Why and When to Use a Guitar Buffer Pedal – Improve Your Tone
Guitar Buffer Pedal Overview:
Ever plug into a pedal or long cord and feel like your sound got more bassy or muffled, even with the pedal off? This article explains what a guitar buffer pedal does and why and when you would want to use one to improve your tone.
Simply put, a buffer is a circuit that will exactly replicate what is connected to the input to the output and more importantly, be able to apply that output with no changes (be transparent) to the next guitar pedal in the line.
When used correctly, a properly designed buffer pedal improves the high frequency response of your overall pedal chain. The main times you use one is if you have a long cable between anything, if you have a guitar pedal with a low input impedance (fuzz face) or non true bypass (many mass market pedals, wah wahs are known for “tone sucking”) and if you have a lot of pedals connected in series and are losing sound fidelity.
To explain this, first I give a method to test if you might want a buffer, then I give some examples where you would want a buffer and then I show the circuit explanation. If you want, skip down to the end and you can visually see the difference in frequency response with and without a buffer circuit. I’ll add some sound clips when I get a chance.
This video I made shows what a buffer will sound like compared to 40 feet of cable. Also, how to test your setup.
Notice in the video how the buffer makes the guitar sound have its treble back. Some people like this, others think its tinny. A guitar buffer will sound close to playing with a short, 1 foot guitar cord.
What does a Guitar Buffer Circuit do?
A guitar buffer circuit is very simply a circuit where the output is the same as the input. The better the buffer, the more similar the output is to the input. So why would you want that, sounds like it does nothing? The hidden beauty of the buffer circuit is that it has a very high input impedance and a low output impedance. This means it can reproduce a signal from a non-ideal source or send it through a non-ideal load. We will talk about this more later, but first here are a couple tests for you to try.
Simple ways to tell if you might want a buffer pedal:
These are some great tests for figuring out if you want a buffer pedal.
Test One: First, play your guitar through your amp with a very short cable, maybe one or two feet long. Then play through your pedal board with all pedals off. If it sounds different and you like the short cable sound, you might want a buffer.
Test Two: To test specific pedals, get two very short cables, as short as you can stand for this, maybe one foot long. Then, get a 1/4 to 1/4 adapter, guitar center and amazon sell Planet Waves Dual 1/4"" Jack Adapter which should work. Or, you could use a pedal that you are 100% sure is true bypass. Then, connect the cable to the adapter (bypass) to the cable and play a little bit. This will be tough because the line is short, but bear with me. The reason to use short cords is to rule out cable capacitance which has a big effect we will talk about later. Then, connect the pedal you are wondering about instead of the adapter. With the pedal off, if the sound is at all different, you might want a buffer. With the pedal on, its harder because then the effect is in place. But if you lose a lot of the crispness of the sound (sparkle, brightness etc. . .) then you also might want a buffer.
Test Three: To see how cable capacitance changes your sound, play the guitar into your amp with the 1 foot cord, then attach a long cord and listen to the difference. You should be able to hear less treble with the longer cord.
Of course, the other option is to just get a buffer and plug it in to see how it changes the sound.
Main Places to Use a Buffer Pedal
Before Really long cable:
You might want to use a buffer before a long cable. The cable will reduce your higher frequency tones because of capacitance. More about cable capacitance later.
Many Effects in a Row with True Bypass:
You might want a buffer before a lot of pedals with true bypass. The reason is that all the pedals are essentially similar to a long cable, with true bypass you are connected multiple cables in series which could have a high capacitance and effect your tone.
A pedal with low input impedance or one which exhibits tone sucking:
Some pedals have low input impedances such as fuzz faces. There is a debate about buffers and fuzz faces which we won’t go into, but you will be losing tone. Wah wahs are also known for tone sucking. If you try test 2, see if you can hear the difference with and without your wah.
Some places not to use a guitar buffer:
There is no use spending money on stuff you don’t need, and there are some places where using a buffer has no point. Here are a couple of them.
- Your guitar has a buffer built in. Some guitars already have a buffer and tone shaping built in. One way to tell is that you have to plug in a 9V battery to get it to work. My Ovation is an example of this but there are a lot more.
