TheGigRig What is a Buffer

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GBTECH TALK BUFFER OR BYPASS?

ECHTLK

Buffer or bypass?TRUE-BYPASS OR NOT TRUE-BYPASS? THAT IS THE QUESWE UNRAVEL THE MYSTERIES OF BUFFERED EFFECTS P



beginning and look at the signalfrom your guitar.The pickups on your guitar will

have an impedance rating measuredas DC resistance in ohms. For example,the output of the neck pickup in myTelecaster is 6.2kohm (or 6,200 ohms).The bridge pickup is slightly ‘hotter’ at6.7k. I’m sure a lot of you will haveseen these gures on your pickups and

wondered what they mean. In generalterms, a higher impedance will meanmore output, but let’s look at therelationship that this gure has withthe guitar cable.

CABLE CAPACITANCEThe cable that you use to plug yourguitar into your amp or effects willhave a certain amount of capacitance,

so what does this do? In the simplestof terms, the capacitance in a signalcable will affect the top end of yourtone in the same way that thecapacitor linked to the tone controlinside your guitar lets you roll off highfrequencies (although it actually doesa whole lot more, including tuning thefrequency hump of the pickups, butmore on that later).

Your cable acts just like a capacitor

cable, then through the pedal/buffer

and even though the sound is the

part of designing a pickup is about

balancing the output against this


“YOU WANT TO MAKE SURE THAT ANY BUFFERIN YOUR SIGNAL PATH IS TRANSPARENT”

■ Let’s have a look at simple‘true-bypass’ and ‘buffered’switches in an effect pedal.

In the true-bypass diagram,following the signal path you cansee the guitar signal is connectedto the centre pole of the switch. Inthis case it’s a double pole, doublethrow switch (or DPDT). Thismeans that there are basically twoindependent switches that areoperated by the same footswitch.In one direction the two centrepoles are connected to the two toppoles enaging the effects circuit.Stepping on the footswitchdisconnects the top poles andconnects the centre poles to thebottom, which is a simple piece ofwire connecting the guitar signaldirectly to the output of the pedal.

Now to the ‘buffered’ circuit.

There are several ways to do this,but the basic principle is the same,which is to use only one switchand put it on the output side. Theguitar’s input is connected to theswitch (in this case an SPDT, orsingle pole, double throw) and tothe input of the effects circuit theentire time. The switch simplychooses between the output of theeffect or the output from thebuffer. As the switching duty caneasily be performed by a transistor,which is a much cheaper optionthan using a standard footswitch,most companies designing on abudget opt for this method, butthat’s not to say that top pedalsdon’t use a buffered circuit. Manydo and many sound fantasticbecause of the high quality of thebuffers they use.

BUFFERED AND TRUE-BYPASS SWITCHING IN DETAIL

SWITCHING STYLES

■ A ‘TRUE-BYPASS’ SWITCH

■ A ‘BUFFERED’ SWITCH



105GUITARBUYERSEPTEMBER 2009

BUFFERED BOARDIn my personal experience I get the best results going through no more than threebuffers on one pedalboard. In the buffered board example below we have six, solet’s cut that down to three.

The rst thing that we’re going to do is remove the buffer in the tuner witha simple AB switching box. Next, we’re going to put a couple of the effects intrue-bypass loops. I only know of a handful of overdrive pedals designed to takea buffered, low-impedance input. This isn’t to say that they don’t work with

a buffered input, but generally when a designer sits down to make an OD pedal,he plugs the guitar straight into it, so we want our ODs to see the signal directfrom our guitar. Getting the tuner out of the signal path with an AB box is a greatstart, but we also want to put the ODs in true-bypass loops so that when we bringthem in they see the pickup impedance directly.

