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I'm currently building a very simple overdrive/distortion pedal using a 2N5089 transistor.

I want to be able to have a potentiometer control the "drive" which I assume is the voltage amplification. Do I do this by changing the base current?

Hopefully this isn't a stupid question and I appreciate all responses and any guidance in learning more and more about electronics in this area.

Thank you in advance

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closed as unclear what you're asking by Asmyldof, uint128_t, PeterJ, Bimpelrekkie, Rev1.0 Apr 5 '16 at 7:08

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Welcome to EE.SE where schematics are the language we all speak. There's a schematic button on the editor toolbar. If you're using an existing design then paste in an image of the schematic and a link to the text. \$\endgroup\$ – Transistor Apr 4 '16 at 19:17
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    \$\begingroup\$ There's no circuit so we cannot comment on anything unfortunately. Usually you do not change the base current to change the gain. You can avoid asking a stupid question by doing some homework like: have a look at similar circuits on the internet, try to figure out how they work etc. Learn some electronics basics. Learn that telling us that you use a 2N5089 is the same as telling us your bike has 2 wheels: irrelevant to the question. If that's too much trouble to learn all that that's fine but then get a ready-made design and build that. \$\endgroup\$ – Bimpelrekkie Apr 4 '16 at 19:18
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    \$\begingroup\$ @FakeMoustache lets turn down the patronizing please. \$\endgroup\$ – Passerby Apr 4 '16 at 20:02
  • \$\begingroup\$ @Passe: No, you turn down your misplaced do-gooderness. FakeMoustache was right on. \$\endgroup\$ – Olin Lathrop Apr 4 '16 at 20:16
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    \$\begingroup\$ @PatricoFerris as has been said, a good place to start learning is by looking at similar circuits on the internet. The website listed below has schematic diagrams of lots of well known guitar effects pedals. Start by trying to understand how they work. You could even build one or two. Then figure out how to modify them. Then you may be able to design one yourself. generalguitargadgets.com/how-to-build-it/technical-help/… \$\endgroup\$ – Steve G Apr 4 '16 at 20:48
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The typical way to get variable gain, like a volume control is to put a potentiometer in front of a fixed-gain amplifier. Set the amplifier to the maximum gain you ever want, then use the pot to scale down the input signal you feed into the amp.

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  • \$\begingroup\$ Thank you for the quick response, I appreciate all of the help people give. \$\endgroup\$ – PatricoFerris Apr 4 '16 at 20:10
  • \$\begingroup\$ I'd put the potentiometer on the output of the fixed-gain amplifier in order to reduce noise contribution to the input signal. \$\endgroup\$ – HarryH Jun 9 '18 at 18:12
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    \$\begingroup\$ @Harry: That's not usually good. Lould signals will then clip the amp, even though they would have been attenuated by the volume control later. For a single-stage amp, just put the volume control before it. For a multi-stage amp, you can put the volume control on a intermediate signal that isn't as sensitive to noise. But, you still have to make sure that intermediate signal will not clip with the maximum valid input. \$\endgroup\$ – Olin Lathrop Jun 9 '18 at 21:20

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