Hey folks -
From what I've noticed, a lot of the amp builds around here are simply done from existing schematics or kits, and while I can follow directions easily, I'm having a little bit of difficulty figuring out exactly why things work the way they do. I've yet to see a writeup that explains, step-by-step, what the circuit is doing, and how one goes from building a very simple amp to a more complex amp. I don't know enough of the theory to know how to go from one to the other.
I'd prefer to have an understanding of what's going on. I've got a truck-load of components at my disposal, and rather than buy a kit or more parts, I'd just as soon dig through my box of power-transistors power-supplies, and passive components and throw something together... but I don't know exactly how to start.
I've just taken apart a JVC stereo tuner. By itself, I know that it's an audio amplifier -- a dual-channel 220watt amp that puts out a decent amount of sound. I'm in the process of scavenging parts off of it, because the panel (all the buttons) is defective, and rather than fix it, I'd rather learn on it.
The JVC uses two sets of power-transistors: a pair of 2SB1429 and a pair of 2SD2155. Using those transistors and the power supply that's in the JVC, how would I go about building the a simple audio amplifier? Or a moderately complex amplifier?
Thanks in advance. I ask a lot of questions, so please be patient with me.
From what I've noticed, a lot of the amp builds around here are simply done from existing schematics or kits, and while I can follow directions easily, I'm having a little bit of difficulty figuring out exactly why things work the way they do. I've yet to see a writeup that explains, step-by-step, what the circuit is doing, and how one goes from building a very simple amp to a more complex amp. I don't know enough of the theory to know how to go from one to the other.
I'd prefer to have an understanding of what's going on. I've got a truck-load of components at my disposal, and rather than buy a kit or more parts, I'd just as soon dig through my box of power-transistors power-supplies, and passive components and throw something together... but I don't know exactly how to start.
I've just taken apart a JVC stereo tuner. By itself, I know that it's an audio amplifier -- a dual-channel 220watt amp that puts out a decent amount of sound. I'm in the process of scavenging parts off of it, because the panel (all the buttons) is defective, and rather than fix it, I'd rather learn on it.
The JVC uses two sets of power-transistors: a pair of 2SB1429 and a pair of 2SD2155. Using those transistors and the power supply that's in the JVC, how would I go about building the a simple audio amplifier? Or a moderately complex amplifier?
Thanks in advance. I ask a lot of questions, so please be patient with me.
Wow, going straight to a jog without taking baby steps or walking. You are brave. I would suggest a google search for some tutorials on electronics theory, they are out there, this will help you understand how things work, thus how you can use the parts you have to design an amp. I would suggest using one of the designs already available for your first project, with the necessary mods to accommodate the components you have.
Peace,
Dave
Peace,
Dave
CBS240 said:
That's a fascinating question. I think my objective is really less about meeting a particular specification, and more about understanding transistor-based audio amplifiers.
I liken it to this: Let's say you want to know how to build an outdoor playhouse. You could start with questions like "how many square feet do you want it to be?" "How tall do you want it to be?" etc., etc., but in reality, those questions are unnecessary to know *how* to build a playhouse. Building a playhouse is, in the most basic sense, a matter of a floor, walls, ports, and a roof. The specifications are only useful for finishing the work; they're not necessary to gain a basic understanding of the construction.
The understanding of the construction of transistor-based audio amplifiers is really what I'm shooting for. I've read up on what a transistor does, what an op-amp does, what resistors and capacitors do, etc., etc., but I don't have a good visual concept for what's going on with an audio signal as it goes from input to output.
I've built a couple of LM386-based mini-amps, and like I said -- I can follow instructions. And I could follow instructions for a transistor-based amp as well, but it doesn't help me gain any ground in understanding what's going on, and it doesn't allow me to expand on the circuit, or improvise. But that's exactly what I want to learn to do.
Hello J_C, I am trying to figure out a way to explain how the pieces go together, but I must confess that I've never tried this before, so it isn't easy. It is much easier to explain something like how an amp works when you have a schematic to look at and reference. It is another thing when you have to imagine general concepts and then translate those concepts to language that newbies will understand. I will think about this and try to get back to you. If no one else of greater knowledge than I comes along and helps you out, please drop another comment to remind me.
Peace,
Dave
Peace,
Dave
Several more or less random points:
--Find a copy of Horowitz & Hill's The Art of Electronics
It's not enough to know the dictionary definition of the parts. You have to figure out how they act and interact. Unfortunately, things are a little more complex than applying a hammer to a nail to bind one piece of wood to another.
--If it's simple amps and rationale you want then hie thyself hence to www.passdiy.com and start reading the sundry construction articles. The circuits range from one notch above trivial to moderately complex, with multiple stopping points in between. And a lot of explanations along the way. Think Suzuki method: Learn to play, then go back and add theory.
