You’ve seen this argument many, many times. Hopefully, my peers who have written about this before me have convinced you that the revered 3PDT stomp switch, the “True Bypass with LED” savior is really just a bad idea. Mechanical parts fail, and they fail way before electronic components. Things wear out and its just how it works. When it comes to signal switching in electronics, electronically controlled relays present a much more robust solution than simple mechanical stomps.
So dig this, the more complicated the mechanical switch, the more moving parts it has, and the lower the mechanical life expectancy should be. The best of the best Single-Pole Carling Switches are rated at 100,000 cycles. You can bet your ass that a run-of-the mill triple-pole switch comes doesn’t even come close. Possibly within factor of 5, maybe 10 of that, meaning 10,000 cycles. Total shit. And that’s a statistical figure, with a BIG spread because in the real world, shit breaks, a lot.
Now dig, the Panasonic TQ2-5V relay used in Coldcraft products, and by many colleagues in the music business is rated at 10^8 to (10^7 minimum) cycles. That’s 10,000,000 activations, MINIMUM. The MOMENTARY single-pole switch used to activate the relay will wear out before the relay gives up on you. Unfortunately, relays can still cause switch POP, or audible clicking when used, but luckily, the same logic controls that switch the relay can be used to silence or quiet the switching action. This is the basis of our bypass system and others including the Jack Deville-designed “Clickless True Bypass” now available at Mammoth Electronics.
Now the problem of reliability has been solved, dare I say its been obliterated. However, there’s one more thing to consider, and that is Contact Voltage.
What the F is Contact Voltage?
Well, anytime there is a mechanical connection, there is a resistance present because the connection is imperfect. Maybe the surfaces are rough, possibly oxidized, corroded or just don’t make great contact. When a voltage is applied across the contact (AKA your guitar signal), the resistance creates a voltage drop across it, known as the Contact Voltage. We already know that relays are sealed from the outside dirty world (read: your dirty shoes, beer-soaked bar floors, and worse). The contacts inside the Panasonic relays are made of Ag and Au (Silver and Copper), two of the most conductive metals in town. Contact Voltages inside a relay will be very, very small, but what else is involved?
Yes, every pedal has 2 jacks, and requires 2 plugs. So lets say you have a modest pedalboard of 10 true bypass pedals. If you were in the know, and purchased effects from VFE Pedals, Dr Scientist Sounds, and the like (that includes Coldcraft…), your pedals have relay-based bypass. Minimal contact voltages inside the relays. Ok, so back to the MATH. 2 Jacks, 2 Plugs, 1 DPDT bypass connection (2 contacts), 10 pedals. That’s 80 contacts using a mechanical stomp switch!
What I am getting at here is that’s an awful lot of places where your signal can degrade. 80! It really only takes one faulty, dirty or otherwise weak connection to wreak havoc on a passive guitar signal. So lets do some more MATH. Suppose a typical mechanical connection is 10 ohms of contact resistance. 10 ohms is tiny, minuscule. No one even uses a 10 ohm resistor when building pedals because its basically a jumper.
Now dig, 80 mechanical connections X 10 ohms = 800 ohms! 800 ohms is basically 1K ohm, and that can be a big deal on a passive guitar signal. And this is all assuming there are no problem children, err, dirty, broken, intermittent contacts. And don’t even get me started if you’re using one of those fancy programmable switchers. You should just give it another factor of 2-4x.
Now for the punchline. Say you have a buffer. Doesn’t really matter if its an Op-Amp or Discrete, you just have one. A buffer is any preamp/active element that presents the guitar with an ideal input impedance (resistance) and provides a lower, more ideal output impedance for driving heavier loads. Put that buffer after the guitar, (or some where in the middle of the pedals even). The output of that buffer will have no problem handling an extra 1k ohm on its output. Hell, it was designed to do this.
Here’s a nice, tidy example of an Op-Amp based buffer. This is my Micro Buffer/Splitter design that I have been selling for almost two years as a pre-built mono buffer, or a DIY project. Personally, I think this buffer sound best AFTER all drive and fuzz pedals, but before any modulation or time-based effects. That’s just my opinion anyway, your ears may tell you otherwise. It can be configured as a splitter, mono or stereo buffer depending on how you populate the jumpers (J1, J2, etc).
There are many other interesting products out there such as the Cornish LD-2 which is a discrete, bootstrapped design, as well as the Visual Sound Pure Tone, which is another Op Amp buffer. You can read an argument from Pete Cornish against True Bypass here, and another here from Andrew Barta of Tech 21 NYC.