Function generator or Audio generator?

[sawdust]

I am looking at getting either a function or audio generator. Which one would be best for guitar amp work. I know I get more features out of the function generator but just an audio one is cheaper. Would you just use a sine wave for testing amps or do you need the square wave, sawtooth signal as well?

Dave

[tubesornothing]

A couple of things I looked for:

- really low harmonic distortion (useful if you like to see what harmonics a gain stage is adding)
- programmable sweep is cool for looking at tone stacks and filters (if you have a FFT scope or computer)

other than that I mostly use sine wave, sometimes used triangle, but not too often.

[PRR]

Are there any true sine oscillators left?

The bulk of the market must be function generators, they are SO much cheaper. Or not-cheap and far more versatile.

The sine on an affordable funcgen is always nasty. The basic waveform is the triangle, and the square used to flip the tilt to make the triangle. The "sine" is made by rounding-off the tops of the triangle. At best, it is not very good. A true sine sounds mellow, even unnaturally hollow. A funcgen "sine" has tip-pips and many small high overtones.

> Which one would be best for guitar amp work.

Doing WHAT to guitar amps?

Basic checking? Precision measurement? Tweaking?

The funcgen will prove that signal goes through, that it is even (or not) at all frequencies (assuming no very-sharp filters, which is usually true for guitar amps), and amp-type distortion can be easily seen/heard despite the funcgen pips. It is small, cheap, stable.

The triangle is very handy for checking clipping level. When you flatten the top of a sine, it is hard to see, especially with the soft-clip of tubes. The top of the triangle is a distinct angle, and you can see very slight clipping.

Square is a classic way to get a sense of both low and high frequency droop at once, but needs some experience to interpret. It can cook load resistors.

Most meters are calibrated "sine RMS", really read average or peak, and will NOT give correct readings on a triangle.

Nothing beats the ambiance of a 1957 H-P 200AB. Sine-only, and bobbles when you sweep it, but the dust on the tubes reminds you of History.

[tubesornothing]

The triangle is very handy for checking clipping level. When you flatten the top of a sine, it is hard to see, especially with the soft-clip of tubes. The top of the triangle is a distinct angle, and you can see very slight clipping.

...cool...