I am wanting to design, prototype, and build a very simple circuit that will take a 3.5mm headphone jack as an input, amplify the signal (hi gain, very low distortion), and output the signal via another 3.5mm jack where I could connect my headphones or speakers.

Disclaimer: I have dabbled with electronics, circuits, and digital logic for years and I love making things with embedded systems (Arduino, Spark/Particle Core, BeagleBone) and the hardware side is extremely simplistic but I will be the first to say (I can't emphasize this enough), I am not an EE. My saying I'm an engineer is equivalent to a high school student taking an algebra class and telling everyone s/he is a mathematician. I just want everyone to see that and understand in hopes that I might be assisted rather than crucified for asking for help. I'm not asking for anyone to do it for me, but to just point me in the right direction.

Because I build a lot of projects and I prototype quite frequently, I have a good number of common components. From what I gather from research and experience, I would imagine I have all of the necessary parts to accomplish this.

I figured I could use a capacitor and resistor to filter certain frequencies (not extremely specific but mostly unwanted and undesirable frequencies). I would take the base of a transistor and connect it to the input signal and use that to modulate a separate circuit that is connected to power and the collector-emitter of the transistor. From there, it can be filtered again and then goes to the output jack. Is that a correct understanding of how it would be laid out? If not, what am I missing? Is there a better or easier way of doing this?

I have several 2N2222 transistors, countless capacitors, and even more resistors. I also assume a potentiometer will need to be added to the output circuit to control volume.

Some of the schematics I've seen online use what appears to be an op amp (or another IC but I don't know the exact function it performs) and I'm not too knowledgeable with those (I have a few on hand, though).

I would like to know if my idea a valid and plausible solution or if I should make some changes. Also, is there a relatively simple way to determine the correct resistor and capacitor values? Will I need an external power source (I don't think transistor can source but I could be wrong)?

I'm open to all constructive criticisms, opinions, or suggestions. Please, don't say anything if all you can think of is "read a book" or "take a class". There are a myriad of people that have gotten into this as a hobby and don't have expert-level engineering experience or knowledge, so I know others may find the answer provided useful.



closed as too broad by Daniel Grillo, Voltage Spike, ThreePhaseEel, Peter Smith, rdtsc Nov 22 '16 at 12:37

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. 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.

  • \$\begingroup\$ Look, get rid of all the BS in the question because all we need to know is that you are a noob to be able to aim answers at the right level. You also need to state if learning is your main objective or just finding a solution. If it's just finding a solution then follow Richard Crowley's advice in his answer. To design an amplifier you need to know maximum input signal level, frequency response, gain, output load impedance and power supply available. You need to state those. \$\endgroup\$ – Andy aka Nov 18 '16 at 10:17
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    \$\begingroup\$ electronics.stackexchange.com/help/how-to-ask \$\endgroup\$ – Voltage Spike Nov 18 '16 at 16:46

Go to Ebay and look for headphone amp kits. There are many to choose from and they will include all the proper parts, etc. There appear to be some nice examples less than US$10 with free shipping.

  • \$\begingroup\$ Or google Simple Transistor Amplifier to find thousands of schematics and articles, such as this one. It isn't too difficult to find one which outlines everything needed to understand how to design one. Good luck. :) \$\endgroup\$ – rdtsc Nov 22 '16 at 12:33

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