So, with an AB box and a simple true-bypass double looper, we have cut ourbuffers from six down to three. Our overdrive pedals are working the way they

were designed to and our signal path is still buffered after the ODs, so we’re getting the correct lowimpedance to drive the long cable from our pedalboard back to our amp, all without experiencing thenegative effects of too many buffers. Here’s the buffered board before (top) and after (bottom):

TRUE-BYPASS BOARDThis ‘true-bypass’ pedalboard is an example of someonewho really has put a lot of thought and money intogetting some great boutique effects, but unfortunatelyas all the effects are true-bypass the impedance fromthe guitar has to drive not only the cable to thepedalboard, but all the patch leads between theeffects and the long cable back to the amp.

Thankfully xing this one is simple. All we need todo is place a really good buffer after the OD pedals. Thebuffer will drive all the capacitance so we get our topend back and the ODs still see the impedance straightfrom the guitar. So we have chosen an ‘always on’dedicated buffer unit designed specically for the job.

Remember that in true-bypass boards you should always use the best quality cable you can afford.It makes a big difference, especially up to the point of the buffer. There are loads of really good cablemanufacturers out there, such as Horizon, Klotz, Evidence Audio and, of course, George L’s. Don’tskimp here and your tone will thank you. Here’s the true-bypass board before (top) and after (bottom):


Many players love the tone ofguitarists with simple boards onlyrunning a few effects and I haveabsolutely no doubt that it’s thestacking of these buffers (or lack of)that adds to or detracts from theclarity and effectiveness of some ofthese great guitar sounds.

In response to this, manypedal builders started employinga ‘true-bypass’ design, somethingwhich has become very popularin modern boutique guitar effects.

This means that when the effectis bypassed the signal does not gothrough a buffer, but effectivelydisconnects the effect circuitcompletely from the signal path.Problem solved? Not quite…

You see, even though you’regetting rid of any adverse effectsthe buffers might have on the tone,by removing them completely youare now relying on the outputimpedance from your guitar todrive the capacitance from notonly your cables, but also thefootswitches and the patch leadsof all your effects.

WHAT’S THE ANSWER?The solution is a carefullythought-out combination of the

two: both true-bypass and bufferedpedals. Let’s have a look at twotypical pedalboards – onefeaturing buffered effects, theother true-bypass – and solvethe problems on each.

Both of these setups have someissues. On the buffered board, theguitar signal is going througha whole heap of buffers, eachadding its own thing to the sound,changing the dynamics andaltering the transient response ofthe note. The true-bypass board hasno buffers but has so much extracable, including the patch leads,

104 GUITARBUYERSEPTEMBER 2009

that the elusive‘plugged straight in’sound is nowhere insight. Because thetone is dull, the ampis set to be bright, butthe problem will nowcome when one of thepedals is engaged. Theimpedance of that

pedal changes whenit’s turned on and actslike a buffer (becauseit is), so because theamp is set up witha lot more treble the

sound immediately becomes tinny andharsh. My solutions to each of theseproblems are outlined here.

EXCEPTIONS TO THERULEBefore you race out and buymega-expensive short guitar cables,it is important to note thatultra-low-capacitance cables do notalways sound better. A certain amountof capacitance in your cable can bea good thing as it does more than justaffect the top end. It also reacts with

the frequency hump of the pickup.The more capacitance in the cable,the more it loads the pickup andmoves that frequency hump downtowards the lower frequencies. Lowerthe level of capacitance and the humpmoves towards the upper frequencies,accentuating the top end. What manyperceive as simply the ‘sound’ of thecable is in fact the effect of the cablecapacitance on the pickups.

There are examples of players likeBrian May who famously used hiscurly cable for most of his career. Thatcurly cable has loads of capacitancebut, used in his setup, actually workedreally well. Albert Collins useda 120-foot guitar cable because heliked the way it sounded.

There’s no doubt that these guys

are the exception to the rule andmost players prefer the sound ofgood-quality low-capacitance cables,but as you all know by now, when itcomes to great tone the rule book getsthrown out the window.

If you’re in any way serious aboutyour guitar sound, then I urge you toexperiment with this. Go into a guitarshop that has a few examples fromcheap to very expensive cables and useyour ears to nd which you like best.Once you’ve found the cable thatworks for you, employ the abovetechniques on your pedalboard tokeep your tone consistent. GB

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TheGigRig What is a Buffer