Buffering and Impedance
Understanding what a buffer does and how it affects your guitar signal is not as difficult or mystifying as it may seem to be. There are some pretty sketchy "explanations" of these topics, often loaded down with opinions, misinformation, and misleading experiences. Here we'll try to keep it simple and factual, without getting into any math at all. While it is nice to understand something, it's much nicer if you know how to apply that understanding to your situation. That's what we'll go for - a level of understanding that helps you in designing your signal chain, selecting modules, and even making some module configuration choices to help you get the tone you want, whether it is through GT modules or guitar pedals.
Wires and Cables
Everyone knows the basic function of a piece of wire or cable in a signal chain. They get your signal from Point A to Point B. What you might not know is that cables are silently doing something else at the same time. No piece of wire is a perfect conductor. All of them, no matter their length, diameter, purity, or manufacturing method, offer resistance to the signal passing through them. They all also have capacitance. It's not necessary to understand the details of resistance and capacitance. What is easy to understand is their effect and how to counter it.
The resistance and capacitance form a very simple electrical circuit called a low pass filter. A low pass filter has a cutoff frequency determined by the resistance and capacitance. Any signal that is below that cutoff frequency passes through the cable mostly unaffected and goes to Point B. Any signal that is above that frequency gets attenuated, or reduced. Those frequencies are not removed, just weakened. The result is that you lose some amount of your high frequency signal. Those frequencies also arrive at Point B, but are now weaker than they were at Point A. The proportion of high and low frequencies has been changed. How much do you lose? You might be able to calculate that if you analyzed your cable carefully, or perhaps had good technical specs about your cable. But we're keeping it simple here. Just use your ears and see if you can hear the difference between different cables of different lengths. In many cases the difference will be inaudible or so minor that it isn't worth worrying about, particularly if you use good cables and avoid long cable runs.
There are two things you can do to minimize that loss of highs, regardless of exactly what is lost. You can use shorter cables, and you can use cables of better quality that have lower resistance and capacitance. The length and quality of the cable are key factors in determining the resistance and capacitance of the cable. Most cable manufacturers don't supply much detailed info about their cables, so that may be difficult to find. If you do find that info, the specs will probably be "per foot" or "per meter" or similar. Which gets us back to length. Shorter cables cause less loss of highs by offering less resistance and capacitance than a longer cable made the same way. No matter which cable you use, not all of your signal will get from Point A to Point B.
A voltage divider is another very simple circuit found or purposely used throughout your signal chain and in your effects. Think of a voltage divider as a wire or cable with a resistor at the end connecting the cable and Point B (your signal destination) to ground. That resistor is like a fork in the road for your signal. Some of your signal will continue to Point B, and some will go to ground. The signal that goes to ground is lost and gone forever. There is a simple equation that allows you to calculate how much of your signal will go to Point B and how much will go through the resistor to ground. But you probably won't have the information to plug into the equation, so let's not worry about that. What you need to know is that if you lower the resistance of your cable (see above) or increase the size of the resistor to ground, more of your signal will get to Point B. What can you do about that? We'll get to that in moment, but first a little more info.
Pickups and Guitar Cable
We've been talking about "signal" in a very general way. What is it, really? You probably know that your pickups contain magnets and a bunch of wire called "windings", and your guitar strings are metal. Without diving into Physics 101 and getting all wrapped up in mathematics and details, we'll just summarize by saying that when you vibrate a metal string near a magnet, the magnet generates a very weak electrical signal in the windings of your pickup. That electrical signal magically captures how fast the string is vibrating and turns that into an electrical frequency, the frequency of the note you played. The details of the string, how you plucked it, the magnets, the windings, the distance between the strings and magnets, and a bunch of technical stuff also results in a strength for that signal. The strength is a voltage. So that plucked string results in a signal of some voltage and frequency, which are constantly changing as you play and the vibration of the string changes. That signal comes out of your pickup windings, wanders through your guitar circuitry to the output jack, and then goes to your guitar cable where you immediately start losing voltage above some frequency as we described above. What happens is that the voltage of the high frequency part of your signal is lowered more than the voltage of your low frequency content, resulting in a bigger loss of highs that you may or may not be able to hear.
