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BUILD NOTES

Bypassing the true bypass / buffer switch

The E-Switch EG4208 slide switch used for the true bypass/buffer selector is available from Mouser

Electronics but may not be accessible to everyone. If you are unable to obtain it, you can hard-wire the

switch to either true bypass mode or buffered mode by soldering jumpers to the switch pads.

Transistor substitutions

The BC549C and BC550C are interchangeable with no difference in sound, so either can be used. If you

want to substitute a different transistor, you'll want one with very high hFE, in the 600s.

The PCB layout uses the B-C-E transistor pinout, which is the opposite of the E-B-C convention used by

transistors with a "2N" prefix such as the 2N3904. The closest substitute in this series is the 2N5089. If

using these, rotate them 180 degrees. Use a multimeter to check the pinout if you're not sure.

The transistor outlines also include a rectangular collector pad above the "B" and "E" pins so that a SMD

transistor such as the BC849C can be used.

Z1 zener/reference voltage

Z1 (LM4040DIZ-5.0) is a micropower zener diode in a TO-92 transistor package, intended for high-

precision voltage references at low operating currents. Accordingly, the bias resistors (R21-23 and the

Bias pot) are a lot larger than you'd expect.

These micropower types are designed to be extremely stable at low currents and they do not need a

filter capacitor according to the datasheet. If Z1 was a standard zener diode, it would likely not drop its

full 5V voltage and would be noisy or unstable without a filter capacitor.

The LM4040 is the only part that will work properly without circuit modifications. The tolerance grade

suffix (A = 0.1%, B = 0.2%, C = 0.5%, or D = 1%) is unimportant, so you can substitute whichever type is

easiest to find as long as it's 5.0V. The traced NG-3 used the LM4040DIZ-5.0, which is the cheapest type,

but the CIZ has been used in the Cornish OC-1.

NYSIAD SILICON FUZZ