True byass question

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droptrd

droptrd

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What are the pros and cons of this? why doesnt every pedal has this?
 
Here is some reading for you from various sources, IMO true bypass is great as long as you are using a decent signal buffer some where in the beginning of the chain to combat cable capacitance.


With true bypass switching, the input impedance of the effects pedal has ZERO influence on the discussion we are undertaking. Why? The true bypass is designed and used to eliminate the effect of a pedal's input load on the signal... the pedal is completely disconnected when the switch is bypassed so the input impedance of the circuit is not relevant! It does not matter if the circuit has a high impedance like a tube amp or is a low impedance transistor load - it is not a factor with true bypass.

If any of the pedals after the buffer is a vintage design that does not have true bypass, then its input impedance is a load on the signal path that is constantly presented to the buffer whether any of the other pedals are switched in or out. The buffer might be capable of driving the load but the sound of the other pedals will likely be altered.

Also, once you engage any pedal after the buffer, the output of that pedal is then driving everything after it and not the buffer. For example, let's say the first pedal after the buffer is a new model Big Muff with true bypass. When it is engaged, the BMP is being driven by the buffer but the audio signal line after it is getting the output of the Muff, which is around 10k instead of the 100 ohms from the buffer.

A high quality buffer can be a good thing to have at the beginning of the pedalboard chain, but the only way to have a constant low impedance signal line is to have a buffer built into each stompbox. That is exactly what Boss and Ibanez (among others) have incorporated into their pedals. Each of their pedal circuits has a buffer that drives the effect output when bypassed. This ensures that the pedal presents a high impedance load to the signal path and drives the pedals after it with a low impedance output.

A problem that can be encountered is that many of these pedals have two or even three buffers that are in the signal chain even when bypassed. The simple transistor buffers have a gain less than 1 and once you begin to cascade pedals, the noise can start to add up. If each pedal adds 3 dB of noise and you have 10 of them in series, it could be increasing the noise level by 30 dB! It is never quite this bad in actual practice but the degradation of sound and the extra noise can indeed be audible.

Conclusion

The measurements that were made for this article have revealed that it is not a problem in practice to chain together numerous true bypass pedals. You really won't hear any difference if you use good quality guitar cables and jumpers. A buffer can be put to good use to drive long lines but combinations of pedals from different manufacturers can be a problem, especially if you have an old vintage pedal that is not true bypass. Having a buffer in each pedal circuit may be correct one problem while introducing noise and distortion.

The only good solution is to have a top quality opamp buffer in each pedal circuit that drives the output. This would mean that vintage pedals and many of the popular commercial devices should not be used... and that's not too practical for most players.

“A buffer is basically an active device that takes your somewhat weak guitar signal and amplifies it. Usually a gain of one – or a unity gain – is used so the volume does not change and your sound remains constant. Your signal is converted to a lower impedance so it can travel through long patch cords without losing its strength.

“A buffered pedal (for example a BOSS or Ibanez pedal that is turned off) will allow a good tone to make it through a cheap or long patch cord. Some years ago I sold several true bypass pedals to a player with a large pedalboard. He said it sounded terrible and that one of the pedals must have a problem. When he brought the board to my shop, all the pedals checked out fine. We determined that his cheap patch cord from guitar to board was killing his tone, but he never noticed it as he had previously used a few buffered pedals. Replacing the cable solved his problem and the new pedals worked great.

“There are various opinions regarding the use of a buffer in a signal chain. Some seemingly opposing opinions are given by authorities who certainly can’t be wrong, as their clients have awesome tone. Using a true bypass remote switching system or a full pedalboard of boutique pedals is one extreme, while a board full of BOSS and Ibanez pedals or a switching system with buffers on each switch is the other extreme. My belief is that buffers can be used, and should be used in some cases, but the number of buffers in your signal path should be minimized.

“A buffer is often used as the first device in a board to get the signal from your guitar into good shape early on. But this is a problem if you’re using a vintage pedal like a Fuzz Face. A germanium Fuzz Face needs to interact directly with your pickups for the magic clean-up effect to occur when you roll your volume knob down – the pickup and volume knob actually become part of the fuzz circuit. Other pedals like a germanium treble booster or Rangemaster-type pedal will sound bad if there are any buffers before them – they get bright and nasty sounding. If you have one of these pedals, put it early in your effects chain before any signal buffers or buffered pedals.

“Most players using a wah pedal prefer to place it before a fuzz in their signal chain, but a vintage wah will not behave well with a fuzz – losing its tone and sweep. Adding a buffer inside the wah will allow it to function better with the fuzz when the wah is on. Turning off the wah – with true bypass – kills the buffer so it will also work well when it’s off. Foxrox Electronics makes a wah retrofit kit, which can be added to most vintage-style or boutique wahs. Teese RMC wahs now include this ‘fuzz friendly’ buffer circuitry.

“The reason I do not like too many buffers in the signal path is that the tone changes are additive. Each one will slightly change your tone and can reduce the interaction and liveliness of your guitar strings. Even though the tone coming out of a good buffer may be very nice, passing it through multiple copies can make it a bit sour. For example, a particular buffer may have a frequency response with a nice little peak at 700Hz, but after five of these buffers the peak will be five times higher and may get annoying. Each active component also generates noise, which adds up. I have one buffer at the end of my pedalboard (a delay pedal with a nice buffered bypass) to send the signal to my amp on the rare occasion that I have no other pedals turned on. When something like an overdrive or distortion pedal is on, your signal is beefed up strong enough that no buffers are needed afterwards and a direct connection to the amp cannot be beat.

“As always, there are many variables, so it is best to do some trial and error testing with your personal rig to find the best sequence of pedals and buffers for your specific setup. If it sounds good, so should you.”

The "true bypass" function, which is promoted by some, can create dreadful problems with a system that uses many pedals. Take for instance a 15 ft guitar cable linked to ten pedals, each linked by a 2 ft cable, and then onto the amp by a 30 ft cable. If all pedals have "true bypass", and are off, then the total cable length hanging on the guitar output will be 63 ft. This will cause a huge loss of tone and signal level particularly if the guitar is a vintage type with low output and high impedance. The amp volume is then turned up and the treble control increased to compensate for the losses. The inherent background noise now increases by the amount of the gain and treble increase and is usually, in my experience, too bad for serious work. If one of the pedals is now switched on, then it's (hopefully) high input impedance (and usually low output impedance) will buffer all the output cables from the guitar and the signal level will rise due to the removal of some of the load on the pickups (i.e.: 17 ft instead of 63 ft of cable). The treble will rise and the tone and volume will not be as before. If that pedal was say a chorus or delay, devices which are usually unity gain, then your overall signal level and tone will vary each time an effect is added...not a very good idea.

Some pedals have an input impedance which is far from high in real terms; the input impedance of the vast majority of amps is 1 Megohm (one million ohms) and in my experience there are few effects pedals that have the same input impedance. A load on the guitar of less than 1 Megohm will reduce the volume and high frequency content of the pickup signal thus giving rise to complaints that "this pedal looses tone/volume" etc. Many effects I have tested have an input impedance of less than 100 Kilohms (ie: only one tenth of the amp input impedance) and cause serious signal losses in the effects chain.

There’s a lot of talk these days about “true bypass” effects pedals, and many manufacturers advertise as a major selling point the fact that they include this function. The subject isn’t entirely as clear-cut as it might seem, however, and there’s more to the issue of true bypass than a simple good/bad dichotomy. Let’s take a quick look at what “true bypass” actually means, and why it might be good for your pedal set up—and why, sometimes, it might not be.

When a manufacturer says one of its pedals is “true bypass”—also sometimes called “hard bypass” or “hard-wired”—it means that when the pedal is in the off position the un-effected guitar signal is routed directly from the pedal’s input jack to the output jack via the stomp switch, rather than flowing through some portion of the pedal’s circuit.