So far we've been talking about Point A (your pickups) and what happens between Point A and Point B (lowered voltage of signal, with highs lowered more than lows). What is going on at Point B? For this discussion, Point B is the first effect in your chain, whatever your guitar cable is plugged into. Obviously, we aren't going to discuss what happens in every case of the 1,000,001 things you can plug your guitar into. We're going to generalize a bit - OK, a lot. Remember that voltage divider we were talking about above and kinda left hanging? Here's where it comes into play. Your effect is like that resistor to ground in a voltage divider. Yes the effect does lots of other stuff, but for this discussion the pertinent property is this resistance from your incoming signal to ground at the front of your effect circuit. The design of the effect determines the amount of that resistance. If the design results in a high resistance, then more of your signal voltage will go into the effect. If the design results in a low resistance, you will lose more of your signal voltage to ground. That is called "tone suck". Your effect is a voltage divider, which allows some of your signal to get sucked to ground and lost forever.
The loss of signal in the voltage divider is different from the loss of signal in the low pass filter. In the low pass filter, frequencies above the cutoff point where reduced disproportionately to the lower frequencies. In the voltage divider, they all get reduced about the same amount. However, we are humans and we perceive these changes in our signal through our ears. Human ears are not the best audio processing receivers. When you reduce a signal, our ears don't perceive an equal loss across all frequencies. In fact, we can't even hear all frequencies. Generally, humans will think that the highs have been cut more than the lows, so the sounds become more muffled as you reduce them.
Yikes - not good! Or is it...? And what can you do about it?
Tone Loss and Vintage Fuzz Effects
In the early days of effects, the circuits were simple and crude, as were some of the key components, such as the germanium transistors that were available at the time. The field of audio electronics was in its infancy and knowledge and experience were somewhat lacking. The effects built during those years often had designs that resulted in low resistance to ground, resulting in a lot of tone suck. And sort of by chance, some of those old tone-sucking effects happened to be fuzzes of different types, including the famous Fuzz Face. Players had an option of "no effects" or "tone sucking effects". Those that chose to use effects got what they got, and some of those poor design choices resulted in technically "sucky" tone that became the de facto standards and were worked into their signal chain in ways that resulted in "classic" tones that are still recognizable and greatly sought after even today. Some of that tone-sucking became a preferred tone choice. Seems a little odd, but the only real rule in tone is whether people like it, and there is no doubt that there are people that really like it in some forms.
Of course, this resistance to ground wasn't the only thing contributing to that tone. Sure, that Fuzz Face's low resistance might cause you to lose half your signal voltage or more, resulting in that distinct muffled sound many associate with not only Fuzz Faces, but fuzzes in general since many of the fuzzes were introduced in those early years of effects design. But low quality resistors, capacitors, transistors, diodes, or other components caused other problems that varied from one unit to another, or varied depending on the temperature of where you played, or varied depending on what other effects you used, or varied for other reasons. There was a lot of tone-sucking and variability that must have been frustrating. Actually, if you are using those vintage effects or modern copies of them, they can still be frustrating and unpredictable. Whether all this is good or bad depends on your ears and your opinion. If you like it, it is good. If you don't like it, it is bad. And don't let anyone bully you into believing your opinion is wrong and theirs is right. It doesn't really matter if you understand why any of this happens. If you like it, you like it - if you don't, you don't. That's what matters. You are the only legit judge of what you prefer.
Preventing Tone Loss with Buffers
Let's suppose that you fall into the camp that doesn't like this tone sucking. You want all your tone left intact so that you can decide what gets done to it, not some guy that designed a fuzz box back in the 1960's. What can be done to preserve your frequencies and your voltage?
It turns out you get a lot of help. It didn't take long for effects manufacturers to realize that it would be difficult to stand out from their competitors if they were all competing in a tone-sucking world. Effects builders began including higher resistance to ground in their designs. That helps a great deal in preventing the tone loss. Most effects don't have that problem, unless they happen to be copies of some of those old vintage effects with low resistance to ground. Even some of those vintage effect types are being updated to prevent tone loss. In addition to vintage fuzzes, many wah pedals have been notorious for tone-sucking. Some of the best new wahs don't do this, or you get a switch option to control it.
But what happens if you have a nice effect with the proper resistance and it comes after some other effect that still sucks tone? Or it is first in line, but after a long, low-quality cable? Well, garbage in, garbage out. Customers might think your nice effect sometimes sounds good and sometimes sucks tone. That's not good or fair. Or maybe you just don't like the tone-suck of those vintage effects. Or maybe you can't afford super-expensive cables. Or there is some other reason that just fixing this effect resistance problem isn't solving your overall tone sucking issue.
