If I am correctly informed Boss pedals use FETs to switch the signal from bypass to active and back. From what I remember from a schematic the signal still passed about 3 FETs when in bypass. These also function as signal buffers.
Now what I have been thinking (which I do on rare occasions ). What about the quality of these FETs. In a long chain with all pedals in bypass there are still allot of FETs to pass.
Are the FETs used by BOSS "high quality" or could replacing them with Super Duper Feng Shui FETs improved the quality of the signal when the pedals are in bypass (or maybe also when active).
They use 2SK30A FET's, & typically just 1-or-2 (and in the newer pedals one on the input buffer) per pedal. Quick specs. from the datasheet N CHANNEL JUNCTION TYPE (LOW NOISE PRE-AMPLIFIER/ TONE CONTROL AMPLIFIER AND DC-AC HIGH INPUT IMPEDANCE AMPLIFIER CIRCUIT APPLICATIONS)
Also, to bypass the FETs you can "true-bypass" the pedal with a 3pDT footswitch and a modification to the jacks...that I have done in the past. However, for long chains of FX it's better (in my opinion) to use looper pedals of buffered selectors like the VooDoo Labs Ground Control Center (pricey, but cool).
On some boss pedals it's even worse. Boss has introduced some unnecessary emitter followers on the clean path that I always remove.
Look for example on the MT-2 schematic: R55, R8 and Q4 are doing really nothing. You can easily remove them and connect C4 directly to Q11. The result, 3 components less on your "clean" path.
Another one is the HM-2: R9 and Q2 can be removed.
Or R21 and Q12 on HM-3.
Or C13, R12, R16 and Q5 on BD-2.
And probably many more ...
The concept is "the buffer of the buffer of the buffer".
Bypass FET modification
Posted - 01/21/2009 : 09:36:46
). What about the quality of these FETs. In a long chain with all pedals in bypass there are still allot of FETs to pass.
