Monday, May 7, 2012

Making a simple DIY mini guitar amplifier

I recently bought a little electric guitar for my daughter. It had a few issues (more on that in a future post), but all in all it’s a decent enough instrument. I wanted to build her a small portable amp to go with it, and this one, based on a TDA7052 audio power amplifier, came recommended: http://www.redcircuits.com/Page96.htm
It’s a very simple, compact circuit, and theoretically you can fit it into a cigarette packet. However, I was happy enough to fit it into a plastic box, which allowed me to use a slightly larger speaker and also not have to worry so much about cramming everything into a tiny space. I also left out J2 (the output jack), since I have no intention of connecting this to a larger amplifier. Here’s the box, speaker, speaker grill (actually, it’s a fan grill from a computer, since I couldn’t find a suitable speaker cover), jack and veroboard.
First we drill (well, bore) a large hole for the speaker in the lid.

Centring the hole:
Boring:
This is how it turned out, still requiring a little work with a file to smooth the edges.
A few more holes for the nuts and bolts, and here is the speaker in place:
Then in the box itself, we need an 11mm hole for the jack socket. For this I use one of my favourite tools – the stepping drill bit. I don’t know how I ever lived without one of these. They’re especially handy for drilling holes in stomp boxes.
OK, now that the speaker and jack socket are fitted, we need to think about the placement of the circuit itself. In this case I’m going to cut the circuit board to fit the box, since there are some very nice little slots to hold it in place already there.
I also cut a section out so that it doesn’t bang up against the speaker when the box is closed.
Test fit:
Now on to the circuit. Here’s the veroboard layout I drew up from the schematic itself (as with all images here, click for a larger version). Note that you have to cut the tracks between pins 1 and 8, pins 2 and 7, and pins 4 and 5 of the op amp, but you should NOT cut the track between pins 3 and 6 (I did originally, just out of habit, and then had to put a jumper wire in to correct the oversight). I've marked where the tracks should be cut with three "x"s.
Here’s a top view of the completed circuit:
And a bottom view (remember, unlike what you see here, you shouldn’t cut the track between pins 3 and 6):
All back in the box:
The battery, incidentally, was held in place with double-sided sticky sponge tape and wedged under the speaker. And here it is all closed up and ready to go:
It’s about as simple as you can get. No volume control (volume is controlled by the guitar volume itself) and no switch (the amp switches on automatically when the jack plug is inserted).

The sound quality is about what one might expect out of such a small speaker (tinny and easily distorted), but for a simple, highly-portable amplifier, it does its job. Battery life is pretty short too, so remember to unplug the guitar cable when not in use (you might want to consider wiring it up to accept a stomp box power supply, as shown here: http://diystrat.blogspot.com/2009/06/buhow-to-wire-up-stomp-box-effects.html). If you'd like to make something with a bit more oomph, while still being very portable, have a look at this post: http://diystrat.blogspot.com/2008/12/chiquita-amp.html.

16 comments:

Aralox said...

Really nice, I'm sure your daughter loves it!

Anonymous said...

PLz post a cmnt on the ic type .

sachindd said...

Nice i am making one lm386 IC for headphones to connect.

sachindd said...

How about making a DIY guitar tuner

George said...

Will it work with two 3W 4Ohm speakers wired in series?

stu said...

Hey George, that should work fine.

Unknown said...

Can i join it directly with a solid guitar pickup (without preamp)?

stu said...

Hi htin aung, yes you can.

guitar graph said...

I will surely try to assemble one of this DIY guitar amps It's a good use especially when i want to play inside my room in the middle of the night at a low volume.

clint said...

newbie here but what would the caps and res values be please or am I missing something??

clint said...

nope scratch that dumb comment I did miss it completely

Anonymous said...

What is the rod the goes from terminal 6 of the ic to the top of the board? Does it have a use?

stu said...

Hi, it's the 0v/ground wire for the chip.

Dynamata said...

How do I add a volume control?

Unknown said...

Please post a video of the amp in use.

petey twofinger said...

this is similar to a punch amp . the punch adds a jfet buffer and a volume control . there is two versions of the chip , tda7052 and then the tda7052a . the A version has an allotment to "just" attach a potentiohmeter ( volume control) in on two of the pins and you are good to go . this chip is rated at 2x the ouput power of the lm386 . the 386 is much much much more popular than this tda7052 amp . the 386 amp is a complete piece of trash , comparing it to a 7052 design , which is simpler less parts count , twice the power ,sounds WAY way better especially the jfet version\. so my point is this , if you are looking to build a small battery powered amp . this is it . one could also look on ebay or ali express and purchase mono class d amp boards and do it that way . adding a jfet buffer for the front end is always a good idea . i like oto build something like the runoffgroove tone mender eq and run that as well as a jfet buffer . the tda7052 amp or punch amp is the far superiors design to ANYTHING related to an lm386 . you cant polish a turd . the chip itself is not good . the lm386 is the worst component in existance period . anyone who argues does so out of ignorance as they clearly never used a 7052 because they are not as incredibly cheap as the lm386 . dont let anyone tell you differently . never build anything if it calls for an lm386 . the release will have undesireable artifacts . this is not my opinion , it is fact