P = U^2 / R
This is the main formular as you shurely know. It uses the AC - output voltage at the speaker.

I just convertet it so you can use the DC voltage supply at the condenser now, but at first you have to subtract the drop voltage of amp because it´s level is not 100%.


(I´m sorry, because it´s still difficult for me to write in english, however I´ll try to explain tomorrow a bit more details)

 

Here's the formula to calculate the maximum peak power at the speaker:


It takes into account the voltage drop across the driver transistors.

__________________
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http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

"Maximum Peak power" is confusing because it is simply double the RMS power number.

When the volume control of an amplifier is turned up way too high then it -produces "maximum peak power" because the output is extremely distorted square-waves and the usually unwanted harmonics are the same power as the RMS power of the amplifier.

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Uncle $crooge

 

Ok if we could get back to making an amp. I looked up the specs of a LM1875 since that was suggested earlier. There are two schematics in the specs page. First off which one would be better. Second off I have some questions about the diagram.

I am familiar with to wire up something using a diagram but I am confused about the five different inputs that are used. This chip has the following pins.

+ IN
- IN
- Vee
Output
Vcc

Could I get a simple explanation of what is what. Such as power supply and the audio source.

I know this can use a 16-60 V power supply but I'm unsure of the amp rating that should be used for the power supply.

If I can figure this stuff out I should be much closer to building an amp

 

The datasheet shows a schematic of the amplifier with a dual supply and another amplifier with a single supply. A pcb layout is shown and it has wiring for either type of amplifier.

The input to the amplifier is Vin and ground.
+VCC is the positive supply.
-VEE is the negative supply if you are ussing it.
Ground is the common of the supply.
Output and ground connect to a speaker.

If you use a 50VDC supply then the max low distortion output power is 25W. Then the input signal level is 673mV which is pretty high. You probably need a preamp to amplify the 150mV from a line-level source.

When the output is 25W then the LM1875 heats with 15W. So the total power from the power supply is 40W. You won't play music or speech at full output all the time so a transformer with a power rating of 30W will be fine. For stereo the transformer should be 60W.

To make 50VDC the transformer needs to be 36.5VAC. For 60W then the current from the transformer will be 1.64A.

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Uncle $crooge

 

look at this amp
it works pretty good, its cheap and its ready to go
http://www.apexjr.com/amps.html

 

I looked through there and I don't amps that powerful and I personally don't think they are cheap.

I have two 50W speaker rated at 6Ω (man I love that menu of common symbols) and wish to have a stereo amp on the cheap.

A friend of mine yells at me when I tell her how I'm trying to do something when asking for help and tells me to say what I want the end product to be.

I want to plug in a stereo audio source and have it amplify it for the speakers I listed above. All I want to do when this is done is plug in something hook the speakers up and plug it into power, and have one volume adjustment on it. I would also like to use a premade power supply, i don't feel like building one of those too.

I might scratch this project if i don't start understanding it soon

 

There are still a few electronic kits manufacturers in the world. Make an amplifier kit that has everything that is needed.

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Uncle $crooge