sounds like a great solution (pun intended)

Submitted by rich gallagher on Mon, 08/06/2012 - 13:56

john, i'm so excited about finding this amp! i make cigar box guitars and amps and sell them all over the world - - i have used noisy cricket, ruby and gems, but they are all made for "real" guitar speakers - hopefully this is the answer for small speakers

sorry about your flooding - that happened to me years ago and flooded my whole house

i'm ordering a couple of boards and am gathering up the parts online as i live in the middle of nowhere

Member for

12 years 1 month


Thu, 08/09/2012 - 21:55

Well, depends on what you mean by small speakers. I use 4 inch car audio speakers (I have some that I'd like to sell on my site, if I can ever get my shipping software to talk to the shipping scale to talk to the online web store.) I suppose on that scale, they are a lot smaller than guitar speakers.

But little teeny speakers like you'd get out of a kids toy or something, well, those are something else entirely. Generally, you want to make sure that any speaker you use can take more than 2 watts of power. If it's less than a watt, beware! I fried a .25 watt speaker in a few seconds without even realizing what I was doing.

At any rate, I hope you like it! Let me know how it goes after you have one built, okay?

rich (not verified)

Thu, 09/13/2012 - 18:39

i finally got around to wiring one of the boards i bought - plugged in the guitar - led doesn't light up and 9 v battery immediately begins to heat up - redid all solder joints - checked all components - same problem - i didn't use components from your kit cause you were out due to flood, but only change was in the .1uf caps where i used 2 mylar and 1 ceramic - used 16v 100uf electrolytic caps - and soldered chips directly to board as i was out of dip sockets

any suggestions?

Member for

12 years 1 month


Sat, 09/15/2012 - 14:54

Well, clearly there is a short somewhere.

Start at the battery. Are you absolutely sure that you have it in the right way? Before you plug in your guitar or turn it on, can you verify the polarity of the battery with a meter?

Many 9v battery holders use stranded wire; make sure that you don't have a single strand bridging your + and - terminals.

If you have it wired up so that when you plug in the jack, you are turning on the guitar, make sure you aren't doing something like accidentally shorting your V+ and your signal input (actually, I'm not sure that would jive with your symptoms, but check it anyway).

Check V+, power ground, signal in, and signal ground and make sure they are all okay, that they go where they need to and there are no shorts anywhere.

Check all the wiring around R5, R6 and C4 for solder bridges.

Check both sides of the board for solder bridges, sometimes you can flow too much solder and it will come out the other side of the board and cause problems.

Double check that you have your chips in right side up. Double check all electrolytic caps, make sure they are all in right and none of them are in backwards. If they are in backwards, you will have to replace them.

Do you have a breadboard? Get a 1k to 3k resistor, hook it up to the + terminal of a battery or power supply, hook up the other end of the resistor to the + lead on the LED, and hook up the - on the LED to your breadboard power supply. Does the LED light up? It is possible you have the LED in backwards, but I bet there is a short somewhere in your board, and the current is all going through that short, causing the battery to warm up.

Let me know if any of this helps.


Member for

12 years 1 month


Sat, 09/15/2012 - 14:55

Also, can you take a good picture of the front and back of your board and upload it somewhere? You can email it to crazybutable at if you don't have anywhere to upload it to.

Member for

12 years 1 month


Fri, 09/21/2012 - 23:34


After some back and forth over email, we figured out that the problem was that he accidentally sorted some resistors into the wrong bins. To be fair, 1.0 ohm resistors (brown black gold gold) look mighty like 100k resistors (brown black yellow gold).

R5, R6, R7, and R8 were all mistakenly soldered in with 1.0 ohm resistors instead of 100k ohm resistors. The voltage divider of R5 and R6 absorbed most of the current from the battery, fortunately. I was worried that R7 and R8 being so low could possibly blow out the op amp, but since most of the current could just freely flow through R5 and R6, it did so, not leaving enough to screw with the opamp.

Once Rich replaced the 1.0 ohm resistors with the proper value resistors, his amp worked just fine.