[Almost] free DIY audio probe

[Ed Nice]

I was thinking an audio probe would be a nice addition to my toolsbox. There are a ton of examples on the internet, so what they do and how to make one is pretty simple, but I was thinking of the hassle (I'm lazy) of an input signal and having to use the guitar amp. What a bind.

I downloaded a tone generator for the phone, so that solves that. So I need to get the signal out of the headphone socket into the effect input.. blah, blah...

Anyway, I was having a mooch and I spotted a set of old PC speakers.

a. They are a small amplifier
2. They have a small stereo jack on the end.
iii Bingo...

Anyway, after I got back from Bingo, I made my audio probe in true McGuyver fashion, in about 40 minutes.

Dead simple.

I cut the phono lead in half. Soldered the bit with the phono plug on to a mono jack. Soldered a bit of wire onto the shield of the end attached to the speakers, soldered a 1uf cap onto the other two leads, taped it up, one shiny audio probe.

So, for anyone wanting the build list (there are other n00bs like me out there you know!):

An old pair of amplified P.C. speakers with a small stereo jack
FuncGen or similar on the iPhone/Android to generate a tone
1 x 1uf electrolytic capacitor
A cocodile clip
A few inches of spare .22 wire

Here's how she looks...





The small geen plug is the stereo socket for the signal, ie, the headphone socket on the phone. I had to use the phone to photograph it, so...  

I know this isn't really that exciting, but it's recycling and is a lot less messing around that having to send output to the Marshall stack and play and probe :)  

[AC_FX]

Good idea.  I'd already built a tone generator and have a small bench amp, so when I made my audio probe I just did it the normal way.  It never occurred to me to use the iPhone and computer speakers that were also hanging out on my bench!

[Suzukiscottie]

Satisfaction level soaring! :-)

[Ed Nice]

I've had a bit of a prod and a poke now. It makes various noices at various places so it's working really well, but I'm not really savvy enough about the whole circuit thing to know what to check for where, so I'm going to read a few articles and stuff to see what's what.

I'm probably prodding stuff I should really avoid, because I know there is the audio signal and some power to various things and I'm probably shorting stuff out that is best left alone.

My victim/test is a Little Angel Chorus that's working, but the chorus sound is really subtle, so maybe I can figure out where I can pep it up a little (or more likely, what I've put in the wrong place).

A little (and I mean little) knowledge is surely a dangerous thing...