Guitar to AV Receiver Interface

Have you ever wanted to amplify your electric guitar by plugging into an AV Receiver (home stereo)? Ever tried rigging up a 1/4" mono instrument plug to RCA patch cable? If so you most likely were disappointed when it didn't work. Most modern consumer grade AV equipment only has output power amplification which has to be fed with Line-Level Pre-Amplified signals. Musical instruments with passive pick-ups have a high impedance low signal level output that has to to be gradually stepped up with pre-amplification.

Article Features:
Simple two transistor stage pre-amplifier circuit, with a high impedance input stage suitable for musical instruments with passive pick-ups and an output stage with enough signal level to feed AV equipment. A brief description of the processes I used to fabricate the clear acrylic case I made. The input stage of this amplifier circuit is a Common Collector amplifier which has high input impedance, low output impedance, and high current gain. The output stage is a Common Emitter amplifier which has medium input and output impedance, and high power gain. The input and output is decoupled from the 3V DC supply power by C1, C2 & C3, R1 & R3 control the base current of Q1 & Q2, and R2 & R4 control the output current of each transistor stage respectively.

I used point-to-point construction for this circuit, however it could be built on a PC board if desired. I used aluminum duct tape to form power rails on the inside of the acrylic case. Since the tape can't be soldered I used small pieces of tape to fasten the connection points to the components. It was challenging to make reliable connections with this method. Alternatively copper tape, or wire could be used.

Parts List:

I used male RCA plugs as the output termination because I wanted a compact inline connection, alternatively female RCA jacks could be used with patch cables. I connected the RCA output plugs in parallel to feed both the left and right channels of the AV receiver.

Standard AV RCA phono plug on center spacing is 13mm with a 10mm panel mount hole.

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Make Your Own Cigar Box Guitar / Mp3 Player Amplifier

I've wanted to create a Cigar Box Guitar and Amp for quite some time, and it seems like the Instructable Sound Hack and Battery Powered contestst were just the extra incentive I needed to give it a try.

This Instructable shows how to create a Cigar Box Amplifier, of course it can also be used as an MP3 player or Phone amplifier. I decided to build the amplifier before the guitar since it's certainly easier, but hopefully a Cigar Box Guitar Instructable will follow soon!

If you haven't heard of Cigar Box Guitars, you should check them out. YouTube has lots of videos demonstrating amazing sound from these 3 stringed instruments. 

Here's an example of a CBG in Action:
http://www.youtube.com/watch?v=iIIEhH7xOXg

Actually they don't all have 3 strings, but hey this is about the amplifier anyway,
let's build one!What's Needed for this Guitar Box Amplifier Instructable?
Cigar Box - I have a friend who occasionally smokes a cigar, he tells me they are all legal (at least somewhere in the world ;-) ). I noticed these can also be found at Yard Sales, on eBay and sometimes for free in Tobacco Stores. LM386 chip based amplifier circuit - I got a kit for this from http://tymkrs.com/, (some sites sell pre-soldered kits as well) but you can likely make your own. Parts needed are: Potentiometer, LM386 Chip, Resistor, 2 Capacitors, 9V battery connector and Guitar jack. 8 Ohm Speaker (I got mine from an old projection TV) Switch (optional) - didn't come with the kit, but I thought it would be handy to save on batteries. Wire Miscellaneous parts for decoration, most important is something to cover the speaker, (I used the plastic which originally covered the speaker on the TV). Optional: Handle, Legs, battery holder, Something to cover keep the box closed,  Tools Needed for This Instructable: Drill  Soldering Iron and Solder (unless you buy a pre-soldered kit) Hole Saw (optional) to cut the speaker hole (or use a drill and Dremmel or X-Acto knife) Now that you have your parts... 
Step One is to solder together the kit, as seen in the picture below. 
(It's a good idea to get a general feel for where all the parts are going to be installed before you actually start cutting wire and soldering. You'll notice I left way too much slack on my speaker wire)

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