signal tracer

[davebolden44]

just wondering if anyone here uses a homemade signal tracer for troubleshooting. I was reading about this in one of Gerald webers books, he said he made his out of some high impedance headphones. was thinking of doing this as a cheap project to keep me busy while I wait for my amp kit to arrive. is it worth my time or not?

[dorrisant]

Worth it... You may not need it yet, but if you do you will already have it. Makes it so much easier to find out where things go wrong.

Tony

[davebolden44]

Now when you say high impedance headphones what are we talking and how critical is that cause I have a pair of ten dollar 32 ohm headphones I could sacrifice for this. Just don't want to go deaf or electrocute myself or something.

[ampgeek]

I am not familiar with the headphone approach unfortunately.

But..I am a big advocate of the signal tracing approach shown about 2/3 of the way down the page here:

http://el34world.com/Hoffman/tools.htm

It plugs into a known to be functioning amp as the monitor. The amp under test is loaded up with a passive load as opposed to a speaker.

Note that the 1 meg pot will place an additional load in parallel with the point in the circuit that is being tested. That may...or may not change the results. Putting a switch between the pot and ground will give you the best of all worlds.

It is the best tool in my tool box!

Rock on,
Dave O.

[davebolden44]

Very cool stuff. Where can you find an adjustable dummy load like that. That seems like it would come in very handy.

[dorrisant]

Now when you say high impedance headphones what are we talking and how critical is that cause I have a pair of ten dollar 32 ohm headphones I could sacrifice for this. Just don't want to go deaf or electrocute myself or something.

Sorry.. never built one like that. I made one similar to what Dave posted.

[R.G.]

See:
http://www.geofex.com/FX_images/audioprb.gif

You might also like:
http://www.geofex.com/FX_images/xform_test.gif

[R.G.]

Forgot to mention:
For signal tracing, you often need a signal.

Here's one:
... uh, apparently that file is gone from my page. I'll go see if I can find it. It's a one-transistor oscillator that makes a test tone suitable for running into an amp input.

And here's a fancier one that makes individual notes - kind of.
http://www.geofex.com/FX_images/Fake%20 ... llator.pdf

[labb]

R.G. I use the audio probe as a signal injector. Plug it into a walkman and can inject the signal anywhere in the signal path you want to. Have found several problems this way. Thanks for putting it out there.

[terryrocks]

I made one of these for lower voltage projects like 500 series preamps.