It turns out that you can build another small circuit, called a buffer, that will help solve the remaining problem. Again, we won't go into the details of how they work. We'll focus on what they do and how to use them. The essence of tone loss is a loss in voltage, perhaps a voltage loss that accentuates the loss of high frequencies as we've described above. So you can counter tone-sucking by fixing the voltage loss. That's what a buffer does. It "restores" your signal, by not losing it in the first place.
Many effects began incorporating buffers into their designs. In some cases they buffer the signal at the input to the circuit. In others, there may be a buffer at the output of the circuit. In a few, both the input and output are buffered. Obviously, buffering at the input is intended to correct incoming signal problems. Buffering at the output can ensure the effect sends out a good signal to whatever is next in the chain (and fix signal problems that the circuit itself may cause).
Some manufacturers even went so far as to send the incoming signal through a buffer even when the effect was off. Maybe they figured they were doing you a favor by making sure your signal was "good" all the time. Boss effects famously do that.
Sounds like the problem is solved, right? Not so fast...
Many "newer" effects were never available in a tone sucking form. People were used to how those effects sounded with a nicely buffered signal and a high resistance to ground. But those old classics, mostly fuzzes, had a large fan base of that "sucky" tone. It turns out if you feed those effects a nicely buffered sound, they don't sound the same. Better? Worse? Again, that's a matter of opinion. But "different", yes, to greater or lesser extent. And for many, that difference is "worse".
There's another type of difference that may also be experienced. When your pickups are connected directly via your cable to, say, a vintage fuzz circuit with that low resistance to ground, your pickups are sort of "strained" to provide enough signal to drive the effect. The effect is sort of "pulling" on your pickups. Depending on the pickups and the specific effect, your ears and the feeling in your fingers combine to play a wonderful trick on you. You "feel" the effect and it seems much more sensitive to your touch. It feels like your strings are touching you back. Your guitar feels "alive". It can be a *big* deal to the player and his playing experience - super cool. But can your audience hear that? It's a tricky question. Certainly they can hear any loss of highs, whether they know that is happening or not. But can they hear what the player is feeling? Technically, probably not. But what that player is feeling will 100% guaranteed have an impact on how he is playing. Those changes in playing could very well be both seen and heard and "sensed" by the audience.
But if you stick a buffer between those pickups and that effect, the "straining" and "pulling" stop. The buffer sends your restored signal through and breaks that direct connection. Two things happen. First, you lose that feel as a player. Second, your effect gets hit with a stronger signal and responds with a different sound. Again, "better" or "worse" is whatever you think it is. If you have ever experienced that feeling of the pickups fighting with your first effect, you may not want to give that up for the different sound produced by the effect. Or perhaps it becomes a "regrettable loss" because you like the less muffled sound better. It's your choice to make.
There is another possible side effect. Buffers are circuits, too. There's no magic in their componentry. While the intent is to take the input and "restore" it to it's pristine state, buffers may not actually do that. They may also color the tone a bit. Different buffer designs do that to some extent, in different ways. Some may be more transparent, others may, for instance, warm up the tone a little by accenting the mids. This may be intentional or not, but regardless of intent there may be audible differences in the results. You may be able to take advantage of those differences. Perhaps you don't want all that treble back. Or you may want that slight mids boost. Or you may want great transparency so that you can control your tone by other means.
When to Buffer
Probably by now you realize that you have to decide if you may benefit from buffering, whether you like the "benefit" of buffering, and where to put it in your chain to get the effect you want and avoid any side effects you don't want. There's no right answer to any of that, other than what your ears tell you. But there are a few principles you can start with in your experiments.
- You may want to consider a buffer at the beginning of your chain to make up for any guitar cable signal loss before your signal gets to your effects.
- If you want "that feeling" or "that tone" from a vintage fuzz, you may want to make sure there is no buffer between your pickups and that fuzz.
- You may want to consider a buffer at the end of your chain to make up for any signal loss in your amp cables.
- Maybe that buffered signal might sound pretty good pushing some of your effects, like perhaps an overdrive.
- If you have a lot of "true bypass" pedals, they effectively form a long cable when they are off. You might want a buffer to make up for signal lost across that cabling.
