving for speaker power, we get
       
       SpekerPower = (Voltage**2)SpeakRes / (SpeakRes+AmpRes)**2
       
       Assuming that the AmpRes (amp output resistance) is constant and
       solving for maximum SpeakerPower results in SpekRes = AmpRes. With
       transistor amplifiers the amp output resistance is usually
       neglible (ie. << 1 ohm) but most tube amps have output resistances
       of 2 - 16 ohms. This means that you must match the impedance of
       the speaker with the output impedance of the amplifier.
       
       If you have only one speaker, that speaker is carrying the entire
       power of the circuit. However, if you have more than one speaker
       (and they are wired in parallel, which they should be) the load is
       divided between them. If both speakers have the same resistance
       (ie, it is equally hard to push power through them) then each will
       take half the power, and the total resistance will be half the
       resistance of either speaker. (If you have N identical speakers
       with R ohms, the total resistance is R/N.) So, if you have an
       amplifier which delivers 50 watts through 8 ohms (meaning that it
       delivers 100 watts through 4 ohms, or 25 through 16 ohms) and you
       hooked it up to two 8 ohm drivers, the total resistance would now
       be half of 8 ohms, or 4 ohms, and the amp would put out 100 watts,
       with 50 going to each speaker.
       
       If the speakers do not have the same resistance, then more of the
       power will be pushed through the low-resistance speaker. The
       formula for the total resistance of two speakers with resistance
       R1 and R2 (again, assuming they are wired in parallel) is:
       
       R = 1 / [ (1/R1) + (1/R2) ]
       
       So, if you are hooking a 4 ohm speaker and an 8 ohm speaker
       together in a cabinet, the total resistance will be 1 / [ 1/4 +
       1/8 ] = 1 / [3/8] = 8/3 ~= 2.67 ohms. Thus, an amp rated for 100
       watts through 4 ohms would put out 150 watts under this speaker
       load. The power is divided among the speakers in proportion to the
       resistance: in this circuit the 4 ohm speaker would get 100 watts
       and the 8 ohm speaker would get 50 watts. If you hook together two
       8 ohm speakers the resistance is 1 / (1/8+1/8) = 4, as said above.


-- 
* "Let's see if we can spot any colorful exotic natives in colorful       *
*  exotic costumes singing colorful exotic songs with their colorful      *
*  exotic hands out for bakshoesh." - Zebadiah Carter                     *
*  PGP public key available - try finger killer@niksula.cs.hut.fi         *

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