DIY Two-Tone Audio Oscillator
After I got my oscilloscope, I had a need for some sort of device
that would generate an audio tone so I could test various guitar
FX circuits. This little circuit fits the bill.
Since I won't be stepping on this thing with my foot like a
stompbox, it can go into virtually any kind of metal enclosure.
As I typically do, I designed a PCB for the circuit. I used a
little Whitman Chocolates sampler tin to put this circuit in. I
drilled it out as required and spray painted it, and put some
labels on it so I can keep track of what does what.
The BC548 transistor may be substituted with a 2N2222, 2N3904,
2N4401, NTE123A or other NPN transistors. The BC548 is a low
current NPN transistor with a typical Hfe of around 130. I
substituted these with 2N2222's which had an Hfe of around 175. I am using an AC adapter to power it, the jack is on the side
opposite of the controls, and I used a center-off SPDT switch to
power it up. The PCB is mounted on some 3/8" high
stand-offs. The level control is a mini-pot. The output jack is
just an open circuit mono 1/4" jack.