This would seem the normal way of doing things, but until recent years the majority of effects pedals were in fact not true bypass. Achieving true bypass is more complicated than it might seem, especially when you also want to have some form of LED status light on the pedal to show you whether the effect is on or off. Each of these functions requires a portion of the on/off stomp switch, and switches complex enough to achieve both true bypass and LED on/off functions haven’t been available until relatively recently, and are still pretty expensive parts. In the past, therefore, it was easier for manufacturers to use the simpler stomp switches available to switch a portion of the effect’s circuit on and off, while still routing the signal through part of the circuit in the “off” state. To the ears of some players this can sometimes weaken or thin out their guitar tone, even when an effect is supposedly “off,” resulting in a condition commonly referred to today as “tone sucking.” When you switch a true bypass pedal to off, on the other hand, you route the signal along its way from in jack to out jack via just a few inches of wire and terminal connections, a state that should result in a tone that is totally un-sucked and indistinguishable from the tone you get when you plug straight into the amp.

True bypass’ ability to boast reduced or non-existent tone-sucking is its major selling point, and it would therefore appear to be a universally good thing. In some cases the feature is a great virtue, sure. In others, however, a fleet of pedals that are all true bypass doesn’t always achieve the best straight-sound results.

Before true bypass became a tonehound watchword, some pedals without it routed the signal through a tone-depleting portion of the circuitry (they didn’t mean to do this, they just didn’t know better), which is most notoriously the case with vintage wah-wah pedals. Others, however, made a virtue of the fact that the signal needed to pass through part of the circuit even in the “off” state, and used a buffer stage to help maintain signal virtue whether the pedal was on or off. Put simply, a buffer is a basic preamp, although one that doesn’t add any gain to the signal, but instead coverts it from high to low impedance and gives it the “juice” to make the rest of the journey through long cable runs and complex circuitry without loss of tone or level. Done right, a buffer shouldn’t change the tone of your signal, just slap it on the butt and send it on its merry way with a little more spring in its step. This might sound like new territory, but I’m willing to bet you have encountered buffers without even knowing it. Many classic pedals contain them, including the great Ibanez Tube Screamer and Analog Delay series, all of the classic-format Boss pedals, recent pedals from Visual Sound, and others. High-end British pedal maker Roger Mayer even puts a choice of outputs in many of his new designs, giving you the option of true-bypass or buffered operation.

Typical Pedal BoardSo if true bypass is hailed these days as being so universally wonderful, why would we want a buffer in any pedal? Well, with just a few pedals on the floor and relatively short cable runs from guitar to pedals and pedals to amp, true bypass will often yield the best results. Now, consider the scenario of a pedalboard with 10 or more different pedals on it —not at all uncommon these days—a 20ft cable from guitar to pedals, and another 20ft cable from pedals to amp. Any guitar cord of 20 feet or more imposes a load on your signal that depletes the high end in particular, but is generally heard to be dulling down the overall tone slightly. Two of those can really sap your highs, then run that signal through 20 or more input and output jacks, 20 switch terminals and the contacts between them, and several inches of wiring within each unit to make the true bypass connections, and that’s a lot of tone sucking. If you own even a handful of true bypass pedals yourself, try it out: connect together as many as you can find (switched off), use a long guitar cord on either side, and check your tone. Now unplug at the amp, plug straight in with just one cord, and listen again. Hear the difference? In this scenario, the wonderful true bypass itself is depleting your tone.

Put a buffer stage toward the front of that loaded pedalboard, however, or even at the end of the chain, and the buffer makes the rest of the wiring and cable length after it “invisible” to your signal. Your tone is unlikely to travel through any crowded pedalboard totally unchanged, whether buffered or true bypass, but in most cases a buffer stage will preserve clarity and definition that improves your final overall sound. Any touring pro player with more than a pedal or two on the floor knows this all too well. Sure, they might use three racks full of true bypass pedals—and the fact is that many of the most desirable pedals made today are indeed true bypass—but you’ll find they either have a buffer or preamp to drive those long cable lengths, or they run through a custom-made switching system that has its own buffering, and which takes the pedals out of the loop when they’re not on. Otherwise, a loop switcher is a good way to simplify the routing and cut down your total wire lengths in the “off” state, although you still have your total guitar-pedals-amp cord lengths to consider.

