On 13/03/2017 09:32, Jasen Betts wrote:
On 2017-03-13, wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).
I mainly want this to run thru an amplifier to listen to the frequency
repsonse of the amp and speakers. Nothing very scientific, just to see
what these amps and speakers can do.... And on occasion to inject an
audio signal into amp sections to dee if the audio is passing that
stage.

Any reason you've not looked at PC software?

Indeed. I favour Daquarta (sp?) for this sort of thing.

The paid for version will even give you a realtime FFT vs time waterfall
plot of the input signal and the signal generator part continues to work
after the evaluation period. It can do the usual waveforms well enough
for all but the most demanding tests.

It is easily good enough for most audio work and allows you to see
harmonic content of signals in realtime. The only disadvantage is that
it perhaps isn't going to like mains voltages on the inputs/outputs of
your PC so you would need to be careful.

My search on ebay lead me to something called a "Function Generator".
What the heck is that??? And also called a DDS device. (I have no clue
what DDS means).

look it up on wikipedia. it means that inside there's some sort of computer
generating a digital wavform, that gets converted and comes out the output

There used to be old school analogue function generator chips that made
a triangle wave and then applied diode shaping to get a pseudo-sine
wave. HP made one design implementation that was surprisingly good.
Intersils 8038 was the poor mans alternative for DIY.

http://www.intersil.com/content/dam/...l8/icl8038.pdf

These days DDS is probably the way to go since it can do so much more.
Testing power amps it is wiser to use frequency shaped noise rather than
pure sine waves since you can hit mechanical resonances and damage
acoustic drivers with quite modest power levels of pure sine wave.

--
Regards,
Martin Brown