- Your pedal already has a buffer built in. Some pedals already have a buffer built in so there is no point adding another. For example, the famous tube screamer pedal already has a buffer that is on even when the guitar pedal is off. Other boss pedals have them as well. Some of these buffers aren’t the greatest, but they are already there.
Many buffers already in the pedal chain. The idea of a buffer is for it to always be on, so if you have a lot of them on, you are going to start adding more and more noise to your sound. This depends on the buffer design, but at some point, you will start hearing added noise. Don’t do
Why should a Buffer Circuit have high input impedance?
Figure 1. Resistor Divider Network. Rout is the guitar output impedance of your guitar and Rin is the pedal input impedance. The signal from the pickups is Vguitar. Ignore the cable for now and we’ll talk about that later.
Lets look at this in terms of circuits. A resistor divider is shown in Figure 1 where you have an output voltage source such as your guitar (Vguitar) with output resistance Rout and then an input resistance to a pedal called Rin. All pedals have an input resistance, the higher the better. The way the voltage appears to the pedal can be written as
Vpedal = Vguitar (Rin / (Rin + Rout))
What this means is that if Rout is large and Rin is small, then the voltage at the input of the pedal is small (which you don’t want). An example where this is a problem is a fuzz face pedal, where the input resistance may be 15kOhm or lower and is shown in Figure 2. Your guitar output voltage is about 100mV and the output impedance is about 15kOhm (It’s actually a little different because of frequency response but let’s save that for a different time). So, this means that:
Vpedal = Vguitar (Rin / (Rin + Rout) = 100mV * (15k / (15k + 15k)) = 100mV * (1/ 2) = 50mV
Only half the guitar voltage actually appears at the input of the fuzz face!
Figure 2. Resistor divider showing input of a pedal with low input impedance where you are losing your signal.
Figure 3. Resistor divider showing input of a pedal such as a buffer with high input impedance where your signal is reproduced fully.
Now, what if you have a high impedance guitar buffer, with an input resistance of 1M instead of 15k shown in Figure 3?
Vpedal = Vguitar (Rin / (Rin + Rout) = 100mV * (1M / (15k + 1M)) = 100mV * (0.99) = 99mV
Now, almost the entire guitar signal appears across the input because it has a high impedance. That’s quite an improvement, isn’t it? You will hear a difference in your tone.
Side note now, some of you fuzz face aficionados might pipe up about how the low input impedance of the fuzz face gives it some of it’s character. Completely true, but many other pedals have low or undesirable input impedance, especially those without true bypass. Also, did you ever notice you lose treble with your fuzz face. . . read on to find out why. Check out the end too, where I talk about the buffers and the fuzz.
Why should a Buffer Circuit have low output impedance and high input impedance:
Now that we did the hard work before, we can use our resistor divider to explain why a buffer circuit needs to have a low output impedance. Lets ask this hypothetical question: what if our guitar had a lower output impedance of 100Ohms instead of 15kOhm and we plugged it into that 15K fuzz face (sorry but because of the guitar pickup, that low of 100Ohms won’t happen in real life). Here’s the calculation:
Vpedal = Vguitar (Rin / (Rin + Rout)= 100mV * (15k / (15k + 100)) = 100mV * (0.99) = 99mV
So, if we have a low output impedance, than almost the entire signal will appear across the input impedance of the next pedal, even if its low. Much Better!
These two main points are the basics of any buffer circuit. A high input impedance makes sure that the full signal will appear across the input, no matter what the output impedance of the previous circuit is. A low output impedance helps drive the next circuit because it allows the signal to appear across the next input impedance. This circuit is often called a driver, because the low output impedance allows the buffer to drive the next stage.
Cable Capacitance, What Happens at Higher Frequencies?
Now, let’s add something else into the mix. What happens when you connect a big, long guitar cable to the output of your pedal? Guitar cables are basically long conductors, where a ground wire is wrapped around the signal but is separated by a non-conducting material called a dielectric. This forms a capacitance which is around 40pF per foot. So what happens if you have a 20ft cable; you have an 800pF capacitance to ground. You can see this in Figure 4.
