A portable tone generator that outputs mic level signal can be put to a number of good uses- to make quick work of sorting out long cable runs, troubleshooting cables on the fly, even as a rudimentary test device for your latest preamp build. Using a circuit provided by Rod Elliott of Elliott Sound Products, a DIY tone generator can be both simple to build and affordable.

Microphone Circuit Test Oscillator Features:

• Utilizes one dual-opamp (1458, 4558, or LM358)- one stage for the oscillator, the other as an output buffer
• Oscillation achieved via a simple resistor-capacitor phase shift network; tunable via potentiometer (R1 in the above schematic)
• Unaffected by phantom power
• Very low current draw (operates off 9V battery)

Price:

• $20.80 in components, not including enclosure

More Information:

• View Mouser project file containing the needed components
• Full details and circuit theory on ESP’s web page