whit3rd 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.

** Several times worse than useless.



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?

** Nope. Markings on a dial are plenty accurate.


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

Battery powered, then;

** Nope. A plug-pak supply woul be fine.




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

Or, maybe a white-noise output?


** Worse than your other mad ideas.


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.

** You may have one of them, but they are not plentiful worldwide.


I can't think of any single item that does all these

** I had to build my own ideal bench generator.

Combination of a 2Hz to 200kHz low THD oscillator, squarer circuit, 1000:1 stepped attenuator, fine frequency adjust, fixed level transformer isolated output for scope synch, another fixed output for the frequency counter.

Amplitude stabilisation is selectable between a glass bead thermistor or a
diode limiter - the latter resulting in zero bounce but 0.2% THD.

Frequency adjustment uses a log wound, double gang 15kohms WW pot - for stability and low noise.

THD of the oscillator is 0.002% and with the aid of a -100dB notch filter I can test nearly anything.



..... Phil



.... Phil