DIY Stereo System
DIY Stereo System
Ever want a great stereo system but
know you are just better than buying one? If you are like me and have
more time than money, it may worth looking into. Because building a
stereo system isn’t as hard as it seems. Not that I’m so 1337 yet
that I can make one out of tubes, so solid-state will have to do.
(Only an audiophile can tell a difference in sound quality anyway)
First you have to find 3 loudspeakers,
two 8 ohms and preferably a 4 ohm one, but another 8 ohm will do.
The two 8-ohm speakers are for the left and right channels and the 4
ohm is for the optional subwoofer. To stay within my budget I went to
the dump and found 5 good loudspeakers. If you don’t have any luck
at the dump try ebay or a pawn shop.
I’m assuming you know how to put a
schematic together so build these. Remember to make two single
channel amplifiers if you want stereo.
I used the TL-071CP operational amplifier, but a
two-in-one or four-in-one package might be something to consider. I used two
fixed value resistors instead of a volume potentiometer, since I didn't have a stereo audio pot available. That way
both channels will always play just as loud. An audio pot with dual
potentiometers inside is ideal though. You will notice significant
distortion at high volume, so it’s a compromise between volume and
sound quality. But this circuit is the best one I could find when it
comes to heating, power usage and sound quality. I set the volume low
on the circuit and turn it up loud on my computer, that way I get no
This amplifier is just like the channel
amps, expect it autentates everything except bass. Us this
>SPREADSHEET< to determine the cut-off frequency. Or use this
1.4142 / (2*3.14*C1*R1)
The formula values are in Ohms and
Farads. The 220nF cap is C1 and R1 is 2* the 4.7 resistors. The 100nF
cap has to be half the size of C1 for the formula to be correct. If that's not clear just stick to the
circuit, the cutoff frequency is 137 Hz which is about right.
This is a type of voltage doubler which
will give you a split rail power supply from an AC source. The 78xx
and 79xx boxes are voltage regulators. The higher their voltage the
more volume you’ll get out of the amplifier. Make sure they are a
few volts under what your AC supply gives, and under the operating
voltage of the op-amps you choose. Between 12 and 20 volts is a safe
range. The xx part of the component name is the regulated output
Once you finish building those you
should have something like this.
Next up is the control panel which is
important for any DIY stereo system otherwise some fool might think
you bought it from a store. I didn’t have metal or metal-working
skills at the time, so I improvised. The picture is self-explanatory.
Next up wire everything together and
hope it works. If so, its time to start wrapping things up. Decide
which speaker should be the subwoofer, and open it up. The only way
to enter many loudspeakers is through the large bass speaker, which
can be unscrewed. Inside you will find fiber-glass insulation which
is not good for your health. Discard it carefully, or save it so you
can put it back in the speaker afterwards. It may or may not affect
the sound, depending on how audiophile you are.
This is what you will end up with. You
can see the built in cross-over filter inside, most speakers will
have these. Cut the tweeters connections, as they will only play
higher than bass frequency distortion from now on. Depending on your
skill you will have something that looks better or worse than my
Using professional connectors and
hook-ups for the AC, IN, OUT, and a nice locking switch and LED is a
must. The LED is not really as bright in RL as in the picture.
And there you go! This “guide” is
far from complete, but is should give you a good push in the right
direction. This system is not hi-fi, but good for a beginner in DIY