--Some of this is just gut feeling. It's one thing to be able to say that you know Ohm's Law. It's another entirely to look at a a schematic and say, "Wait a minute...something's not right, here..." Experience takes time.
--If it were easy, everybody would be doing it. The fact that they're not--and that even a lot of the ones who claim they're doing it aren't doing it well (think of a kid running across the front yard holding a board as a wing..."Lookit me! I'm flyin'!"...in their minds, they're flying, in reality they have yet to leave the ground) is just part of the process.
--Don't let anything dissuade you if you are truly serious. Just don't expect miracles. The trick is not to get so serious that you burn out in six months. Play with it so that it's fun and you'll last a whole lot longer. Try a couple of simple to moderate projects first so that you have background music while you're designing your Magnum Opus.
--Sooner or later, someone will suggest that you simulate rather than build your circuit. I'll put it this way...there are inflatable sex dolls and there are real women. Once may get you through the night. The other might become a lifelong companion. Ask yourself which you would prefer.
--I myself tend towards vertical learning curves. About every two to five years, I attack something new. Right now I'm learning to make sausage. I've yet to make a bad one, but the ones I'm making now are a damn sight better than the first ones I made. I'm honest enough to admit that I'm not ready to win awards, but I'm also far enough along that we no longer have to buy sausage at the store. If you approach audio with reasonable expectations, relative to your own abilities, you'll have something to occupy many a midnight hour from here on 'till you go deaf in your old age.
Grey
--Find a copy of Horowitz & Hill's The Art of Electronics
It's not enough to know the dictionary definition of the parts. You have to figure out how they act and interact. Unfortunately, things are a little more complex than applying a hammer to a nail to bind one piece of wood to another.
--If it's simple amps and rationale you want then hie thyself hence to www.passdiy.com and start reading the sundry construction articles. The circuits range from one notch above trivial to moderately complex, with multiple stopping points in between. And a lot of explanations along the way. Think Suzuki method: Learn to play, then go back and add theory.
--Some of this is just gut feeling. It's one thing to be able to say that you know Ohm's Law. It's another entirely to look at a a schematic and say, "Wait a minute...something's not right, here..." Experience takes time.
--If it were easy, everybody would be doing it. The fact that they're not--and that even a lot of the ones who claim they're doing it aren't doing it well (think of a kid running across the front yard holding a board as a wing..."Lookit me! I'm flyin'!"...in their minds, they're flying, in reality they have yet to leave the ground) is just part of the process.
--Don't let anything dissuade you if you are truly serious. Just don't expect miracles. The trick is not to get so serious that you burn out in six months. Play with it so that it's fun and you'll last a whole lot longer. Try a couple of simple to moderate projects first so that you have background music while you're designing your Magnum Opus.
--Sooner or later, someone will suggest that you simulate rather than build your circuit. I'll put it this way...there are inflatable sex dolls and there are real women. Once may get you through the night. The other might become a lifelong companion. Ask yourself which you would prefer.
--I myself tend towards vertical learning curves. About every two to five years, I attack something new. Right now I'm learning to make sausage. I've yet to make a bad one, but the ones I'm making now are a damn sight better than the first ones I made. I'm honest enough to admit that I'm not ready to win awards, but I'm also far enough along that we no longer have to buy sausage at the store. If you approach audio with reasonable expectations, relative to your own abilities, you'll have something to occupy many a midnight hour from here on 'till you go deaf in your old age.
Grey
Ok - topography.
I've read a few dozen articles, glimpsed through a few books, and I think I have a better understanding of what's going on. I've got an idea of how the math works, in terms of biasing the resistors and all that.
As far as a class A amplifier goes, is that really all that's required? You figure out your input voltage, your power voltage, your desired gain, and apply appropriate transistor/resistor combination, and voila?
All the information I have seems to point that way, but I feel like I'm still missing a step or two. Any other thoughts?
I've read a few dozen articles, glimpsed through a few books, and I think I have a better understanding of what's going on. I've got an idea of how the math works, in terms of biasing the resistors and all that.
As far as a class A amplifier goes, is that really all that's required? You figure out your input voltage, your power voltage, your desired gain, and apply appropriate transistor/resistor combination, and voila?
All the information I have seems to point that way, but I feel like I'm still missing a step or two. Any other thoughts?
Well if you have already a working understanding of basic topologies you could start to either build circuits, measure their performance and listen to them and/or do simulations. If you don't have the cash for equipment (or lack of space, or don't want to buy that stuff yet) - you can still learn a lot by simulating circuits just by trying to get correct results*. However you must now at least the dc-working points including gain, bandwidth, distortion at a certain power level before the simulation, so better sim a known circuit first (Pass Aleph 30 is an excellent start!).
Have fun, Hannes
*LTSpice is for free.
Have fun, Hannes
*LTSpice is for free.
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