What's the purpose of a booster? And what's the proper way to use them?

[overdrive city]

Are they for overdriving an amp? Or just for making it louder? Or both? And how should you have your amp settings so that the effect doesn't muddy up the signal?

[CynicalMan]

A booster increases your guitar's signal's voltage. You can use it for overdriving an amp, or for just sounding louder. A good booster usually won't affect tone, but because of Fletcher-Munson effects (en.wikipedia.org/wiki/Equal-loudness_contour), you may have to tweak your settings. Usually, you won't notice, though.

[theundeadelvis]

Yes and yes! They can serve quite a few purposes, and there are a number of different boosters out there that are better at different things. Some just give you a boost of volume. Others will boost volume and affect your tone adding an emphasis of a certain frequency range. I prefer to use one to overdrive the preamp of a tube amp, and I also keep one on all the time just to add a little sparkle to my tone.

[theundeadelvis]

A good booster usually won't affect tone

I sort of disagree with this, but only based on my opinion of what "good" is. Technically speaking a good booster would be very transparent, but I prefer the slight change in tone I get with my boosters. Now if you want only a boost in volume, say for a solo, then yes you want a good transparent booster. 

[CynicalMan]

A good booster usually won't affect tone

I sort of disagree with this, but only based on my opinion of what "good" is. Technically speaking a good booster would be very transparent, but I prefer the slight change in tone I get with my boosters. Now if you want only a boost in volume, say for a solo, then yes you want a good transparent booster. 

I meant good in the sense of close to electronically ideal. I agree that tone changing in a booster can be useful, but, if a circuit was designed only as a booster, that would be a design fault.

[theundeadelvis]

@CynicalMan - I understand that. I probably shouldn't have said "disagree", because I was really only adding my opinion. You are completely correct in that a pure boost (in the technical sense) should only raise the signal level and not change the qualities of it.

I should also add my favorite boost of all is Mark Hammer's Crank. Definitely not a pure boost in the sense mentioned above, but man it sounds good, and it's pretty versatile for a boost.

[FlyingZ]

Are they for overdriving an amp? Or just for making it louder? Or both? And how should you have your amp settings so that the effect doesn't muddy up the signal?

A straight clean boost in an effects loop for leads or before the amp for overdrive is tricky. You will find typical boosters don't amplify every frequency the same and with a sensitive overdrive you will notice problems.

Keeping the lows clear without making the highs thin is by far the greatest challenge. Several people (and me) swear by a flat Boss EQ with a slight volume bump in the effects loop for a clean lead boost. Other then that an overdrive like TS9 is great for driving tubes and adding gain while cutting bass for clarity.

[Bullet79]

Booster 101
-boost before OD/Distortion pedal give you more gain/saturation... (and noise too..)
-boost after OD/Distortion for volume increase.. good for solo

[Mark Hammer]

All amplifying devices have a certain margin of error built in with respect to signal handling.  We refer to that as headroom, in the sense that rooms in any building are designed in anticipation of humans of some unknown (but roughly predictable...in ballpark figures) height can jump up and down, and not give themselves a concussion.  So the ceiling needs to be at least a certain height, but generally not more than some other height.  Same thing with amplifying devices.  They need to be able to handle at least THIS much signal cleanly, but probably not more than THAT amount.

Within that range, the user can enjoy benefits with respect to the S/N ratio by increasing the input signal level so that it is above what it used to be, but below what the maximum allowable is.  In that respect, applying some clean boost - provided the circuit doing it is quiet itself - can improve the overall S/N ratio of the system.  Any sound reinforcement pro will tell you that you always try to feed each stage with the hottest possible signal, within headroom limitations.

Of course, eventually you run out of headroom in one or more stages of processing.  It's generally a little easier to run out of headroom in your pedal chain, than in your amp or rackmount devices, because you don't have a lot of headroom to spare when using a 9v supply.  More about that later.

A great many clean boosters also act as buffers, in that they provide the sort of ultra-high input impedance that preserves the full bandwidth of your pickups.  Of course, if the booster is placed later on in the chain, as opposed to immediately after the guitar, that particular benefit is lost.  But still, you asked about how they're used, and that's one of the uses: keeping it crisp.

Boosters can be used ahead of everything else or after other things.  When used after, it simply makes them louder.  It does that too when used before, but then you have that headroom-with-9v thing.

Boosters used ahead of pedals have other consequences too.  All distortions anticipate a certain input signal level, and have enough gain designed into them to get a characteristic quality of clipping.  If you provide a hotter signal than anticipated (by boosting), you can get more clipping.  When booster pedals are fed to other devices that use a sidechain (compressor, noise-gate, limiter, envelope-controlled anything), it increases the apparent sensitivity of that pedal, so that compressors squish more severely and autowahs sweep more easily.

