Instructables

Transistor Amplifier Build

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Picture of Transistor Amplifier Build
I've made a couple of these. I found the original schematic online then modified it because I did not have one of the parts the original plan calls for. My design allows the use of much more common parts. Although it uses more parts and is a bit more complicated.
 
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Step 1: The Schematic

Picture of The Schematic
Looking at a schematic is always how I decide of I want to build a circuit or not so I will present it first. I found the one I based my design off of here:

http://www.redcircuits.com/Page1.htm

Although mine isn't exactly like that one it is essentially the same topography. It sure looks simple enough doesn't it? That is why I choose to build it myself. I made my schematic because I did not have a TLE2141C Op-Amp. If you do then you can build the original and it should be easier than building mine.

IC1 and IC2 on my schematic are 15 volt regulators I used 12 volt ones. SL4 from the power supply section should power the lower voltage dual op-amp of course.


Step 2: Board

Picture of Board

I've made so many of these I'm not really so sure which is what anymore. I know I cleaned the schematic up a little before I uploaded a screen capture of it for the previous step. I'll be honest, often when I am doing an electronics project I just want something to work so I don't spend as much time as I should making my schematics as neat as I could before I move on to the next step.

Just so long as everything is hooked up you know? Sometimes I find while I am routing a board that some things aren't connected to each other too! Then I have to go back and fix that.

Anyhow the one I am including here looks pretty good to me. If anyone finds any problems then let me know and I'll see what I can't do to fix it.
Thats what those NE4558CP chips are for... I looked them up and they had to do with amplifying the reverb or something. I took apart a Peavey that was broken and found those IC's in there
ARJOON2 years ago
if you want i can design a smaller and more efficient pcb for you. so that we don't need to buy expensive large pcbs and a lot of etchant. nice tible
pfred2 (author)  ARJOON2 years ago
Post it. I'll check it out. I have to say taking all things into account my board design suits how I build. A board this big costs me about 50 cents to buy. That makes the cost a small factor all things considered.
ARJOON pfred22 years ago
yeah sure, but in some countries those pcbs may cost about 10-15 dollars to manufacture, since this ible is made facilitate lijes of people or hobbyists.
still glad that i got a reply
pfred2 (author)  ARJOON2 years ago
It sounds to me like people in some countries are getting ripped off. I'd be rioting in the streets over board prices that high!
ARJOON pfred22 years ago
what can i do. there is only one board supplier in Mauritius, so they take advantage of it. and eBuying is not recommended here for the time being. :P
pfred2 (author)  ARJOON2 years ago
Excessive exploitation seems to be a recurring theme in your country. First the Dodo, now electronics supplies. I think it is up to you to buck the trend. Take a lesson from your extinct feathered friends, it usually doesn't pay to be too passive about abuse. Gandhi got famous because it worked for him, normally it doesn't.

Get some of your geeky buddies together and toss a shipping container into the harbor or something! If you can manage to round up that many geeky friends then just start a company with them. Shipping containers are heavy, and the best you could hope for pulling off a stunt like that is getting all wet from the splash.

If there is any meaning to life it is making your dreams real. In order to do that it involves a lot of effort in your waking hours though.
mdog932 years ago
Where would i get these parts as "junk" are these parts commonly found somehwere?
pfred2 (author)  mdog932 years ago

I've learned to strip stuff that is similar to stuff I want to build, in this case old home stereos or radios come to mind. Though TVs and car stereos may have useful components as well.

As to where its found, well it is found in the corners of people's basements, maybe the bottom of their closet. Ask folks. It seems today everyone has some old electronic thing they don't want and would love to get rid of.

For experimenting the vintage stuff has more easily used parts too. So the older the better. I have no use for new SMT stuff myself, but there is always an LED or maybe a switch or something I can use so I take it as well.

The real good stuff to get is obsolete commercial stuff. That stuff has so much better parts in it than the consumer electronics. But somehow some people manage to latch onto that then decide it may be better if they got rid of it.

So ask around and keep your eyes open.
mdog93 pfred22 years ago
Yeah, i thought you might say that. I find getting hold of stuff hard and when i do get things i don't oten find useful parts case the chips are almost always surface mount components. I also have never seen any chips i recognise when taking apart electronics. Is there an easy way to identify them?or And will i find the right sort of ICs in stereos then?

Sorry, last question i promise- if i had to buy all of the parts for this project, how much would it cost roughly? Would it still be cheap?

Thanks mdog93
pfred2 (author)  mdog932 years ago
It is free for me. Now whether it would be cheap for you, if you have to ask then that suggests to me that things might not go as planned.

One of the very first electronics projects I can remember doing was when I took a cassette player and somehow managed to find the input for the amplifier section in it. I think I took a resistor from the positive and poked it around until I heard it make a loud noise or something crude like that. Then I hooked a microphone directly up to that spot and put that microphone onto a piece of scrap plywood, stretched some fishing line over it, and had me a guitar!

That was a long time ago now, and I did a lot of projects in between then and the amplifier in this article. It was when I got that to work that I figured maybe I have a knack for this sort of thing and the rest is as they say history.

Today I know I've no special talent, just a little luck and a lot of persistence.

One thing I have done for laughs is use a regular home stereo as a guitar amplifier. I think they sound a bit flat, could use some more aggressive biasing, or something, but it does work. Just working is an advantage though. With my circuit I cannot extend any real guarantees to others.

With hobby electronics it is often more about the process than the end results. That being said your process can yield impressive results sometimes.
mdog93 pfred22 years ago
Hmm i suppose you're right it'll be different for everybody. Even when it's trial answand error i like to know if what i'm doing and how i'm doing it is correct. Sometimes no way is 'correct' but i do like it to be fairly black and white. I have made a lm386n-1 mini amp before though with fairly successful results.
pfred2 (author)  mdog932 years ago
Analog circuitry has its ups and downs. Little oscilloscope humor there. Some of the best audio circuits have been complete accidents. I made an amp one night and it picked up an AM radio station. I spent the rest of the night trying to get it to tune into another station but couldn't manage to do it. I had fun trying though.

If you like things black and white digital logic may be what you're after. There it is either on or off. Analog is a whole other animal. I suppose there are theoretical ideals which are never attained, but there is a lot of fun to be had in between too!
mdog93 pfred22 years ago
Yeah, can you recommend any good digital circuis to get me started? The lm386n-1 based mini amp i made i believe was analog. Maybe i'll do some more mini amp circuits to gain some more understanding of things. I'll have a look at the parts i'd need to buy for this, see what it would cost.
pfred2 (author)  mdog932 years ago
An LM386 is an analog operational amplifier.

One thing I regret omitting in my article was outlining the subsections of the circuit. I think being able to grasp this is important to understanding a circuit. Then those circuit snippets can be handled in an intelligent fashion. What that also means is entire circuits do not, and often should not be built all at once. So I'll do that now and it may help you in reading my schematic, others too.

I'm probably not 100% correct with this but hopefully you'll get the idea and look at circuits as sums of their parts. Better than looking at schematics as big confusing mazes. Though they are that too.

Making the sub section block leap was a big step for me comprehending electronics. Everything is digestible if I break it down into manageable bite sized chunks. Put another way big jobs are more easily accomplished when broken down into lots of little tasks.
18Watt_sch1.png
mdog93 pfred22 years ago
Yes that does help, i need to reread it more thoroughly anyway referring to the circuit diagram to make sure i understand it. but i don't have time for projects like this at the moment but i hope to in the future. Thanks for your words of wisdom.
Man, I love analog and discrete design. IC's are great for making things work the first time, every time, but there is no better satisfaction than getting it right the first time with discrete parts. Wish you had a sound sample. I'd love to hear it.

Qa
pfred2 (author)  Quercus austrina2 years ago
I sort of do through an overdrive pedal I made.

http://www.instructables.com/id/GM-Arts-Overdrive-Pedal-Build/step13/Rock-On/

I should have linked to that article in the amplifier one. That pedal is unbelievable.
suckafish2 years ago
Excellent. Thanks for the schematic. I love Eagle. If I use the bill of materials on Eagle are all the values the right ones besides the Voltage Regulators?
pfred2 (author)  suckafish2 years ago
It should. Although I liberally substitute parts whenever I build circuits. Of special note is the input capacitor. Notice the row of pads on the board for it. That is so it can be changed out for different parts, that cap has a great effect on the tone of the amplifier.

Your best bet is to breadboard this, or any analog circuit before you commit to final parts choices. What is "right" with analog audio circuits is subjective. Although your final soldered board may and probably will sound different.

I think I used 12V regulators because that is what I had. It should even work with 15 volt ones. But 15V is the absolute maximum for the op-amp those regulators drive. This amp is pretty loud with 12V You may be a push the limit sort in which case use 15s

The op amp may be substituted as well for any dual with the same pin out.

All of this may be why I am more into analog circuit building today than digital. I have a problem with right and wrong. I've built a few of these amplifiers now, and no two are alike. The one I blew up is definitely wrong though!