Figure 4. Guitar connected to 20 foot cable into a pedal with low input impedance. The DC signal at the pedal would be 50mV and the signal at 10kHz would only be 36mV. As the frequency of your signal goes up, you lose more tone.
The problem is that this capacitor also adds an impedance; which depending on the frequency, can be very low. This is the problem that makes you lose higher frequency components of your sound. In fact, as frequency goes up, impedance goes down for a capacitor (guitar cable) and you lose more of your high frequency guitar signal. The impedance of a capacitor can be written as:
Zcap = 1/(2*pi*f*C) where f is the frequency.
Because frequency (f) is in the bottom, as it goes up the impedance Z goes down. You can hear up to about 20kHz, so lets run an example at half this. What if your guitar outputs a 10kHz signal into a 20 foot cable? The impedance is (use 10k for frequency and 800pF for Capacitance):
Zcap = 1/(2*pi*f*C) = 1/(2*3.14*10,000Hz*800pF) = 20kOhms
This is kind of low for an input impedance so lets look at what happens at 10KHz when we have this cable connected from the guitar to that low input impedance of 15k.Figure 4 shows the circuit, where we can analyze it for 10kHz.First, simplify the input impedance of the fuzz face and the cable impedance using a parallel network. The input 10k of the pedal is in parallel with the 800pF capacitance of the cable and two impedance in parallel have total impedance (Z1*Z2) / (Z1 + Z2) so:
Rcableandpedal = (Rin * Zcap) / (Rin + Zcap) = (15k * 20k) / (15k + 20k) = 8.57kOhm
This means that the guitar output sees an impedance of only 8.57kOhm at 10kHz when you connect the guitar to the pedal with a 20foot cable. We can find the signal at the pedal input by using our resistor divider network and guitar output impedance, we get:
Vpedal = Vguitar* (Rcableandpedal / (Rout +Rcableandpedal)= 100mV * (8.57k / (8.57k + 15k) = 0.36*100mV = 36mV
Because you connected the fairly long cable, you lose even more of the actual signal and it doesn’t appear across the input of the pedal. You are now losing a good amount of the signal from those expensive pickups you bought. . . The story gets better for low frequencies, but worse for higher frequencies. This configuration is called a low pass filter, because low frequency signals pass through but higher frequencies do not. You really don’t want this if you want to preserve the fidelity of your original guitar pickup signal.
Question time, where is it better to put a guitar buffer, before or after a long cable? The answer is before. The reason is that if you have a low impedance of the capacitance of the cable then it is in parallel with the input impedance of whatever is after it (remember from before). So, even if you have that high impedance guitar buffer, effectively the impedance is low and you will lose your signal. But, if you have the guitar buffer pedal before the cable, then the low output impedance of the buffer will be able to drive the cable and the input resistance of the next pedal or amp in the line.
Two main culprits of sound loss are the capacitance of your guitar cables and a low or non ideal input impedance of guitar pedals in your chain. If you add a guitar buffer in between, you can more easily drive these two situations and preserve your tone across all the frequency range your guitar produces. When you start using a buffer, you will immediately notice that you tone sounds a lot “brighter” or has more “sparkle”.
Some Notes on Buffers before Fuzz Pedals:
There is a long running debate on whether or not a guitar buffer should be used before a fuzz pedal. A portion of what makes a fuzz a fuzz is that the input impedance is low and will directly affect how the pedal works. If you were to buffer before this, you run into a couple of different scenarios. One is that you are now able to drive the input even though it is a low impedance. This give the fuzz a more gritty sound in my opinion. Another is that you can lose some of the interactiveness of the guitar with the fuzz. Things like how fuzz will change a lot with a little rolloff in your volume knob. However, you gain a couple of things as well. For one, you can keep all the bright tone of your guitar and the sound doesn’t sound as mushy. Another is that pedals like wah wahs before your fuzz don’t make such a drastic change in volume or tone when switched on and off. I find these two reasons to be worth it for me to buffer around the fuzz, especially because I don’t use my volume knob as a control for a lot of my playing. The fuzz pedals I put together have buffers at both the input and the output, but with a switch to turn them off if you want. What it all comes down to in the end though is what you prefer for your sound.