Of course, a too-hot signal can have undesirable consequences.  FET-based phasers, and BBD-based pedals that do not employ any companding, are quite susceptible to unpleasant distortion if fed too high an input signal.

Certainly one of the favourite uses for a clean booster, though, is to push a tube amp from clean into overdrive, whether merely for tone, or for a solo.  Remember, even though they generally have more headroom, amps have clean headroom limitations too.

What sort of boosted signal is "best" to push an amp?  Good question.  Some boosters employ higher than normal supply voltages.  The Visual Sound True Tone uses a voltage tripler to provide wads of clean headroom so that all the guitar's dynamics can be preserved.  RG - its designer - once described it to me as making amps quiver in fear.  The Klon Centaur (which can be dirty, but can also be clean) uses a voltage multiplier too, to help provide more headroom for those who want it.  Is this good or bad?  Neither, just a parameter, that's all.  If you have an amp that is very touch sensitive, then the extra headroom in the booster allows you to "play" the headroom of the amp and get different tones by digging in.  Of course, you may wish to have your amp maintain a consistent tone in spite of your picking dynamics, in which case more headroom in the booster offers no great added value, although more headroom generally means greater maximum output which MAY be of use/interest.

What about the tone of a clean booster?  Normally, and as was mentioned earlier, we like clean boosters because they preserve those crystalline highs.  But does an overdriven amp want those highs?  Generally, no.  That's why the Klon and Truetone, and 9v-based boosters from other manufacturers like DOD and Modtone come with treble/tone controls, to tame the highs so that the amp doesn't start generating those fizzy harmonics of harmonics.

There.  I'm tapped out.

[overdrive city]

Thank you for the information! 

[Renegadrian]

Boosters are made to have fun with them! There's no limit to their use...And as they always are low parts count projects, build more than one! Sometimes you can build one on a boring rainy evening (as I did). You'll end up knowing each feature of every booster you build...And appreciate every one of them...and know when to use one instead of another...

[amptramp]

One other feature of some boosters is to provide a low output impedance so you can drive long cables without losing the high-pitch signal components.  This also gives some immunity to ambient noise by making it harder for an interfering signal to change the voltage of the desired signal.  Boosters can also provide amplification with low noise so that inherently noisy items like a BBD delay do not overpower the signal.

[Mark Hammer]

One other feature of some boosters is to provide a low output impedance so you can drive long cables without losing the high-pitch signal components.  This also gives some immunity to ambient noise by making it harder for an interfering signal to change the voltage of the desired signal.  Boosters can also provide amplification with low noise so that inherently noisy items like a BBD delay do not overpower the signal.

Some caveats there.

1) Very few contemporary pedals do NOT provide a low-impedance output, so the impedance thing will only matter if a) the booster is the only thing between your guitar and amp, or b) the input impedance of the first "effect" you wish to use is not particularly high and the booster has a much higher input impedance with proportionately better conservation of highs.

2) Running long cables is partly a function of current drive, as well as low output impedance.  Jack Orman's "Super Buffer" provides an example of what I'm talking about, but note that it is not intended to be a "booster".

3) Final S/N ratio is really all that matters.  If a booster can take advantage of any remaining clean headroom in a BBD-based device, so as to improve the S/N ratio, great.  But be aware that the real goal is to balance off S/N with signal quality.  You CAN goose the signal level of what you feed a delay or chorus pedal, and turn down the amp, but if the result is an undesirably clipped chorus output, then you have simply switched one battle for another, and not really won the war.

As with a lot things when it comes to pedals, it's rare that you get something for nothing, your cake and eating privileges, or whatever other maxim you wish to offer.  Just be prudent and thoughtful in how you use them, because sometimes they don't matter or help a bit, and other times the way in which they "help" can create other issues that now have to be addressed.

[Mich P]

Bullet79 wrote :
"-boost before OD/Distortion pedal give you more gain/saturation... (and noise too..)
-boost after OD/Distortion for volume increase.. good for solo "

Both in the same time would be heaven !
Mich P.

[Mark Hammer]

Well, "heaven" is achievable, but it would depend on the nature of the distortion "engine".

If I stick a booster in front of my Shin-Ei FY-2, it gets MUCH sicker-sounding, but not that much louder.  If I stick a boost ahead of anythng that uses germanium diodes to ground, it will also get more intense, but not that much louder.  If I feed a boost to something that has more headroom, such as something that uses a 2+2 diode silicon configuration, or an all FET distortion of soem kind, then there is a very good chance that the output will be both gnarlier and louder.