• on Audio/Video/Photography
  • Published in issue 7/2010 on page 87
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Glass Blower

(Summer Circuits 2010 article)

Glass Blower

Most guitar pedals obtain a high input impedance simply by using a large resistor at the input of the first opamp, but this generates a good deal of noise due to the input bias current. The Glass Blower avoids this by using a smaller resistance (R2) which is bootstrapped by C2 to an effective value of tens of megohms.

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Extra info, Update

Correction

September 22, 2010.

On the component layout of the PCB designed by the author (free download # 100165-11.zip), transistor Q2 (2N3906) should be turned 180 degrees.

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