Audio Probe Question

[toneless]

I just made my first audio probe (that I found at geofex.com) and I’m really satisfied with it.
I wanted to know if I can use something like this for fixing tube amplifiers and what parts I’ll have to change.

Thanks

I suggest to anyone that doesn’t have one of these to try it out…

[Peter Snowberg]

All you need to change is to increase the voltage rating of the cap to 600 volts.

I would suggest one additional change however. If you add two zener diodes with opposite polarity and in series between the amplifier side of the cap and ground, you will limit your amp's exposure to voltage spikes above 16 or so volts.

If you do all your tracing with a tube amp you don't have to worry about voltage spikes, but if you do this with a solid state amp that doesn't have good input protection you could easily blow it out if you don't include something to clamp the voltage.

Take care,
-Peter

[yano]

Peter, I wouldn't mind seeing a schematic of that, if you could, heheh.

[Peter Snowberg]

OK, how about this:



I added a current limiting resistor too. You could use a wide variety of values for any of the parts. The cap should be a 600V unit, but it could be anywhere from 0.22uF down to 0.01uF. The resistor could be anywhere from 100 ohms to 100K. The Zeners could be anywhere from 5.1V to 15V. These values are very general.... you could easily go outside them. I would just recommend keeping the cap working voltage at 600V and don't make the zeners too large or your amp may not like it. 9.1 Volts is probably about the best value as will limit anything your amp sees to less than 10 volts.

Take care,
-Peter

[yano]

good deal!