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VOLUME 7

Buffer the signal loss slayer

 

Should I use a buffer on my board? Does true bypass sound better than buffered? Are we alone in the universe? Where do you wanna eat? For years I've seen all kinds of questions asked about buffers on guitar effect forums and they usually get some of the wackiest answers so here's what a buffer is.

As mentioned in a previous article, every single piece of conducting material has dc resistance and ac impedance, measured in ohms. Resistances (or impedances) in series will divide a voltage proportional to their value over the sum of their values, such as Vrx = Vin x (Rx / R1+Rn).

Keeping those two statements in mind, picture the last component at the output of a guitar. That component has resistance. This is your guitar’s output impedance (remember, we call it impedance as it's relative to an ac signal). Now, let's connect it to another pedal which has a first component that has its own impedance. That's your pedal's input impedance. As you've probably guessed, that voltage division rule applies. Here's an example with numbers:

 

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Imagine a typical single coil pickups outputting a simple signal of about 100mV peak-to-peak. Those pickups are connected to a 250kohms volume potentiometer (disregard the tone knob for now) so you can say your output impedance is 250kohms. Now imagine a guitar pedal built on purpose with low input impedance (Fuzz Face-type circuits rely on this), let’s say 10kohms. Disregarding the cable’s negligible impedance and stray capacitance (creating its own high-pass filter, by the way) and applying our formula: Vout = 100mV x (10000 / 10000 + 250000) = 3.85mV.

See what happened? Because the input impedance is much smaller than our output impedance, we suffer a heavy signal loss.

 

In the vast majority of cases, this is bad!

 

Buffers are super simple circuits that will have very high input impedance and very low output impedance so that regardless of what comes before and after it, signal loss is kept to a minimum.

Remember when we talked about capacitors? Capacitors exhibit an attribute called capacitive reactance which is a fancy name for frequency-variable resistance - or impedance. In other words, any amount of capacitance will create an impedance for a given frequency signal. What sucks about capacitance is that it's literally everywhere and when it's someplace you didn't ask for, it's called parasitic.

 

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You might've heard long cables are bad for "tone suck" and is one of the reasons you should buffer your signal. Well, that's right! The longer the cable, the bigger its stray capacitance and impedance to your signal and worse ratio with the following input impedance. A buffer with very high input impedance will make up for the long cable's impedance and prevent signal loss at different levels of different frequencies.

Contrary to somewhat popular belief, buffered bypass is not a bad thing unless you use it right before pedals with purposefully low input impedance, which are almost exclusively Fuzz Face-family circuits. These behave in an occult way I'm not going to get into, but if you don't use one of those, buffers are your bros.

That's all there is to buffers. They won't "color your tone" or "add warmth". There are a few different cases in which the use of a buffer is warranted, but in all of them they accomplish one thing: they make sure you don't lose signal. Period.

 

So there you go - now go get some Internet points with that new knowledge!