| Part's
List:
|
R1 -
100K
R2 - 330
R3 - 100
R4 - 22 (2 - 4.5V)
R4 - 100 (5 - 12V) |
|
C1
- 4.7uF
C2 - 4.7uF
C3 - 100 - 1000uF
C4 - 220uF |
|
P1 -
100K
D1, D2 - 1N4148
Q1, Q2 - BC549
Q3 - BC559 |
|
|
|
| Technical
Specifications:
|
Supply
Voltage: 2 -
12V
Energy Consumption: 10mA/3V - 30mA/12V
(measurements
taken using a stereo version)
Output Power: 300mW |
|
|
|
About
this Circuit
| |
This
is an improved version of headphone amplifier
I've built many years ago. I wanted so much to
share it with you because this simple circuit
has done a great service to me through all these
years. It is very simple and reliable, hard to
break, offers a lot of power, excellent sound
quality, it is built with just a few simple parts
and more importantly it has a very little power
consumption. With just two AA batteries it can
work for a very loong loooong time ;).
|
New
Features
| |
Since
I built this amplifier a long time ago I decided
to make an improved version now. The schematic
has to protections added that aim at the similar
purpose. First protection that consists of R4
and C3, simply reduces the noise while turning
the amp ON and OFF. Instead of applying the
full supply voltage to the amp, resistor R4
slowly charges the capacitor C3 and produces
the soft turn ON and soft turn OFF effect. Second
protection is resistor R3 and this one reduces
the noise while connecting and disconnecting
the headphones form the headphone jack. The
resistor doesn't lower the volume of the amp
but simply simulates the headphone resistance
when headphones are not connected to the amp. |
| |
When
designing the PC Board for this circuit I overestimated
the size of the board a little bit and the board
was simply to large (4cm x 5cm). In result I
decided to cut the unneeded board thus making
the project smaller. After looking at it for
a while and measuring the size again I thought
about the familiar name. Since the size of the
project is 4cm by 4cm it would be nice to give
it a name 4x4 since the amp is pretty powerful
as for its small size.
|
What
can it be used for?
| |
This
handy amplifier can find endless uses around
the house. For example it can be used as a
general purpose stereo amplifier for devices
like walkmans, radios, CD Players, computers,
DVDs, VCRs, TVs, etc. Or in electronic field
as a great audio amplifier for radios, microphones,
or used as a audio tester.
As
for myself I decided to build three stereo
versions, one for my computer for my newly
added front panel headphone jack, another
one in an external enclosure for my TV/DVD/VCR
that lets me watch the movies at night while
not interrupting anybody in the house, and
the last one I am using as an audio tester
for my electronic projects.
|
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