Simple Active Mixer on sinlge voltage

Description: It will operate on a single supply. It has been tested with a 9-volt battery and continues to perform well with a regulated 5-volt wall adapter. A modified version with input gains is available for connecting guitars or microphones, which includes power regulation to eliminate humming when using a wall adapter. For those who prefer to use a 9-volt battery without the additional features, it is recommended to omit the LM317 along with the associated capacitors and resistors. In this case, connect the positive terminal of the battery to the line where the four 10k resistors are located, and the negative terminal to the ground.

This circuit design allows for flexibility in power supply options, accommodating both battery and wall adapter configurations. The core component, the LM317 voltage regulator, is used in the modified version to provide stable output voltage and minimize noise, which is particularly beneficial for audio applications. The inclusion of input gains in the modified version enhances the circuit's ability to interface with higher-impedance sources such as guitars and microphones, ensuring optimal signal levels are maintained.

When utilizing the circuit with a 9-volt battery, the omission of the LM317 and its associated components simplifies the design, making it more efficient for battery operation. The connection of the positive terminal to the line with the four 10k resistors is crucial for maintaining the desired voltage levels across the circuit. The four 10k resistors can be configured in various ways depending on the application, such as forming a voltage divider or providing load resistance.

The grounding of the negative terminal is essential for establishing a common reference point within the circuit, ensuring proper operation and signal integrity. This design is suitable for various applications, including audio amplification, signal processing, and experimental electronic projects, making it a versatile choice for both hobbyists and professionals.It`ll work on single supply. I`ve used it when I ran my lunetta on a 9 volt battery for a while and it`s still loud and proud running on my new regulated 5 volt wallwart. If you want one with input gains (to plug in guitars or mics), I made a modified version, also with power regulation to run off of a wall wart without humming.

If you don`t need that and just want to run on a 9v battery, then omit the LM317 and caps/resistors connected to it, and hook the + of the battery to the line where the four 10k resistors are, and negative terminal to the bottom line, which is ground: