I'm working on building a simple battery powered mini-amp to play my CBG's through. Inspired by the creations of nation member smojo, which he displayed at the recent UK fest in Birmingham, I'm experimenting with designs based on an LM386 integrated circuit. These tiny chips allow the construction of some amazingly compact yet great sounding amps (some of smojo's elegant little amps are shoehorned into very small tins).
I've found a lot of useful information at the websites of Beavis Audio (http://www.beavisaudio.com - see the "Smokey" and "Cricket amps") and runoffgrove (http://www.runoffgroove.com - info on "Little Gem" and "Ruby" amps). I've also investigated Maplin's LM386-based 1w mini amp and I downloaded the LM386 datasheet from National Semiconductor. However there are still a few things I'm struggling to figure out (either because they aren't well covered by the sources I've found or, more likely, because my electronics knowledge isn't sufficient). I wonder if any nation members have worked with these circuits and if so whether they can provide answers.
Firstly, some designs have a capacitor wired between pin 7 of the LM386 and ground (in fact the only design I can see where it's omitted is the Little Gem). The only description or explanation I can find is on the LM386 data sheet where pin 7 is described as "bypass". Any idea what they mean by "bypass" and what effect it might have on the sound of an amp if this is connected to ground via different capacitance values?
Also, I note some designs have a capacitor on the input (eg. Little Gem) while others don't (eg. Smokey and Maplin 1w). My first build doesn't have an input cap (partly because it was based on a Maplin PCB for convenience) and it seems OK. Can you suggest any reasons either in favour of or against adding an input cap?
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I was going to build my own also but not being too overly excited about soldering on a little circuit board, decided to give the 5w amp "harness" fro Guitarfuel. I like it so much that I ended up building two and have plans for a third.
I'm not sure what op amp chip it uses or configuration but produces upwards of 5w instead of the .5/1w for the LM386. I've found that it can support a little more substantial driver than the one that's provided. Within reason of course.
I used a Jensen P8R in the one build and a Quam oval from a console in the other. Both sound very nice, great tone and surprising volume.
Jim Woods > Mitchell MontgomeryJune 30, 2012 at 4:54pm
Yes, That was one of my first amps to build. I soldered in a 1k pot for gain adj instead of the jumper.
After a couple Lil Gem builds, I settled on the Noisy Cricket. If you get addicted and are going to build a few, buying the components from china, you can build 10 for about $100. If you just want one, buy a kit.
I did find out you only want to use mylar (gumdrop) capacitors for the non-electrolytic, not the ceramic ones..
I have been giving them away when giving a CBG. Everyone is amazed at the sound given a lttle 9v battery. Have fun!!
ive just made one with one of these, http://cgi.ebay.co.uk/MAKE-YOUR-OWN-CIGAR-BOX-TIN-CHOC-BOX-GUITAR-A..., you just connect your vol/tone to the output jack ,make a hole for the speaker in your guitar box,add a 9v battery and away you go.Its not the loudest but its certainly louder than an acoustic guitar
Just a thought. If you are really just looking for a practice amp... I use this one: http://www.voxamps.com/amplug/
I then plug in headphones or plug it into my home stereo's 'Line In.' I can play it through just about anything...
It sounds great and is really compact. But, if you are trying to build a small amp to fit into a similar Cigar Box, you may be better off buying a phono amplifier and wiring in some pots and a jack from Radio Shack...
Lmao... He was talking like he had actually built one until I showed him the data sheet... then the story changed.
Jkevn said:
http://www.national.com/ds/LM/LM386.pdf That diagram you posted looks like a variation of the lm386 amps, except the diagram is mis-labeled. 12v into pin 8 will let the smoke out, and it wont work without its smoke. 12v is the max voltage on a 386 chip (most variants), I dont see it putting out 8 watts, the N-4 variant only puts out 1000mw@16v.
These chips are less than a dollar each, you get a dollar's worth of fun playing it loud for a minute and watching it smoke....
has anyone tried this? a friend of mine found it on the yahoo cigar box forum, but the pinout of the lm386 doesn't match up with it. is it a waste of parts?
http://www.national.com/ds/LM/LM386.pdf
That diagram you posted looks like a variation of the lm386 amps, except the diagram is mis-labeled. 12v into pin 8 will let the smoke out, and it wont work without its smoke. 12v is the max voltage on a 386 chip (most variants), I dont see it putting out 8 watts, the N-4 variant only puts out 1000mw@16v.
These chips are less than a dollar each, you get a dollar's worth of fun playing it loud for a minute and watching it smoke....
has anyone tried this? a friend of mine found it on the yahoo cigar box forum, but the pinout of the lm386 doesn't match up with it. is it a waste of parts?
Replies
I was going to build my own also but not being too overly excited about soldering on a little circuit board, decided to give the 5w amp "harness" fro Guitarfuel. I like it so much that I ended up building two and have plans for a third.
I'm not sure what op amp chip it uses or configuration but produces upwards of 5w instead of the .5/1w for the LM386. I've found that it can support a little more substantial driver than the one that's provided. Within reason of course.
I used a Jensen P8R in the one build and a Quam oval from a console in the other. Both sound very nice, great tone and surprising volume.
[IMG]http://i97.photobucket.com/albums/l220/dou1/DIY%20guitar%20amp/DSC0...[/IMG]
[IMG]http://i97.photobucket.com/albums/l220/dou1/DSC00079.jpg[/IMG]
[IMG]http://i97.photobucket.com/albums/l220/dou1/DSC00107.jpg[/IMG]
Ron,
Those are some great looking amps.
http://www.ebay.com.au/itm/250530515447?ssPageName=STRK:MEWAX:IT&am...Would this be a good start? Mit6chell
Yes, That was one of my first amps to build. I soldered in a 1k pot for gain adj instead of the jumper.
After a couple Lil Gem builds, I settled on the Noisy Cricket. If you get addicted and are going to build a few, buying the components from china, you can build 10 for about $100. If you just want one, buy a kit.
I did find out you only want to use mylar (gumdrop) capacitors for the non-electrolytic, not the ceramic ones..
I have been giving them away when giving a CBG. Everyone is amazed at the sound given a lttle 9v battery. Have fun!!
This will also help when building http://www.instructables.com/id/The-Process-of-Building-a-Cigar-Box...
http://www.ebay.com.au/itm/250530515447?ssPageName=STRK:MEWAX:IT&am...
would this be a good start? Mitc6hell
http://www.voxamps.com/amplug/
I then plug in headphones or plug it into my home stereo's 'Line In.' I can play it through just about anything...
It sounds great and is really compact. But, if you are trying to build a small amp to fit into a similar Cigar Box, you may be better off buying a phono amplifier and wiring in some pots and a jack from Radio Shack...
Jkevn said:
That diagram you posted looks like a variation of the lm386 amps, except the diagram is mis-labeled. 12v into pin 8 will let the smoke out, and it wont work without its smoke. 12v is the max voltage on a 386 chip (most variants), I dont see it putting out 8 watts, the N-4 variant only puts out 1000mw@16v.
These chips are less than a dollar each, you get a dollar's worth of fun playing it loud for a minute and watching it smoke....
Michael Gajeski said:
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