Look at the amplifier I built :)

[Solid Snake]

My Amplifier

Tell me what you guys think. I designed and built it by hand. It's good for about 120 watts. I'm designing a much more powerful version and building it soon hopefully. It's definately one of the most rewarding things I've done recently

[Xeroid]

Wow, that brought back memories. I once took an electronics projects class when I was in college. We had to design our own circuit, etch the circuit board, solder the components to the board, and mount it in a case. I did a signal generator.

Glad you are enjoying yourself.

[Brainchild]

That is great, I wish I could do something like that,but I'll just have to stick to testin them

Very cool, Snake. Now make me a 1,200 watt bass guitar amplifier.

Now I'm looking forward to electronics class.

[TOAD6147]

Very interesting. I've not done any of this stuff in quite a few years. Where do you find such a massive heatsink and will this be the size you use in the final revision?

[Solid Snake]

The heatsink is not that massive... Well compared to CPU sinks it is. I think it came off dead stereo equipment. It's about 5" square. You can never have too many heatsinks, not exactly an off-the-shelf part so I collect them when I can. The heatsink I'm using in the next project is about 5" tall, 2" deep and a foot long, probably have it cooled by a few fans too. For every watt that goes to the speaker, about one goes to the heatsink too so it has to be able to get rid of heat quick. I want to etch a board for the final design, I'm sick of twitchy jumper wires, it gets too messy after a while. I've never etched a board before.

[RedFury]

It's not really all that hard, you just have to have the right stuff. You chemically etch the board by removing the copper you don't need for the circuit by covering the circuit area with something you can remove later that won't be affected by the chemical etch. We silk screened something on ours, or used some kind of stencil.

[Zac]

Hi there, I’m a passerby. I was looking up something about amplifier when I came upon your design, pretty unique. It’s not bad for a first go (probably better than my first go) I my self design amps.

To be totally honest I’m surprised if it works, I have never came across the topology, the class AB output was a good idea(good efficiency), However improvement can be made on the rest of the amplifier. When I say it’s not bad for a first go I meant that you understand the approach and how transistor work. Now; the reason why this amp will work is mostly due to the variable bias resistance, so let improve. Let’s star with the input stage R1, R2, C1, C2, Q1, Q2 not needed. Only one input transistor is needed thus only C1 and R1 is needed, R1 will help to match impedance and c1 will couple the source to the input within the bandwidth (frequency response)of the amp,47uf is good may try 22uf 10uf 4.7uf is my choose of input coupling sometimes 1uf because of the input impedance this will give the 20hz and a bet under frequency response, but will decrease max power kinda mostly because any thing under 20hz humans can’t hear so why amplify it, will with Big power amp you will feel it . Now you have two chouses for Q1 common emitter or common collector, the different between the two is that the common emitter have both voltage gain and current gain, the common collector mainly have current gain the voltage gain is lest than one or lest than unity. Now I’m going to tell you some thing that I’m yet to read in any amplifier book , now the transistor have limits one of the limits is the base emitter voltage which with most transistor is under 5volt. So having said that, the voltage gain of the stages before the output transistor should not be more than 5 volt peak to peak when using direct coupling, however will be ok if you are using capacitor coupling because you can bias the next stage within the 5volt limit.

The second stage type will be determine by the type of first stage used, now if the first stage was a common emitter then the second stage will be a common collector, and if the first stage was a common collector then the second stage would be a common emitter. Most transistors have fairly big gains, so with just those to stage you will have the volts and current you need to push the output transistor to the required limits.

Note well the first and second will need to be A Class this is ok because they are low power stages compared to the output stage and this isn’t going to affect the efficiency much, and it will increase the quality of the sound. How to do this? Simply bias the transistor so that it sits at half the peak to peak voltage needed. For direct coupling ½ 5volts any thing over amp will clip and for capacitor couple ½ Vcc(half of the battery voltage).

Driving the output stage. The final stage (output stage) bias voltage will determine amplifier Class, Half Vcc A Class, any the more or less AB Class, almost off B Class.( completely on you have a B Class Heater! This will more keep you warm than given good sound)

This is looking lengthy so if any one wants to know more contact me or replay I check back as soon as possible.