- Maybe you don't want the treble back. Jimi Hendrix used a long, curly guitar cable to reduce his treble and wouldn't likely have wanted a buffer to bring it back.
Selecting a Buffer
Selecting a buffer is a bit like selecting any other pedal. You need to try them in your signal chain and see how they sound. There's not much else you can do. You may lean toward a buffer with specific properties, perhaps the one with a mid boost, if you think that might specifically sound good in your chain. But you'll have to experiment and see what works best, or even if it helps in an audible way at all.
Keep in mind that you may have already selected a buffer and not realize it. A good number of effects, including all or almost all Boss effects, include buffers. You may already be buffering your signal. Sometimes those included buffers are only on when the effect is on. Sometimes those included buffers are on regardless of whether the effect is on or off. Sometimes you get to choose if they are on when the effect is off. If you have very many effects in your chain, chance are pretty good there is a buffer already in there somewhere. Of course not only buffers boost your signal. A variety of boost, overdrive, distortion, and other effects also boost your signal. Once your signal gets into those effects and/or buffers, you may not have to worry overmuch about tone loss. Or maybe you have enough effects buffering and boosting your signal that it gets harsh and you need to make some changes. You may also notice that if you move an effect in your chain, other effects may sound different - you may have changed the location of buffers in your chain.
Usually, barring problems with sending a buffered signal to a vintage circuit as described above, having an extra buffer here or there in your chain won't hurt anything. But all things in moderation. Too much buffering can start sounding harsh or can cause other effects to sound and behave differently enough that you can hear it.
Of course, at GT we like to provide options so you can get your effects the way you want them. Here are some things you can look for in some of our modules:
We offer several different types of buffers. They are all well-known designs, so you may already be familiar with them or maybe you can try one in a pedal somewhere to help decide if any color the buffer provides is desirable or not.
In some of our vintage fuzz circuits, we offer the option to have either the original low resistance to ground, or a higher resistance to ground that will prevent that classic, muffled, tone-sucking sound. You get to choose. Even if it isn't offered as an option on some module, we can probably still customize it if you inquire about it. We also offer an option to make that resistance value switchable on some circuits. We will probably add that to more circuits as we continue tweaking our designs. Choosing that lower resistance will definitely have the electronic effects on your voltage, but it doesn't necessarily mean you will get that feeling that your guitar is alive. That feeling depends on more than just the resistance to ground. But it may help.
Some of our modules have buffers in them by design. In some cases the buffers can be left off, made switchable, or otherwise customized to give you more options. You will also see that come modules come in multiple configurations, many of which may compare to effects you know. The difference between some of those configurations (and pedals) is simply the addition or removal of buffers from the design. Our Virago module compares to the Tube Screamer, in general. But there are many variations of the Tube Screamer circuit. The Tube Screamer has both input and output buffers. Some popular pedals are not much more than a Tube Screamer without one or both of those buffers. See the configuration descriptions for more information about the buffering.
That's a lot of words, but at least there's no math! Hopefully you can take some of this information and actually use it to design a signal chain you like, and understand some of the things that may be going on and causing wanted or unwanted tone changes. In the end, you really just have to give it a try and see how it sounds.
If you were really reading carefully, you'll notice that one of the words in the title of this article appears nowhere else in the article - impedance. We avoided it specifically because it is our experience that when that word appeared in a discussion about signal chains and buffering, it was a potential sign that the discussion was tending toward more technical detail than is necessary to figure this stuff out and manage it. That resistance to ground that the effect circuit offers helps determine the effect's impedance. Other components that we didn't discuss, a level of detail that quickly overwhelms the main point, also contribute to the impedance. So we just avoided it, admittedly being technically incomplete due to the omission, to keep it simple.
We also left out any discussion of output impedance, or the resistance between the output signal and ground. Players don't have much, if anything, they can do about output impedance. That is set in the effect itself. Had we included the equations and shown the math for those voltage dividers, you would see that having a low output impedance helps prevent signal loss to the next effect in your chain. Modern, well-design effects will have low output impedance so they "play nicely" with other effects. Buffers will have low output impedance, or risk causing the very problem they are meant to address.
Making sure the input impedance is high helps make up for something earlier in the chain that may be causing signal loss. Making sure the output impedance is low helps make sure that the next thing in the chain gets a good signal. Buffers help make up for problems when low input impedance or high output impedance cause signal loss, generally characterized by a loss of treble in your signal.