Acoustic Guitar Preamp

I like Guitar very much and taking classes and I got new yamaha FSX315C Electric Acoustic Guitar, it comes with electronics and audio output of 1Kohm impedeance, So I thought I could make one small preamp with OPA2134 JFET opamp

acoustic guitar preamp

acoustic guitar preamp pic2

I soldered 3.5mm female stereo sockets on both sides of amp as INPUT and OUTPUT so I had to use 1/4inch female to 3.5mm male connector. I have connected the preamp circuit to my PC and recorded few tracks I have played using audacity software.
audio track1:
   I hope you like it.
I will add few things to the circuit like Equalizer thing and post the schematic. Thank You

Class A MOSFET amplifier

I always enjoy building audio amp’s particularly Class A topology.

PCB’s of class A MOSFET amp


pic c a .png

pic c a 2.png

pic c a 1.png

PCB’s of class A MOSFET amp.

PCB class A .jpg

assembled class A amp board.jpg


irfp250n mosfet.JPG


power amp ca .JPG


I used two MOSFET’s  (IRFP250N) one is configured as current source and the other one is to amplify the signal, for the input stage I have used JFET 2SK209 provides high input impedance and the

output impedance of the amplifier is 2.6ohm’s

output of the amp is 5watts at 3% THD and each MOSFET dissipates 9.6watts of power efficiency of the amp is 26.04%


LED candle avr

This is a simple project, called  LED candle. I will be using yellow LED’s of 2 and a simple PWM code that runs on AVR (ATmega328p) chip make’s the LED flickering that almost looks like candle.  😛  for candle I will be using  LED’s+translucent paper.

two-yellow-leds       translucent-paper


LED candle





code is very straight , Simple PWM code runs on ATmega48/328p

#define F_CPU 1000000UL
#include avr/io.h
#include util/delay.h

#include avr/interrupt.h

void timer1_init(void);

void timer1_init()
DDRB |= 1<<PINB1; //
DDRB |= 1<<PINB2;

TCCR1A |= 1<<COM1A1 | 1<<WGM11; //
TCCR1A |= 1<<COM1B1;
TCCR1B |= 1<<WGM12 | 1<<WGM13 | 1<<CS10; //
ICR1 = 49; //top value

int main(void)

OCR1B = rand() % 47 + 1;

OCR1A = rand() % 47 + 1;




pictures of my old projects.

Old projects.


mini tank robot

Mini tank robot was my one of oldest project. I built it for fun, no use only for fun.  I did used ADXL335 accelerometer for inclination detection , AVR microncontroller (ATmega164P) for processing and controlling  and L293D motor driver Chip and BO series motor.


robot 2
POV display based on ATmega48


lm4752s amp pic1    lm4752s amp pic2






volume indicator

Volume indicator Indicates the level of audio signal.(this project is under construction.. will update soon )

INPUT devices: microphone                                                                                                         OUTPUT: LED bar graph                                                                                                               processing: AVR (ATmega32A)

My construction:

volume unit meter version1


microphone pickup’s the audio signal and BC546 preamp amplifies the signal to the level 1.8Vpp max, so that ADC can read.  BC546 collector feedback bias circuit.



audio fed to the ADC pin of ATmega32A

aaded voltage regulator (2sc1383 + 5V6 zener), we can also use LM7805 regulator.

volume indicatorpic1.jpg






AM transmitter

I am always interested in building radio circuits. am transmitter, for construction, I used copper clad boards and really like the construction, not neat though, I do remember that I sprayed thicke…

Source: AM transmitter

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