Let‚Äôs 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‚Äôs your chance to ask an engineer, in our new blog series called ‚ÄúAsk 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‚Äôre 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‚Äôs a summary of the bypass terms we use and what they mean:
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‚Äôs in the way between your guitar and the amplifier, the cleaner the signal will be. When we say ‚Äúclean‚ÄĚ we usually mean free from high frequency signal loss. Be careful though‚ÄĒif 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.
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…
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.
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.
Instead of using a mechanical switch to bypass, we can use a device called a ‚Äėrelay.‚Äô 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‚Äôs 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.
Now that you know all the terms, I present to you, the official Dunlop Bypass guide!
DUNLOP BYPASS GUIDE
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