A Simple Hearing Aid


Commercially available hearing aids are quite costly. Here is an inexpensive hearing aid circuit that uses just four transistors and a few passive components.

http://streampowers.blogspot.com/2013/01/a-simple-hearing-aid.html

Hearing Aid Circuit Diagram


Parts:

R1 = 2.2K
R2 = 680K
R3 = 3.3k
R4 = 220K
R5 = 1.5K
R6 = 220R
R7 = 100K
R8 = 680K
C1 = 104pF
C2 = 104pF
C3 = 1uF/10V
C4 = 100uF/10V
C5 = 100uF/10V
Q1 = BC549
Q2 = BC548
Q3 = BC548
Q4 = BC558
J1 = Headphone jack
B1 = 2x1.5V Cells
SW1 = On/Off-Switch

Circuit Operation:

On moving power switch SW1 to ‘on’ position, the condenser microphone detects the sound signal, which is amplified by Q1 and Q2. Now the amplified signal passes through coupling capacitor C3 to the base of Q3.
The signal is further amplified by Q4 to drive a low impedance earphone. Capacitors C4 and C5 are the power supply decoupling capacitors. The circuit can be easily assembled on a small, general-purpose PCB or a Vero board.

It operates off a 3V DC supply. For this, you may use two small 1.5V cells. Keep switch S to ‘off’ state when the circuit is not in use. To increase the sensitivity of the condenser microphone, house it inside a small tube.

Comments

Post a Comment

Popular posts from this blog

Simple Active crossover Circuit Diagram with TL074

Image
This is a Simple Active crossover Circuit Diagram with TL074. An audio source, like a mixer, preamp, EQ, or a recorder, is fed to the input of the Electronic Crossover Circuit. This signal is either AC or coupling, depending on the setting of switch 51, the non-inverting input of buffer amplifier Ul-a, a section of a quad BIFET, low amp TL074 noise made by Texas Instruments op. This stage has a gain of 2, and its output is distributed to both a low pass filter made by R4, R5, C2, C3, and Uld op-amp, and a high-pass filter made by R6, R7, C4, C5, and op amp ULC.  These are12 dB / octave Butterworth filters. The response of the Butterworth filter was chosen because it gives the best compromise between the damping and phase. The values of capacitors and resistors varies depending on the selected connection that your device works. The filter outputs are fed to a balancing network made by R8, R9, RIO, R14 and potentiometer RLL balance. When the potentiometer is at its center position, t...
Keep reading

Build a Curve Tracer Circuit Diagram

Image
How to Build a Curve Tracer Circuit Diagram ? This is the simple Curve Tracer Circuit Diagram. This circuit Useful for checking diodes, transistors, triacs, SCRs, resistors, and LEDs, this curve tracer should prove useful in the experimenter`s lab.   Curve Tracer Circuit Diagram It displays the volt-ampere characteristic of a two-ter-minal device on an oscilloscope. This is a simple block diagram of the EZ-Curve. Current-limited AC signals are passed through both the device under test and a precision resistor to yield current and voltage readings.
Keep reading

Making an RIAA phono preamp

Image
Before we start today's blog post, I think I really need to clarify what we’re discussing. I’ve recently got back into vinyl in a big way. Part of the reason for this is the fantastic “Vinyl Decision” in Taipei, run by a couple of very fine gentlemen by the names of Mark and Terry ( https://www.facebook.com/VinylDecision / http://www.vinyldecision.com/ ). If you're in Taipei, and like music, pay them a visit. A recent purchase from there brought back memories of trying again, and again (and again) to play guitar like my guitar heroes as a teenager in the 1980s. In fact, vinyl is making quite a comeback worldwide. A lot of people are realizing that digital versions just lack some of the personality that vinyl can provide. Many of them are buying old record players/turntables and wiring them up to their modern amps. However, they are often disappointed to find that the output audio is very quiet and lacking bass. This is because records are/were recorded using a very specific f...
Keep reading