Other Types of Switching and Signal Relays
Welcome to your next lesson on true bypass and its derivatives. Last month, we discussed what true bypass really means and how to know if a stompbox is truly true bypass or not. I'm sure you got right to testing some of your own “true bypass" gear, only to find that not every stompbox that is labelled “true bypass" actually is. So, if it's not true bypass, then what other bypass options are there?
This is also known as “FET switching" and is widely used in Boss and Ibanez pedals. The switching is completely silent, without any clicks or pops, and both the input and output are buffered to keep the impedances constant – the signal “looks" the same to the amp, regardless of whether the pedal is active or bypassed. For a big-time manufacturer, it is more economical to include the extra components in the PCB design and control the switching via a dead-cheap tactile switch rather than installing a big, mechanical 2PDT or 3PDT switch that needs to be hand-soldered. The drawbacks to this type of switching are that a lot of components are introduced that are not needed for the effect's actual job and the pedal will not pass any signal if it loses power.
Mechanical Output Switching:
Also known as “half-assed bypass," this type of arrangement is to be avoided at all costs (unless you plan to keep the pedal active at all times – then it doesn''t matter, of course). You''ll find it in Electro-Harmonix pedals produced before 2002, MXR (original as well as modern Dunlop reissue versions), many of the Maxon “vintage" pedals, and of course in most wah pedals. You will even find this switching system in Maxon Nine Series pedals produced before 2004 – when they were (and still are) advertised as being true bypass.
In this system, the guitar input is hardwired to the effect input and only the output signal is switched. The presence of the electronics will affect the guitar signal, something you won't hear when the effect is active, but will definitely notice when it's not (especially if there are no other pedals between this pedal and your guitar). The input impedance of the effects circuit will also effectively be placed in parallel to the input impedance of the next pedal (or amp), lowering the combined input impedance to half what it should be. About the only upside to this switching system is that the bypass signal will pass through even if power is lost (an indication in itself that it is not true bypass, as you remember from last month).
Other than true bypass, Electronic Switching and Mechanical Output Switching are the only major variants out there – with minor alterations here and there, of course. For the most part, everything else is just new, exciting terminology used to boost sales. Remember to read ads with open eyes and check the terminology carefully. If a brochure says anything other than “true bypass," in that order and with no other words in between, then it is safe to assume that the switching is one of the variants. If it actually says “true bypass," it's still always better to check it out for yourself if it is important to you.
Most of the real boutique stompboxes actually are true bypass – Robert Keeley, Analog Man, Fulltone and Visual Sound, to name a few. These guys are very honest about this, and will let you know if they use something other than real true bypass for any reason. A lot of other companies, however, are very creative when it comes to this subject, and make up their own terminology. Here are some of their creations:
- Hardwire Bypass (sometimes even called “true hardwire bypass"): This only means that the switching isn't electronic. In 90% of the cases, it's the good, old, half-assed bypass with a buffer section in front to ease the signal loading. The other 10% are pretty much the same except without the buffer. For instance, MXR uses a buffer at the start of the effects circuit, which is designed to present a high enough input impedance to be “electrically transparent" – the idea being that the electrons will not even try to move that way when the bypass line is open.
I''ve even heard Dunlop techs repeatedly refer to this system as true bypass – it isn't. True bypass depends on the effects circuit being physically disconnected from the input signal in bypass mode. But does the Dunlop/MXR system (sometimes referred to as “electronic true bypass," an oxymoron if I ever heard one) work as intended? Not really; it may be as “invisible" as it wants, but it will still drop the overall input impedance the pickups “sees," compared to when it's active, thus changing the tone.
- Hardware bypass: A variant on the above, used by Hughes & Kettner. In their sales blurb, they say: "The sophisticated hardware bypass ensures the instrument signal remains 100% unaffected in the bypass position." Very interesting, but not true bypass. The wiring is actually the same as in the earlier example – they even go so far as to reference the MXR system, but stop just short of calling it true bypass: "The TUBEMAN features a real audio treat, the hardware bypass. This type of signal routing, popularized by the MXR Classics, ensures the instrument signal remains 100% true and unaffected in the bypass mode.
- True (hot-wire) bypass: I just spotted this one, and frankly I don't know what it is supposed to mean. Or rather, I know what it wants you to think it means, but I don''t know what it really means. My hunch is that it's the same as the other variants – a direct connection from input to output, but with the effects circuit still connected.
- Virtual bypass: This can be anything, really. Many times, these pedals have a round, metal stomp switch that controls the switching transistors in an electronic switching arrangement. At other times it is the same as the hardwire bypass, with a buffer to ease the loading and extra-high input impedance. Again, the theory is that once the gateway directly to the amp (via the switch) is opened, the high-input impedance of the effect will make it “invisible" to the guitar signal. It's a nice theory, but it doesn''t work in practice.
- Passive bypass: Used by Marshall, among others. I'm guessing it denotes a mechanical switching system of some sort, and I''m also guessing that it is the same output switching system as in the others. If it were really true bypass, they'd definitely want to use that term.
- Side chain: Some of the signal is tapped off to the side into a separate chain. This is the thinking behind the “tuner out" jacks on volume pedals – the signal is tapped before the volume control, so you can tune with the volume off. Also, since it is a “side chain" it doesn''t have anything to do with the main signal chain, right? Neat idea, but it doesn't quite work. Aside from the lack of a switch to select between them, that system is exactly the same as what you get when connecting your tuner to the “tuner out" on a volume pedal.
(sometimes even called “true hardwire bypass"): This only means that the switching isn't electronic. In 90% of the cases, it's the good, old, half-assed bypass with a buffer section in front to ease the signal loading. The other 10% are pretty much the same except without the buffer. For instance, MXR uses a buffer at the start of the effects circuit, which is designed to present a high enough input impedance to be “electrically transparent" – the idea being that the electrons will not even try to move that way when the bypass line is open. I''ve even heard Dunlop techs repeatedly refer to this system as true bypass – it isn't. True bypass depends on the effects circuit being physically disconnected from the input signal in bypass mode. But does the Dunlop/MXR system (sometimes referred to as “electronic true bypass," an oxymoron if I ever heard one) work as intended? Not really; it may be as “invisible" as it wants, but it will still drop the overall input impedance the pickups “sees," compared to when it's active, thus changing the tone.
So remember, true bypass means that the circuit is physically disconnected from the input jack/bypass line. If a pedal doesn't do this, it is not true bypass – period!
Next month we will talk about how you can easily build your own true bypass box or strip and I will show you a very easy, yet effective buffer circuit – also an excellent beginner's DIY project. Don't forget to heat up your soldering irons because next month we will convert your effects rig into a pure, true bypass setup for only a few bucks.
Dirk Wacker has been addicted to all kinds of guitars since the age of 5 and is fascinated by anything that has something to do with old Fender guitars and amps. He hates short scales and Telecaster neck pickups, but loves twang. In his spare time he plays country, rockabilly, surf and Nashville styles in several bands, works as a studio musician and writes for several guitar mags. He is also a hardcore DIY guy for guitars, amps and stompboxes and also runs an extensive webpage singlecoil.com about these things.