Signal buffers – what they do, and some food for thought on true bypass.
by Dan Albrecht, owner/founder of Area 51, area51tone.com
Of all the questions that I get, the subject with the most confusion around it seems to be buffers. There has been a big debate for a number of years now about which is better; buffers or true bypass. I’m going to address that in this article too, but first let me explain briefly what a buffer actually does.
A buffer (as it relates to audio) is simply a circuit that couples one device (or circuit) to another, allowing signal to pass freely, while preventing one device from loading the other. What is this “loading” that I speak of? For our purposes, it’s a resistance or capacitance to ground that causes the signal to be attenuated or dulled down. Use a cheap 20 foot guitar cable, and chances are you can hear this for yourself. The example that I deal with the most are the old Vox and Thomas Organ wah wah pedals. They bypassed the signal in such a way that the actual wah circuit input was never out of the circuit – so it created a load on the bypassed signal. That’s commonly referred to nowadays as “tone suck”. Most wahs now are true bypass – the signal is routed completely around the circuitry – from input jack to output jack. So which is better? Well, it depends. I’d say that if you like your straight into the amp tone as it is, go with true bypass. But let’s say you have an overly bright sounding amp – the treble is a bit harsh. Then in that case, you could probably stand a little tone sucking. Jimi and Stevie Ray didn’t have true bypass wahs, and nobody is gonna accuse them of having bad tone. I know that in Stevie’s case, he was a fan of the cheap Radio Shack guitar cables. He used to send his friend and tour manager, Cutter, out looking for them on occasion. Stevie used blackface Fenders on stage. Those amps tend to be a little bright and harsh on the top end. I’ve modded a TON of them with shielded grid wires on the first gain stage and sometimes on the tone recovery stage too. That actually adds a little capacitance to ground, and bleeds off a wee bit of treble. It also prevents grid leak voltage from showing up on the input – which can cause noise problems. Marshall amps, like Jimi played, have a similar thing going on, but those amps started as tweed Twin/Bassman copies and evolved into what we know and love – which included mods for….more treble! So Hendrix not only had a tone sucking Vox wah in his signal path, but he also had a coily cord (another tone sucker). *I’m talking about the ones made in the 60s here, and I have no idea how the modern ones are capacitance wise. So there you have it – a case for the old tone-sucking bypass.
At some point in the early 80s, Dunlop (who had become the new steward of the Crybaby wah) decided to rid the wah wah of it’s tone robbing tendency. I’m only guessing here, but I suspect that they had tons of switches already on hand that needed to be used, so changing to a true bypass (which uses a 6 lug DPDT switch) was not an option that made as much sense. What they did was to add a buffer with a high impedance input – so as to prevent any signal loading, and thus still be able to use the many SPDT switches they had. That circuit is known as an Input Buffer. A source of great confusion in the world today is the use of the word “buffer” here. I get questions quite often about the buffer circuit that I sell. Does it degrade the signal? (no) Is it off when the pedal is bypassed? (yes) Much of that confusion comes from the use of the word buffer, without the context of where and how it’s being used.
Let’s face it, some so-called buffered pedals DO affect the tone in bypass mode. The tubescreamer is a classic example. Don’t take my word for it – hook up a true bypass loop box to it and listen for yourself. So I will say that a PROPERLY designed buffer will not degrade the signal at all. But although the buffer won’t degrade the signal, it MAY have an apparent effect on your tone! Confused yet? Here’s how that happens: Let’s say you have a few 20 foot cables in your rig, and another 15 feet or so of patch cables between pedals. If those cables are not top quality, low capacitance – you are losing some high end and signal level too. I’m not saying you have to spend insane amounts of money on cables – you don’t. But cable capacitance is something you need to pay attention to if your tone matters. My personal favorite for a long time now has been Klotz La Grange (now called Klotz AC110 or GY110) Going price is about $4 a foot for raw cable at the time of this article. Anyway, if you are losing signal in your cables, you will hear a difference with the buffer. The signal will be louder, and brighter. It’s actually NOT the buffer changing your tone, it’s the buffer PREVENTING the losses. The buffer is doing it’s job, in other words. So that is the answer to the question “will the buffer change my tone?”
So that brings up another buffer question I get often: “Where should I put the buffer in my rig?” The buffer kit that I sell was originally intended to be installed in a wah pedal so that the wah could be placed in front of a fuzz face. Fuzzes of that type are low impedance input, and load the holy hell out of anything connected to them (it’s a big part of the sound actually, and cool in it’s own way). But it will render a wah almost useless. So placing a buffer between the wah and fuzz cures that issue. But that’s not the only way the buffer kit can be used. I think one of the best places to use a buffer is at the end of the effects chain – right before the long cable going back to your amp(s). The Kendrick ABC Box amp-splitter has a buffer on each output. Definitely a good idea!
A buffer can also be used between each pedal. I don’t feel that is necessary in most cases. I think it’s important to add that each buffer will contribute a tiny bit of noise. You won’t hear it with just a few. But if you have 15 of them, you are going to hear noise – no doubts.
Another statement I hear a lot is “I’m going to put a buffer at the front of my signal chain to prevent loading all the way through the pedal board”. I’m gonna take the opportunity to do a little myth-busting.. A buffer is not a magical rainbow unicorn that your signal rides on, thus saving it from the trolls of signal loading. It needs to be in the right place. Look at it this way; If you have a buffer at the beginning, and you have nothing but true bypass pedals, AND they are all bypassed – then yes; a buffer will prevent any signal loading caused by the cabling. But if even ONE of those pedals is on, then IT now has the responsibility for the tone from that point onward. The buffer only makes the signal low impedance up to the point of the next active device! Besides, a good majority of the pedals out there are fairly low impedance output anyway. I think the best way to deal with this is to keep the losses to a minimum by using GOOD cables and patch cables. And imo, every pedal board should have a “B.A.T.S” box anyway. (that stands for Bypass ALL That Shit) just in case something in the chain fails, power supply craps out, etc. It’s a nice little Plan B to have in place – cheap insurance if you don’t have a guitar tech manning your devices at all times.
So here are a few ideas for making your own buffer pedal using the Area 51 Buffer kit:
NOTE: Where an LED is used, I typically use a "superbright" LED with a fairly large resistor in series with the cathode - usually in the 15K neighborhood. Whatever value gives you the brightness you want without drawing too much current is fine. The popular blue LEDs are so bright, they'll make you see spots anyway - so a big current limiting resistor is a good way to go.
The simple as it gets, buffer in a box. This one gets powered with your 9vdc pedalboad power supply, via the 2.1mm dc jack. It has input and output jacks – that’s it. The buffer board has a little trim pot for the output volume (all the way up is unity-gain). For most applications, you’re going to leave it all the way up anyway. Here's a wiring diagram.
The deluxe model, with bypass switch, dc, and level knob. I'd recommend a little larger enclosure for this one - like a 1590N1 size.
The buffered volume pedal This is a great project to mod an existing older style Dunlop volume pedal or un-used wah shell. The existing pot can be used too - just remove the trimmer pot on the buffer board and fly wires to the gear driven pot. You can even add a true bypass to it if you want.
The Buffer circuit used in the above diagrams is available here.
That's my two cents on buffers. Another really good article on the subject is this one by Jack Orman - It's an oldie but a goodie. http://www.muzique.com/lab/truebypass.htm
Till next time...keep your jacks clean. - Dan
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