Test Generator (should I?)

[mattnj]

Does anyone have any ideas for a test generator that has multiple level outputs and multiple impedance outputs?
Is something like this even necessary?

I'd like to have a simple oscillator of varying frequency (could be sine or square) that I can test my circuits with. I'd like it to have a balanced "mic" output, balanced line level output and an unbalanced "instrument" output.

I don't fully understand input vs. output impedances, so does this matter? I have an unbalanced signal generator that I have been using to do simple tests and I have been varying the level of the output to mimic different signals, but does impedance matter?

Thanks.
-Matt

 

[JohnRoberts]

Source impedance matters for measurements. The old test set I designed I standardized on 50 ohm source impedance (actually 51 ohm resistor).

For low noise measurements like for mic preamps it's often useful to make a custom pad where you can manage both source impedance and levels.

JR

 

[SSLtech]

What he said. :thumb:

Keith

 

[mattnj]

can I use a simple balanced t pad(h pad) for this?

 

[Samuel Groner]

From your first post in this thread I read that you don't want to make any measurements but to simply test your circuits for basic functionality, i.e. to check if they pass signal. For such stuff you don't need to worry about source impedance.

Samuel

 

[mattnj]

"From your first post in this thread I read that you don't want to make any measurements but to simply test your circuits for basic functionality, i.e. to check if they pass signal. For such stuff you don't need to worry about source impedance. "

OK. Thanks. I thought so.

 

[mikep]

if you are interested in measuring the input impedance of a circuit it is useful to be able to change the source impedance of your generator with the flick of a switch. this is practically the only reason I ever change my generator from 150 to 600 ohms. you have to do a little calculation, but I find this much easier than the other methods.

mike p