The Vertex Dual Buffer sports separate input and output buffer circuits, each designed for its specific task. Photo courtesy of Vertex Effects What could be better than having “true”

The Vertex Dual Buffer sports separate input and output buffer circuits, each designed for its specific task. Photo courtesy of Vertex Effects

What could be better than having “true” bypass in your pedal? This sounds like an indisputably good idea, but in fact, it’s not that simple. The subject has been written about before, but there is such confusion regarding true bypass that it’s helpful to revisit it from time to time. When it comes to preserving optimum tone, how you bypass and wire your pedals can be as important as how you power your pedal. (For more on this topic, see “Powering Your Board” in the December 2011 issue.) Let’s take a look at how both true bypass and buffered bypass work.

The idea of true bypass is that when your pedal or effect is off, there are no electronic components whatsoever touching— and thereby having an influence on—your guitar signal. This sounds great in theory, but there are some practical problems with the approach. In almost all cases, guitar pickups are passive, high-impedance devices with a relatively wimpy ability to drive a signal. Think of it as a trickling stream of water rather than a pressurized pipe. It’s very easy to divert a trickling stream with a few small rocks, but not so easy to place those rocks in a high pressure pipe without them simply being blown out.

Because the signal coming out of a guitar is weak and easily influenced, even the wire in your cables and true-bypass circuits can degrade your tone. The degradation you may hear will manifest itself as a loss of high frequencies—or “tone suck,” as many refer to it. This is caused when a simple low-pass (treble cut) filter is created with a passive RC circuit. The “R”, or resistor, is the combined resistance of all the cabling in your rig. The “C”, or capacitor, is the inherent capacitance present in shielded cables. Each true-bypass circuit adds unbuffered cable length—and therefore more resistance and capacitance to the signal path—so they create an unintentional low-pass filter.

Another problem is that the 3PDT footswitches commonly used in true-bypass circuits are not optimized to switch low-voltage signals like guitar pickups. The side effect of this can be noise or pops when switching in and out of bypass. The physical distance between the input and output jacks and the switch can also exacerbate this switching noise, in addition to adding internal cable length. A better way to accomplish true bypass is to use a relay that’s optimized for switching small signals. Such relays can be quieter and placed in an optimum location in the pedal that minimizes cable length when the pedal is bypassed.

The other way that pedal manufacturers implement bypass circuits is, of course, with solid-state electronics. This is often done with FET switching circuits and is called buffered bypass or analog bypass. A simple truth that escapes many is that any pedal with active electronics in it automatically and by its very nature will include a buffer.

Now, the quality of that buffer can vary greatly from manufacturer to manufacturer, but when buffered bypass is done well, it can be a very good method of bypassing a pedal. It provides a robust and relatively silent form of switching. Buffered bypass has simply gotten a bad name over the years because of poorly designed buffered bypass circuits that color your tone.

Because of this, and for fear of any extraneous electronics hanging on to their guitar signals when bypassed, many players insist on only using pedals with true bypass. Players who use batteries in their pedals also have to worry that once the battery dies, not even the dry-bypass signal will pass through the pedal because it requires power to do so. One drawback of buffered-bypass circuits is that pedals not using low-noise components and designs can add a significant amount of white noise to the signal chain even when the pedal is bypassed. This can usually be minimized with a correctly designed bypass circuit.

So, what’s a pedal junkie to do? There is, in fact, a best-of-both-worlds solution: Place a good quality buffer at the beginning of your pedalboard signal chain. This can be in the form of a compact dedicated buffer, a clean boost set to unity gain, or even a pedal with a high-quality integrated buffer that you don’t mind leaving on all the time.

In my personal rig, I leave an optical compressor set to a very light compression level on all the time, and it serves as my up-front buffer. What the buffer does is transform the trickling stream that is your guitar signal into a pressurized fire hose of a low-impedance signal. This significantly minimizes any degradation that can be caused by having many true-bypass pedals or lots of cable in your rig.

Having a buffer up front becomes extremely important when using a true-bypass “looper,” a device that bypasses effects externally with multiple true-bypass effects loops. In practice, those devices add a ton of extra cable to your rig. Again, a buffer up front will minimize any harm they can potentially do and let you take full advantage of true bypass. In short, put a buffer first in the chain, trust your ears, and rid yourself of bypass anxiety. Happy shredding!

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There are three major issues to consider when thinking about powering your pedalboard: voltage, current, and isolation.