True Bypass vs. the Buffer Zone? Not necessarily. Both can work hand-in-hand to achieve the most desirable results. Explore for yourself, see what works, and keep an open mind to tone rather than jumping feet first onto the hype wagon.

Let’s face it, not everyone has the brainpower of an electrical engineer; it can get quite tricky to navigate through the inner workings of what makes a great pedal without some guidance. Lucky for you (and us), we have a team of highly experienced and intelligent engineers that are willing to shed some light on your guitar effects questions. So here’s your chance to ask an engineer, in our new blog series called “Ask an Engineer.”

The first question we want to tackle concerns True Bypass. There is a lot of confusion about what true bypass actually is, so we’re going to clear it up for you here.

Joe Trau from Martinez, CA writes in:

What is “true bypass” and why do so many players seem to care about it? What Dunlop pedals feature it? Are there different ways to “bypass”?

Dunlop Electrical Engineer Jack Tang responds:

Yes, we do use true bypass, along with a variety of other bypassing schemes. Here’s a summary of the bypass terms we use and what they mean:


TRUE HARDWIRE

Your guitar signal never touches the input of the effect. A switch toggles your guitar signal to flow either into & out of the effect circuitry, or straight from the input jack to the output jack of the stompbox. You can use a ‘Triple Pole Double Throw’ (3PDT) switch to true hardwire bypass your signal and light an LED at the same time. You’ll usually find 3PDT switches in boutique pedals. You can do true hardwire with a ‘Double Pole Double Throw’ (DPDT) switch, but special sensing circuitry needs to be added if you want that LED too. Using a DPDT instead of 3PDT gives you more mechanical reliability and smaller size in exchange for the extra circuitry. Most of the newer Dunlop pedals have true hardwire via DPDT switch. So when the box says ‘true hardwire,’ believe us, it’s really ‘true hardwire’ even though you only see a DPDT inside!

People like to have true hardwire bypass pedals because it gives you the cleanest possible path for your bypassed signal. The less stuff that’s in the way between your guitar and the amplifier, the cleaner the signal will be. When we say “clean” we usually mean free from high frequency signal loss. Be careful though—if you have a very long chain of effects each with true hardwire bypass, you may still experience signal loss. A buffer like the M133 MicroAmp or MC401 Boost/Line Driver will help clean things up.



HARDWIRE

The pedal’s output jack is connected to a switch that toggles between effect output and your guitar signal. The guitar signal is always connected to the effect input. The input impedance is very high so you theoretically should not hear a difference. If you’ve ever plugged a strat into an old Phase 90 and set your amp to clean, you’ll know that there is in fact a difference in the form of high end loss (the extra cable length also makes it worse). It will take fewer…

CLICK HERE TO CONTINUE READING “WHAT IS TRUE BYPASS?”

hardwire bypass pedals in your chain to start drastically changing your tone. Again, a buffer at the start of the chain will help prevent high end signal loss.



BUFFERED

The signal always goes through circuitry in the effect. The signal is bypassed either through an electronic switch or through a variable gain amplifier. This bypass scheme buffers your signal into a strong, low impedance source. You’ll be able to drive longer signal chains without signal degradation. Also, electronic switching is completely silent. You won’t hear any ‘pops’ like you do with mechanical switches.

RELAY

Instead of using a mechanical switch to bypass, we can use a device called a ‘relay.’ You can think of a relay as a switch that is activated by electric current instead of mechanical force. Relays are still activated by the user stepping on the footswitch, but it’s an indirect activation. The footswitch activates circuitry that sends electric current to the relay telling it to switch. Since relays are equivalent to switches, we can use relays in True Hardwire or Hardwire configurations. Relays are great because we can control as many signals as we want with just one footswitch. The downside is they require some extra circuitry to control them.
 
wow thanks. Might take me awhile to translate all this info. Thanks dude :rock:
 

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