# Amplify audio signal to high viltage

#### Seraj22

Joined Nov 7, 2013
6
Hello friends, this is my first topic in this forum, I have some experience in electronics and micro microcontroller programing.
Recently I was asked by a friend of mine to help build a circuit of an amplifier that has an aux input and amplify it to 220 volts with a power of 300 Watts,
the input is an audio signal with a frequency range of 0 to 1KH, the input is kind of sine wave. there are some ways to create the circuit using transistor but on the other hand they are not that efficient especially with that amount of wattage.

Is there anyway to achieve this using mosfets or tranformer? Maybe any other efficient way? A circuit will be highly appreciated.

I apologize if this isn't the right place for my topic, again I'm new to this forum.
Please also please excuse my english since I'm not a native speaker.

Thank you in advance for your help.

#### crutschow

Joined Mar 14, 2008
33,977
Is the lowest frequency really 0kHz (DC)?
The lowest frequency will significantly affect the design.

#### #12

Joined Nov 30, 2010
18,224
It is easily possible to make a DC coupled amplifier with a bandwidth of 1KHz, but almost any deviation in the shape of the alleged sine wave means it will have higher frequency components. How important is that to you?

We also need some better specifications like, do you want 220 volts RMS or some other definition of voltage like, "peak to peak"?
What are the characteristics of the input signal? What is its voltage? What is the impedance of the signal, or, how much current can the input signal deliver?

You apparently want 1.3636 amps RMS delivered to a load of 161.333 ohms, but is the load a resistor?
We can do the math, but there isn't quite enough to start with.

#### Seraj22

Joined Nov 7, 2013
6
Is the lowest frequency really 0kHz (DC)?
The lowest frequency will significantly affect the design.
crutschow
sorry for my mistake, start from 10Hz
Thanks!

It is easily possible to make a DC coupled amplifier with a bandwidth of 1KHz, but almost any deviation in the shape of the alleged sine wave means it will have higher frequency components. How important is that to you?

We also need some better specifications like, do you want 220 volts RMS or some other definition of voltage like, "peak to peak"?
What are the characteristics of the input signal? What is its voltage? What is the impedance of the signal, or, how much current can the input signal deliver?

You apparently want 1.3636 amps RMS delivered to a load of 161.333 ohms, but is the load a resistor?
We can do the math, but there isn't quite enough to start with.
if the cost is what you mean, then It is not a problem for me to use higher frequency components.

the 220v is RMS.

the load is not a resistor and will not draw constant current, So I was thinking about adding a controle circuit that maintane the voltage, or using some other feed back methode.

Thank you!

#### #12

Joined Nov 30, 2010
18,224
If the cost is what you mean, then It is not a problem for me to use higher frequency components.
My questions are not about co$t or price. Price vs quality is among the last calculations to do. One or two kilohertz is not, "High Frequency". It's more like, "child's play". My questions are about design parameters, and you have not answered most of my questions. Please examine your available input signal and tell us about that. Then tell us about the load and the quality of the power delivered to the load. How accurate? How fast? Without those numbers, we can describe the basic shape of the amplifier circuit, but we can not calculate the size of the parts. Beginners struggle with guessing the exact specifications. That's why telling us about the input (signal) and the output (load) are important. You tell us about both ends and we come up with, "What's in the middle?" Thread Starter #### Seraj22 Joined Nov 7, 2013 6 My questions are not about co$t or price. Price vs quality is among the last calculations to do. One or two kilohertz is not, "High Frequency". It's more like, "child's play". My questions are about design parameters, and you have not answered most of my questions. Please examine your available input signal and tell us about that. Then tell us about the load and the quality of the power delivered to the load. How accurate? How fast? Without those numbers, we can describe the basic shape of the amplifier circuit, but we can not calculate the size of the parts.

Beginners struggle with guessing the exact specifications. That's why telling us about the input (signal) and the output (load) are important. You tell us about both ends and we come up with, "What's in the middle?"
Sorry for misunderstanding
the frequency should be between 100Hz to 1KHz from an aux of a computer (Please take a look at the picture)

The accuracy +- 8% of the voltage, and the compensation time of 1 ms should be enough.

Thanks for the time and the effort

#### Attachments

• 114.8 KB Views: 7

#### crutschow

Joined Mar 14, 2008
33,977
the frequency should be between 100Hz to 1KHz
So is it 10Hz as you previously stated, or 100Hz?

What exactly is the load?

#### JWHassler

Joined Sep 25, 2013
306
Sorry for misunderstanding
the frequency should be between 100Hz to 1KHz from an aux of a computer (Please take a look at the picture)

The accuracy +- 8% of the voltage, and the compensation time of 1 ms should be enough.

Thanks for the time and the effort
That picture shows some very sharp transitions, or as they're also known, high frequencies.
How good does the reproduction have to be?

#### Seraj22

Joined Nov 7, 2013
6
So is it 10Hz as you previously stated, or 100Hz?

What exactly is the load?
that is right 100Hz, sorry I will edit my first post.

All what I was told that the load is a resistor with a variable value, for now please do not wary about the compensation I just need to amplify the audio to that range of voltage

#### Seraj22

Joined Nov 7, 2013
6
That picture shows some very sharp transitions, or as they're also known, high frequencies.
How good does the reproduction have to be?
I believe that this sharp transitions it the result of looping the wav file

the reproduction maybe realistically good so that the circuit will not be over complicated, all I actually need is an efficient amp that can produce 300 watt at that voltage, and yes I know that the voltage may go up and down depending on the input signal and the load on the output, for that to solve the problem I will have an MCU measuring the voltage (yes there will be voltage dividers and diodes) and affect the intput intensity by grounding it with PWM (there will be an inductor and a capacitor for a nice analog)

Thanks