How's an audio probe work?

[M.D.]

What is an audio probe and what's it do?(well i have a good idea anyway)

what are good features or qualitys to look for in one?

heh and a low cost one would be cool as well.

Mike. :twisted:

[Samuel]

how does $2.50 sound for low cost? Check out the debugging page for a diagram. Basically it's a mono 1/4" jack, two lengths of wire and a 0.1 uF capacitor. It'll take you about a minute to build and you'll be PSYCHED you did.

The idea is to set up a device so that you can pull audio signal out to your amp from any point in the circuit. It's very useful for finding cold solder joints and bad components. One piece of wire ties from the ring/sleeve of the jack to the ground of your circuit (use an alligator clip to keep it there). The other piece of wire goes from the tip of the jack through the capacitor. The wire or other lead of the cap is what you use to "probe" the circuit. Simply plug the probe jack into your amp, your guitar into the input jack of the circuit, power it up and start poking connections with the cap end of the probe. It's probably not a great idea to go feeding 9V into your amp input, so watch where you put that thing! But it is fantastic for finding out how far your signal gets if the whole circuit is misbehaving. It's also extremely educational about what happens to your signal as it moves through the circuit. For example, hearing your signal before and after a transistor is very interesting as far as hearing just how much the signal is getting amplified, etc.

[aron]

Thanks Samuel!

Yep, the audio probe is really great for learning what a circuit does to your signal as it travels through the entire circuit.

[M.D.]

Wow that was easy I feel so stupid thanks guys

Mike. :twisted:

[zener]

Sorry, but I still don't get it. My Ross Compressor didn't worked as I put it in the box. As I used the Audio Probe, there were some parts where there's audio, there were some where none, just a short, mild tap sound.

How can I tell where the problem is?

Thanks

[petemoore]

I like to use a 'disposable' or replacable amp for the AP.
 Something like puter speaker and amp is perfect and 'free'....if ya look hard nuff...A little Gem does the trick fine...ie, I don't use the MkII for audio probing...
 Jest start at the beginning of the ckt [input cap] get some signal source [cheep keyboard with a key taped down?] and start poking farther into the ckt.
 Check against yer schematic...the tap off a transistor [that leads to next stage or output...etc.] always is an emitter follower or comes off the collector and should have signal in it...depending...[LFO Q's don't get 'guitar' signals]
 Opamps are similar...try the signal inputs and outputs on them too...you can skip PS connects like 9v and ground [check them with DMM beep] be sure to look at the schematic to see what should/shoul not have signal...
 COntinue further into the Ckt. till you lose signal in a place you think you should have signal ... then look around that area for the problem.

[Ed G.]

Sorry, but I still don't get it. My Ross Compressor didn't worked as I put it in the box. As I used the Audio Probe, there were some parts where there's audio, there were some where none, just a short, mild tap sound.

How can I tell where the problem is?

Thanks

You need to use the probe with the schematic. Follow the signal as it goes through the circuit. If it stops somewhere, there's your problem.

[Samuel]

Also, if you happen to own an eBow, I find this is a great companion to the audio probe. I just lay my guitar flat, lay the ebow on one of the strings, and I've got a nice constant signal for my debugging...

[Bill_F]

Also, if you happen to own an eBow, I find this is a great companion to the audio probe. I just lay my guitar flat, lay the ebow on one of the strings, and I've got a nice constant signal for my debugging...

I use a portable CD player as my signal source.

[D Wagner]

This is what you need.

http://www.talkingelectronics.com/FreeProjects/MiniBenchAmp/MiniBenchAmp.html

It is self contained, and easy to use.  Just copy the artwork to a graphics program, trace over it, and make your PCB from that.  Or construct it on perboard, using the diagram as a guide.  

I built one, and it works fantastic.  I don't have the earphone permanently attached right now, though.  I used a needle for the probe, and made mine "dual mono", so I can use headphones instead of an ear bud.

Good Luck,

Derek