Punch Amp Build Pictorial

[nomorebetts]

I recently finished building a Punch 1W Guitar Amp and thought I would share my fun experience 


   


After picking up, (literally off the side of the road courtesy of hard rubbish collection), two rear bookshelf surround sound speakers I was looking for a low wattage, low cost, low parts count guitar amp circuit and stumbled across the Punch Amp by TCA:
http://www.diystompboxes.com/smfforum/index.php?topic=99271.0

Liking what I heard from the sound clips I immediately purchased the IC; TDA7052A, from http://www.diyguitarpedals.com.au/

Once the IC had arrived I quickly bread boarded the schematic on page 4 and was very, very impressed with the sound it produced.  I was actually quite surprised.  I was expecting the small 4 inch speaker to sound pathetic and toyish.  But it sounded clean, clear, crisp and got quite loud!

Encouraged by this I started to tweak it slightly to better suit the speaker and my guitar.
I lowered the volume pot to 250K as the speaker would start to distort using values above that and it was more than loud enough for its intended use as a living room/bed room/late night casual practice amp.
I also changed the 470nF cap to 330nF to roll off some bass and added a headphone jack.

My initial thoughts before I heard the amp was to couple it up with an 8 bit fuzz or other noise making circuit. But it sounded too good for this and decided to marry it up with an OD or distortion.

Breadboarding:
   

Wanting to stick with a low parts count and never having played with an Electra Distortion I decided to give it a go.  I added it to the bread board and it sounded good.  But I wanted more OD and less distortion so I tried different combinations of transistors and diodes and finally settled for a 2N2222 and 1N34As. This gave me a good spread from light OD to heavyish distortion.  All other values remained stock after lots of fiddling... go figure.

[nomorebetts]

Happy with what was on the bread board I fired up DipTrace and created the schematic:



I usually create a PCB layout and etch my own boards but this time I thought I would do it on Perf and used DIY Layout Creator to create this:



It was also around this time that I figured there was plenty of room in the speaker for more circuits so I decided to re-employ a Rebote 2 Delay which is destined for retirement once I finally get around to building the Echobase or Multiplex boards that I have gathering dust.

Populating the board:
 

Finished board, after re-thinking the onboard pot and minus the delay board.

[nomorebetts]

With the board populated it was time to measure up and drill the speaker box.
I also made a lame attempt at shielding using aluminum kitchen foil and added a drawer handle 

Picturing the parts layout:                        All measured up:
   

Inside the speaker:                                   Drilling:
   

For some hardware the thickness of the wood required me to bore out a larger hole halfway down the hole for the nut to fit in.  Using these types of drill bits I was able to do this relatively easily:
http://upload.wikimedia.org/wikipedia/commons/a/a9/Spade_bits.JPG

[nomorebetts]

I had originally hoped to be able to somehow remove the entire front wall of the box but it would have either required melting the glue or sawing it off with a hand saw.  Not wanting to do this I convinced myself I that I would be able to get everything in and mounted through the little opening for the speaker... this proved to be optimistic at best as my hand just barely fit and it turned into key hole surgury using long nose pliers and a flat head screw driver.

I did however have the good sense to hot glue all the socketed components into place so they couldn't be knocked out while being roughly pushed around and mounted.

Maintenance on this thing will be a nightmare!  

I really hope that nothing vibrates loose over time which will probably happen due to it all being INSIDE the speaker cabinet  


Everything ready to be mounted:             Two hours and many curse words later:
       

The box being wooden and roomy I was able to use up a metal dc jack and 24mm pots from an earlier botched order.


Awaiting knobs:                                        Knobs on, time to rock!
   

And there you have it!  -  My Punch 1W Guitar Amp

I'll try and record some sound samples soon.

Thanks for looking and I hope you build one too.

Cheers!

[therealfindo]

Great work!!

I'm also in the middle of repurposing some 4" bookshelf speakers into a Punch - I've got the amp box / chassis done, and just need to build the cab.

I have a question re the headphone - I'm using an open, switching jack so that I can plug my 10" cab in and it will bypass the 4" speakers inside, but when I plug headphones in, I only get one side. I am using a stereo jack, and I tried connecting the tip and ring both to the output, but that then kills it when I plug the mono 10" cab plug in... any thoughts?

[nomorebetts]

I also wanted to do what you're describing and ran into the same issue!

Unfortunately it seems a switch to choose between mono or stereo output is required.
Or two output jacks -mono and stereo.  I decided to just have the single stereo output in the end.

Check out this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=104750.0

[chptunes]

Good idea.. I like it.

I put a Punch in an abandoned 1x8 solid state combo cabinet.. Plug-n-play style, with the Volume (trim pot) preset to 'conversation level' (about 80k Ohms).

[zedsnotdead]

Congrats!!! Very nice build!!

I am about to star a punch amp myself, but then I saw this post and it is a awesome ideia!

So I have a couple of questions if you dont mind answering.
1- in your vero layout, there are 2 dpdt+1spst, but on your schematic there is only 1 dpdt+1stsp. Am i missing something?
2- also in the schematic thare are 3 trannies, but 4 on vero?

thanks a lot!!

[nomorebetts]

Cheers!
The extra DPDT and tranny plus associated parts are for the second millennium bypass circuit which I didn't draw in the schematic.

If I was to do it again I would use 3PDTs and the regular bypass wiring instead to simplify things.

Good luck with your build! I look forward to seeing what you come up with.