I’ve seen a lot of misinformation written about true bypass switching, and little of it is confirmed by the actual measurements that I have made on the currently available switches and multiple pedal setups.
The modern DPDT and 3PDT switches used for bypass switching in pedals were specifically designed for audio use and are not old sewing machine switches. I measured the capacitance between poles of two types of footswitches (dpdt and 3pdt) and could not measure ANY capacitance to a resolution of 0.001nF (+/- 2pF). Also, the contacts of the footswitches used currently have a resistance of less than 50 milliohms (0.05 ohms), and may even be silvered for better performance.
The actual measurements of a string of true bypass pedals with one-foot interconnects show that there are minimal changes in series resistance, capacitance or inductance that could have an influence on the sound. The quality of cable used between the guitar and the pedalboard will be much more critical to maintaining the original guitar tone.
What about buffered pedals? Let’s say you are a Boss pedal user and have a BD-2 Blues Driver, AC-2, CE-2 chorus and a DM-3 echo in your pedal chain.
With all pedals bypassed, you have 3 transistor buffers active in the BD, 2 transistor buffers in the AC, 1 transistor buffer and 2 opamp buffers in the CE, and 2 transistor buffers and 2 opamp buffers in the DM!!!!
To summarize: that is 8 transistor buffers and 4 opamp buffers in your signal path at all times, even when none of the pedals are being used! There are also 4 jfet switches in the signal path and the opamp circuits are doing a pre/de-emphasis in the CE and DM. And that is only with 4 pedals; not an extreme example.
I guarantee all of this will have an impact on the sound that even the most tin-ear will be able to discern.
Every electronic circuit that you insert in a signal path adds some noise. They also add a bit of distortion and possibly some hi-freq loss. If you say that each buffer adds 1db of noise (and it is more than that with the cheap transistor buffers and opamps) then the 4 pedal example that I used has 12db more noise than the straight signal.
This doesn’t mean that buffers are bad - on the contrary, they have important uses. However, stacking a series of buffered pedals can lead to signal degradation… in the end, let your ears be the guide!
Some digital effects do not even have a real bypass; they process the signal even when the effect is switched out. The input signal is sent to the analog-to-digital converter and then straight to the digital-to-analog converter and on to the output. Even in bypass mode, the signal in the digital bypass is always subject to the limitations of the A/D to D/A conversion process including bit depth errors, distortion, Nyquist limits and conversion delays. That’s certainly not better than a couple of pieces of wire going through a 50 milliohm switch!
The easiest test is to make a simple bypass box and bypass the entire pedal chain so that you have either the straight signal through the bypass box or the buffered signal through the pedal chain with all of them switched to bypass. You should be able to hear a difference… if it sounds okay then use the chain of pedals, if you perceive a tone loss that is unacceptable, then consider alternatives.
Buy a pedal for its sound… not its bypass switch!