On Monday, December 29, 2014 4:32:20 PM UTC-8, Phil Allison wrote:
**Hi,

what specs does an audio generator need to make it ideal for servicing guitar amps?

In the 'convenience' category, consider an iPod with a few recorded test tracks.

1. Ability to adjust the output level to well below 1mV and smoothly up to several volts.

Probably that means you need calibration of the output, too? A ten-turn pot and a
trueRMS meter would be helpful.

2. Circuitry not linked to the AC safety ground to avoid hum loops.

Battery powered, then; the iPod and an old HP204C (Wien bridge) generator would fit.
Or, anything with a good signal-level transformer.

3. Have a fixed level output to connect to the external trigger input on a scope - so the trace remains in synch despite noise, hum and harmonics.

Any generator, with an external attenuator, will do that.

3{a}. Square wave output for checking tone circuits and amplifier stability.

Or, maybe a white-noise output? Mainly, (3) and (3a) will require an arbitrary waveform
generator, nowadays; other sine/square combos are mainly inaccurate.

4. Frequency from 10Hz to 100kHz, preferably in four overlapping ranges.

Arb or HP204 will qualify.

5. Amplitude remains steady when frequency setting or range is changed.
Arb should do that.

6. THD not more than 0.1% with low order harmonics.

After warmup, the HP204 will do that. Or, an expensive arb. Or, a good CD player.

I can't think of any single item that does all these (but simple, easily
available equipment can do any of 'em).