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Minty Guitar Amp

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dudemcfly

New Member
Hello this is my first thread and my first electronics project. To be honest I really dont know anything about components or anything, just a basic understanding of electricity and how to solder. I saw many project ideas for using a Altoids mint box. I thought having a mini guitar amp would be very cool so I downloaded the instructions from mintyamps.com. However I am having trouble putting the components together. I already have everything on the list of parts except the potentiometers and one of the two jacks.

Here is a link to the instructions.
http://www.electro-tech-online.com/custompdfs/2010/12/Minty20Amp20assembly20instructions.pdf

The diagram in the PDF does not show how some components connect to the others. Specifically, the .047 capacitor/input and the 100 capacitor/LED/output. Is it me or are these parts not connected to anything else? Assuming they are supposed to be connected to something else, can someone tell me exactly where? I also dont understand how and when to use normally open and normally closed jacks. Could someone explain that to me? What I'm going for is the basic layout in the PDF but I will have an on/off switch, and I need to understand N.O. and N.C. jacks so that I can make the speaker turn off when I plug something in to the output.

I am aware of the Little Gem and Ruby amps from Run Off Groove but I already have what I need for this amp and have my mind set on it.

Also, here is a picture that shows the board a little better.
http://blog.makezine.com/mintyAmps.jpg

If someone could explain all of this to me it would really help. Sorry about the big explanation but I'm not really sure how to describe all this. Thanks, I really appreciate it.
 

audioguru

Well-Known Member
Most Helpful Member
There is no schematic so you don't know what connects to what unless you buy their kit with their printed circuit board.
It seems to be missing very important parts that are shown on every schematic on the datasheet for the LM386 amp IC.

The circuit board shows the 0.047uF input capacitor and the 100uF output capacitor.
 

dudemcfly

New Member
OK, well I went with the Little Gem amp diagram. Thanks for the tip audioguru. It would still be helpful if someone could explain normally open and normally closed jacks. Thanks.
 

Jon Wilder

Active Member
Switching jacks have an extra contact on them that the tip and sleeve make contact with either when there's a plug installed or no plug installed.

A normally closed jack will have its tip (and perhaps the ring if present as well as the sleeve) making contact with the on jack switch contact when there's no plug installed.

A normally open jack will have its tip (and perhaps the ring if present as well as the sleeve) making contact with the on jack switch contact when there is a plug installed.

Normally closed jacks are used on guitar amplifier inputs. No other reason to use a normally open jack on a guitar device unless there's some special signal path switching going on in the circuit. On a guitar amp with a normally closed jack, you connect the switch contact to the sleeve of the jack. This grounds the tip connection of the jack when you're not connected so that the input doesn't "float" and create a bunch of hum noise.
 
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