Looking at parts and knowing what to do with them

Question

I want to make an audio amplifier. I, of course, looked it up on youtube but I do not have all the parts however I do have a lot of parts. I have a lot of boards I have ripped parts off of. I am curious to how do I just look at a pile of parts and know what to use and how to use them to make an audio amplifier or anything else? I know people do this all the time but I have no clue how.

jw0752 · Answer

Hi Justin, There is no magic path to knowledge. I would recommend that you pick individual components that you have and then build something simple around that component. Data sheets often offer sample circuit suggestions that are a good place to start and offer a simple way to become more familiar with the part. As you build familiarity with parts you will find that you will reach back and find uses for what you have learned as you build future projects. Your salvage parts can serve as a resource but you will seldom be able to rely only on them completely for completion of a specific project. I always have to laugh when I watch Star Trek and everyone seems to be able to build an interstellar communicator by hooking random pieces of technology together.This is seldom the way the real world works. Make it fun to learn and embrace the challenges. We are all just like you though, we may be at different positions on the path to knowledge and experience. Go back and read the suggestions of DAB , 14rhb , fmilburn , and genebren as they have each given good insights as to where to continue your journey as it sounds like you have already begun by collecting assorted parts. John

fmilburn · Answer

I suggest starting simple - e.g. a single transistor amplifier. Also, try a good book or if you prefer the internet for a write-up of how transistors work rather than YouTube. Here is an example (which I have not tried but there are many others): https://www.hackster.io/jwzumwalt/single-transistor-audio-amp-32033a

When you understand how the amplifier works then try to build something similar. Many common transistors should work. The link above has the math for selecting caps and resistors. If you don’t have the exact part then subtitute what you have. Swap out parts and see how that changes things. You don’t need anything other than a transistor, battery, capacitor, and a couple of resistors to get started. If you have problems then forums are a great place for help but I am guessing you can get something working pretty quickly and then start looking at ways to improve.

stevenselder · Answer

For a start, Take an OLDER Transistor Radio & Follow The Speaker Circuit back . The LARGE Boom Box or Cigar Box Size are easier to work with. You can use the entire PCB or cut off the R/F parts to save space. You can also use an old Tape CC Recorder PCB. Set to PLAY input would be tape head leads. If TOO MUCH gain, move in a Transistor or 2. Use series capacitor to block D.C. This "Reverse Engineering" will also assist you in Parts Identification. It also assures the parts are designed for audio use. Good Luck

DAB · Answer

Hi Justin, Your question highlights the advantage of an education in Electronics Engineering. With that education comes an knowledge of the existing electronic components and how to properly put them together to make circuits to do specific functions. Having a pile of parts may or may not provide everything you need for a specific circuit, but in engineering, we learn to do "close enough" compromises on components to get working circuits with acceptable defects. So a good engineer can make design circuits in many ways to do a specific function out of a wide variety of components. A good maker can in most instances follow basic cook book circuits and then adapt them to the components at hand. You just need to understand what the compromises are and how they affect the circuit. Using a Computer Aided Design tool enables engineers and makers the ability to look at the affect of using different components for a given circuit. So if you learn how to use these tools, you can get a good idea of how to use what you have to get what you want. Just be aware that there are no magic bullets. The more you learn about electronics, the more successful you can be. After 45 years, I still learn new things about electronic components and how to use them, so there is a good reason to keep current with the changing technology. DAB

genebren · Answer

malus_lupus , Something like LTspice (or any other spice based tool set) can be very useful to experiment with circuits to see how various components interact with each other. You can take a basic amplifier design and substitute a different op-amp into the circuit to see how it works. The more you know about electronics, the easier some of this becomes, but you can develop some of that understanding by reading and following the lead of other designers. There are a lot of very interesting projects documented here on element14 that you can use to help you increase your electronics knowledge. Good luck, Gene

14rhb · Answer

Justin, If you haven't already done so then you may find it advantageous to identify some of the components you have stripped off boards, obtain the datasheet on them and also list them in an inventory. Then you could start to search the www on 'audio amplifier' plus the unique name of one of your amplifying components e.g. an IC or transistor. Rod

Fred27 · Answer

I'd start from the other end. Find a circuit you want to build and buy the components you need. If you can include some salvage ones then that's a bonus. Parts are not particularly expensive - especially when compared to your time and the effort you put into learning electronics. The pile of component you have in front of you are probably worth pennies. Don't attach too much importance to that.