Audio Amplifier diagrams

[D31196]

hello guys iam new iam 15 and i will build a simple audio amplifier for my pc speakers
so what do you suggest to me? any good diagram for an amplifier 100-200 watts?
i have all the toold sordering iron , tin ....... thanks

 

[magnatro]

200 watts?! good!
https://schematics.circuitdiagram.net/thumbs/jdv1266243356m.jpg
this might be good!
200 Watt High Quality Audio Amplifier « Circuit Diagram

 

[D31196]

thanks i will check out now

 

[D31196]

lol if you see my threads that diagram is already

 

[Nigel Goodwin]

It's still a crap and useless circuit

But you don't need 100W for PC speakers - you would blow the speakers to bits.

PC speakers that claim 200W or whatever are usually only 5 or 10 watts.

 

[magnatro]

for a beginner circuit.. check out this.
**broken link removed**

 

[D31196]

lol no my pc speakers are a car subwoofer

 

[cr0sh]

lol no my pc speakers are a car subwoofer

Then why don't you get a car audio amplifier? That's what I did when I was your age...

Doing so, you will likely end up with a better system than what you could build, and probably cheaper too - unless your goal is to learn audio amplifier design (which is a good reason to try!)...

 

[Jon Wilder]

Before I say what I'm about to say I will first start by saying that an understanding of "average" and "peak" power MUST be obtained.

"Average" power is the rating that most manufacturers incorrectly referred to as "RMS Power". This is because the RMS value of voltage and current are used to find the average power that the load will dissipate.

So basically when you see a rating of X Watts RMS, that's actually X Watts Average. The Peak Power is always DOUBLE this value.

That being said, if you want 200 Watts Average out, you have to design the amplifier to put out 400 Watts Peak (meaning 400 watts at the peaks of the sign wave...not that it will put out 400 watts maximum average).

When designing ANY amplifier, the first thing to consider is the load and the power supply. After all, the power has to come from somewhere right?

Now we need to figure out how much voltage the load will require across it to achieve the required output power. This is done very easily by working the P=(V^2) / Load Impedance equation backwards -

P x Load Impedance = V^2

Find the square root of V^2 to give you the voltage.

So...to figure out how much DC voltage we'll need, we need to know what the required voltage would be to deliver the required PEAK power that will give us 200 watts average power.

Assuming an 8 ohm load -

400 Watts x 8 Ohms = 3200

Find the square root of 3200 -

56.57 Volts Peak required at the load

The DC voltage of your supply MUST be equal to or greater than this voltage under load. Now let's check our math. Let's find the RMS value of our required peak voltage -

RMS Voltage = Peak Voltage x 0.707

RMS Voltage = 39.98 Volts

RMS is 70.7% of the peak voltage, which explains where the 0.707 constant comes from.

Now let's see how much average power 39.98Vrms will give us across the load -

(39.98V^2) / 8 Ohms = 199.98 Watts average...close enough to our spec'd 200 Watts average power

Now to find the required peak current, we simply take our peak voltage and divide it by the load impedance -

56.56V / 8 Ohms = 7.07 Amps peak current

So we need a dual polarity supply capable of supplying at least 57 Volts @ roughly 7 amps on each supply. However, each supply doesn't need to be rated to source 7 amps at the same time because the two sides of the amplifier are never drawing current from their respective supplies at the same time due to them operating 180* out of phase with each other. A transformer capable of delivering at least 3.5 amps @ 90 volts across the full winding would more than suffice since the output devices will be drawing from the + and - supplies at opposite times for the +/- swing of the output signal.

What you say? Where do you get 3.5 amps from 7 amps? This is because with a bridge rectifier and the center tap grounded, the bridge rectifier's + and - outputs become your dual polarity supply. They're operating just like a full wave grounded center tap rectifier circuit would, but at opposite polarities from one another. On a full wave grounded center tap rectifier you get DOUBLE the full winding current but at 1/2 the full winding voltage. This is due to each 1/2 of the winding having a 50% duty cycle and you're only having to pull current through 1/2 the winding at any given time rather than the full winding running at a 100% duty cycle and having to pull current through the entire winding. Because only the + OR the - is ever having to source the current at any given time due to each side of the amp operating out of phase with one another, you only need one OR the other to supply the full 7 amps at any given time.

I'm thinking a 90V center tapped @ 3.5A full winding current should suffice for this. Along with a bridge rectifier and the center tap grounded this should give you two supplies of opposite polarity that are roughly 60-63V @ 7 amps each when not drawn from at the same time. This amounts to a VA of 315 Average, and 630VA Peak, which should more than suffice for the output power we're seeking.

Once we have the supply out of the way, we need to select output devices that can handle this voltage and current as well as make sure the power dissipation rating exceeds the amount of power each device will dissipate when the output signal transitions from positive to negative and vice versa. It's a popular misconception that output devices are at full dissipation at the peaks of the wave when actually they hardly dissipate anything at the peaks (if they were the load wouldn't see any power at all). In reality though they dissipate power during the transition period when the signal is transitioning from positive to negative and vice versa, with the highest dissipation occurring 1/2 way up the swing on a push-pull amplifier while hardly dissipating anything at the peaks (because the load is dissipating it all at that point). The instantaneous dissipation can equal up to DOUBLE the rated dissipation since for 1/2 the swing they're dissipating nothing, which makes the average dissipation equal to or just below the dissipation rating.

If you find output devices that can handle the voltage but not the current, you can parallel several of them together and use low value resistors on the emitters (or sources if using MOSFETs). This helps to "load balance" (i.e. ensures that each output device is seeing the same current).

Think of the power supply in an amplifier as your fuel/air mixture on a motor while the output devices are your rotating assembly in a motor. If the source of required power isn't there in the first place (i.e. not a big enough fuel/air charge) you're not gonna get it. At the same time, if the power source is there but the rotating assembly cannot handle the power (i.e. the output devices), you're gonna blow things up.

 

[D31196]

thanks and is true i can buy a car amp but i love to build one so its like my goal and u helped me very much

 

[maxx]

If you want just for subwoofer you can try this 35 watt based on TDA2030 or if you want to build a multichannel amplifier you can try this based on LA47536 or something else based on TDA or TA ICs .