Oscilloscope coming soon - please help! From Dumble forum

[rogb]

I have had some good pointers from the Dumble guys but any more insights into a simple way to give an amp a run through on the scope would be great!

Guys I have ordered a PC-USB o/scope. I have got a bunch of 50w resistors on their way from good ole China for the dummy load.
I have looked at XYZ of O/sopes.
I have read all the threads here.
I have looked at You Tube.


Assuming I have learned to set the scope up from the info available, please explain in a simple way how to go about testing one of our style amps for oscillation and general fitness tests. Andy F was going on about 2nd order harmonics in the PI, how for example would you test for this?

I am really trying to advance my knowledge, I would really appreciate your help.

I am drowning in the snowstorm of internet information.

Thanks
Rog

[xtian]

Hi! Wow, who deleted our posts?

[Jana]

Random thoughts.

A square wave function on your signal generator is also useful to have.

The first thing you could do is to take an amp that you know is good and healthy and snoop around in it. Feed a 100mv signal into the input and probe in various places in the signal chain to get an idea of what happens.

Vary the gain controls (keeping the 100mv signal at that level) and observe how the different stages clip and what happens to the signal. Play with the tone controls to see how that alters the signal shape. A square wave is especially useful for seeing the effects of the tone controls.

Doing the aforementioned will give you a sense of what you should be seeing in an amp.

Also be aware that the sine wave may not be perfect as it goes through the amp. Treble peaking caps, for example, will alter the sine wave from its perfect shape.

Oscillations in an amp turn up in various ways on the scope depending what kind of oscillations they are. You might see a smaller wave signal riding on a part of your normal test signal.

[rogb]

Hi! Wow, who deleted our posts?

Don't worry dude, I just cast the net a bit wider

[rogb]

Random thoughts.

A square wave function on your signal generator is also useful to have.

The first thing you could do is to take an amp that you know is good and healthy and snoop around in it. Feed a 100mv signal into the input and probe in various places in the signal chain to get an idea of what happens.

Vary the gain controls (keeping the 100mv signal at that level) and observe how the different stages clip and what happens to the signal. Play with the tone controls to see how that alters the signal shape. A square wave is especially useful for seeing the effects of the tone controls.

Doing the aforementioned will give you a sense of what you should be seeing in an amp.

Also be aware that the sine wave may not be perfect as it goes through the amp. Treble peaking caps, for example, will alter the sine wave from its perfect shape.

Oscillations in an amp turn up in various ways on the scope depending what kind of oscillations they are. You might see a smaller wave signal riding on a part of your normal test signal.

Very useful random thoughts thank you