With so many cool and interesting pedals readily available to the modern musician, you will inevitably come to the point where you need to build a pedalboard (especially if you’re a gear junkie like me). You’ll need to decide which kind of board to buy or build, which pedals will actually make it on your board, the optimum order of the effects, cable lengths, and whether or not you will buy pre-made cabling or wire your own. But probably the single most critical decision you’ll make is how to power all of the pedals on your new board. There are three major issues to consider when thinking about powering your pedalboard: voltage, current, and isolation.

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The architecture of a basic DSP system. Digital. The very mention of the word causes many guitarists to wince, conjuring memories of harsh, inspiration-crushing tone from early rack gear

The architecture of a basic DSP system.

Digital. The very mention of the word causes many guitarists to wince, conjuring memories of harsh, inspiration-crushing tone from early rack gear and floor-based multi-effectors. The common misconception that everything digital somehow sounds cold and sterile isn’t entirely unfounded. Back in the early days of digital signal processing (DSP), processing power was extremely limited. Early digital audio systems suffered from low sample rates and bit depths, poor dynamic range, and harsh clipping characteristics. The result was that many digital effects designers were forced to use creative tricks and compromises to overcome the limitations of their early digital systems. Whether it was a flanger, reverb, or distortion, the tone was often less than stellar compared to the vintage effects we all knew and loved. And so, over the years analog gear and effects have gained a fondness in our minds—a sort of pre-digital innocence and beauty. It’s analog, so it has to be better right?

Let’s take a look at some of the specs of early digital systems and their impact on audio quality. Due to a lack of sophisticated integrated circuit (IC) chips, the digital effects of the early ’80s were generally digital delay line effects—that is, delay, chorus, and flanging. These systems implemented 12-bit converters running at sample rates as low as 15 kHz. In a digital system, each bit of resolution will theoretically give you about 6 dB of dynamic range. So, a 12-bit converter would be capable of only 72 dB of dynamic range. The highest frequency that can be reproduced is half the sample rate, so that would be 7.5 kHz in a 15 kHz-sampled system. These specs are so out of line with current technology that they have earned a place as “old school” or “vintage digital.” If you’ve ever played through a bit-crusher pedal, you’ve experienced the sound of low bit depths and sample rates as a special effect.

By the late ’80s, digital effects had CD-player specs of 16 bits (yielding a 96 dB dynamic range) and a sample rate of 44.1 kHz or 48 kHz. During the same period, more advanced digital IC chips became available, allowing for implementation of multi-effects, reverbs, and nonlinear effects like digital distortion and compression. This new standard was still plagued with shortcomings, as the audio converter technology required the use of sharp “brick wall” filters that created non-linear phase distortion at the top end of the audio spectrum, resulting in subjective “listener fatigue” and “harshness.” Additionally, the processing power was still very limited for the ambitious applications being pioneered. This led to sonic compromises that manifested themselves as harsh clipping, metallic tonalities, and fuzzy or fluttering note decays.

Fortunately, we’re at the point now where we have a massive amount of processing power available and vastly better analog-to-digital (A/D) and digital-to-analog (D/A) converters capable of well above 110 dB of dynamic range. Some stompboxes now have more processing power available than early-’80s Cray supercomputers. Simply being in a digital system is no longer a limitation. On the contrary, digital systems can do things that simply aren’t possible in 100-percent analog designs. And effects that few studios could have afforded only a decade ago are now in the price range of the humble musician.

I have to admit I get frustrated seeing comments on forums like, “It sounds digital.” The truth now is that there are no inherent sonic qualities to a digital system. Digital effects, for better or worse, sound exactly how their designers have built their hardware and algorithms. If we think of a digital system as a blank canvas, a DSP engineer wields the brush, and whatever algorithm he or she writes ends up coloring your guitar tone.

Let’s take a look at the architecture of a basic DSP system: The guitar signal arrives at the input and is buffered by some kind of analog input circuitry. Then the signal is sent to an A/D converter. From that point, the signal is represented by a binary stream that can be easily processed. Usually this is done by a DSP circuit with some memory connected to it. The DSP circuit will run whatever algorithm it’s been programmed with and send the result to a D/A converter, then to the output jacks. Modern 24-bit, 192 kHz A/D and D/A converters can provide excellent signal-to-noise, THD (total harmonic distortion), and latency specs. Luckily, the problems that plagued early digital systems have become mostly a non-issue with modern converters and processors.

Digital effects are getting better all the time. Some of the digital gear currently on the market brings us closer to the old analog glory than we’ve ever been before. And some of it takes us to places never before possible with analog effects. Fear not—and happy shredding!

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