Sunday 14 February 2010

PNP Germanium Buffer



Slightly modified values giving greater input impedance and resulting in a slightly brighter tone:

10 comments:

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    1. I doesn't really matter. This is an emitter follower which is always around unity gain for the stage, no matter what the individual current gain of the transistor.

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  2. Looks like my leaky m40a ge have a use after all. Mark great recommendation on the dc55 semiconductor analyzer! It is awesome. I am officially a lazy transistor tester now. Well I guess I was before, to be honest, because I just did not test them.

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    1. Yes I don't know how I ever got on without one. It's worth having one just so you can connect up any transistor and get the pinout to save you having to check the datasheets every time

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  3. Hi, two questions about this buffer. Regarding the first comment I think that the hfe should be important since higher hfe means higher imput impedance and at the same time lower output impedance. This is what I could figure out from the general common collector equations, am I wrong?. And second one: if this pedal is built without led and without switch (meaning is always on) then the two 1M resistors could be deleted from the layout? I ask this because I am assuming both are pulldown resistors
    thanks

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  4. So is this a Negative power? do i need to use voltage converter?

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  5. is that vero board? what do you mean by negative power?

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    Replies
    1. It's tagboard. Google it :)

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    2. For the negative power question, most of these effects have a 9V supply and 0V ground. Ground is a lower potential than supply and so it's referred to as a negative ground. Some circuits, particularly some older germanium fuzz pedals, require a -9V supply and 0V ground, and these are referred to as positive ground circuits. The wiring always show the correct way for the particular effect to be wired and the only concern for you really is that positive and negative ground effects aren't daisy chained using the same non-isolated power supply because you'll almost certainly destroy it. So you need to use separate lines of an isolated PS or maybe two separate non isolated PS's, one for positive and one for negative effects,

      http://tagboardeffects.blogspot.co.uk/2014/08/negative-and-positive-ground-effects.html

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  6. Hello, I find this to be slightly dark, is that possible? I believe that being a buffer should be exactly the opposite, or maybe I wired it the wrong way? I have used stripboard and I converted the above layout resulting in this (in case someone finds it useful)

    https://www.dropbox.com/s/2cqv8idpa4yj29f/pnp%20buff%20stripboard.png?dl=0

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