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Digest of headphone amplifier construction articles.
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From: johnr@tvnews.tv.tek.com (John Reynolds)
Subject: Incredibly Cheap Headphone Amp
Organization: Tektronix TV Measurement Systems, Beaverton, OR
Date: Tue, 30 Mar 1993 22:28:09 GMT
A previous poster mentioned an LM386 based headphone amplifier. Here's
a circuit for one I built last night. I think this is probably the most
minimal implementation for such a beast.
LM386 o +9 volts
|\ |
3 | \| 6
In ----|+ \ 5 + 330uf
(From guitar) 2 | >-------||----o Output (to headphones)
-|- /
| | /|4
| |/ |
| |
-------------*-----*--------------Gnd
The LM386 is run in its "minimum parts" configuration. See the National
Semiconductor data book for more details. The LM386 is available at
Radio Shack for $1.09 and the cap is also a RS part for $0.99. Use the
volume and tone controls on your guitar / bass. There seems to be plenty
of clean power to drive a set of headphones.
Obviously, other enhancements are possible. I also experimented with
summing the output from a tape deck in with my guitar and that seemed to
work ok too. Adds to the complexity/cost, though.
The "bang for the buck" quotient of this circuit is so good, you really
owe it to yourself to build it up and check it out.
BTW, I think the poster who mentioned that his headphones were "heating up"
with an LM386 amplifier may have omitted the 330uf cap from the circuit.
John Reynolds
Tektronix TV Division
Beaverton, OR.
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From: jjkullma@vela.acs.oakland.edu (J. J. Kullmann)
Subject: CIGAR BOX AMPLIFIER
Date: 21 May 1994 05:01:28 GMT
CIGAR BOX AMPLIFIER
After months of looking around the local guitar shops looking for something
cheap that I could plug my guitar into and listen through walkman style
headphones and finding nothing, I decided to attempt building my own.
After a little effort and experimenting I finally built a low noise amp
that works wonderfully. This amplifier is driven by one 9 volt battery.
The op amp is a LM386. The gain with this configuration is 200.
I have checked this diagram carefully. It is correct.
Components (minus the headphones) only cost me $15.00 at my local Radio Shack.
You do not have to an electronics expert to build this. I have no real
electronics experience and was able to hack this together. Must be heard to
be believed.
You could build this on a little perfboard and actually fit this into your
guitars body cavity.
IT WORKS FOR ACTIVE AND PASSIVE PICKUP ARRANGEMENTS
+9Vdc
|
|\ | 10uF
3 | \| | |
Signal in-------|+ 6\| |
| 1\| +|| 220uF
| 8\_____________||___________
| / | || |
2 | / | || |
----------|- / ------ |
| | /|4 ------0.1uF Low Impedence Speaker
| |/ | |_______/\/\/\____ |(8 ohm Walkman Style)
| | 10 ohm | |
| | | |
|_____________|___________________________|___|
|
GND
Materials
1/4 " Jack for guitar signal input
Head phone jack (stereo connect left and right channel)
1 9 volt battery terminal connector and 9 volt battery
Capacitors one each: 10uF, 220uF, 0.1uF
1 10 ohm resistor
1 LM386 op amp
8 pin IC base (optional, I used one because I did not want to burn up the IC)
SPST switch (optional, I used one so that the battery would last longer)
Perfboard of choice.
You can go gonzo with different boxes (I used a cigar box for the first
one that I built) or you can fit it into the cavity in your guitar
(I used velcro to keep the battery from flopping around) or you can add
LED bar graphs (I don't know the number for the control chip) etc.
I am new to the net and do not know how to cross post. Everyone can feel free
to share this anyway they want.
Comments and suggestions are welcome.
Thank you and enjoy!!!
James Kullmann