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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.

Originally I was looking at some of the old tube gear, such as the Eico
model 377. I also looked at the Heathkit IG-18 a transistorized version
from the 70s. Because I like that old test gear, I'd be happy to get
either of these, or another similar. Both of these are Sine and Suqare
Wave. But what I am finding is the prices combined with high S+H fees,
make these things very costly, and I have not found any of them which
claim to work. Sold as-is, for parts or repair. So, I may end up paying
$60 or more and getting something that dont work, likely needs new caps,
and so on..... If they were $25 or less, I'd take a chance, but not for
that kind of money.

For the price you might as well get a function generator. Most of the
audio type signal generators put out sine waves and some square waves.
The function generator can put out those and many other waveformes. I
have one of the China function generators that lets me hook it to a
computer and any kind of waveform I can draw on the computer screen, the
generator will put out.

The one I have will go from below audio to about 25 MHz. They make some
other models that only o to about 6 MHz for a few dollars less. It is
dual chanel so you can put signals into a stereo if you want to. Each
chanel can be set sperate. It includes a frequency counter so you can
input a frequency and see what it is. I am not sure how accurate it is
above the audio range. There is no difference in audio and RF as far as
to what you get out, just the range of frequencies, so you can use it as
an rf signal generator if you want. They are not shielded being in a
plastic case.

The waves other than a sine wave starts to degrade above about 1 MHz.
There is a modification that is on youtube that I made to mine to help
that out. You probably would not want to try that as it involves
changing about 6 or 8 of the SMDs, but the parts were less than $ 20
from one of the larger companies. I did it mainly to see how it would
work and am learning how to work with the SMDs.

There are some vidios on youtube about this one and probably others.

http://www.ebay.com/itm/DDS-Dual-cha...rce-Generator-
Arbitrary-Waveform-200MSa-s-25MHz-W9U7-/162074779152?
hash=item25bc68de10:g:CwgAAOSw74FXOayX