Micro power amplifier for line recording

I wanted to try to make a emulator of tube power amplifier, so it can be overdriven when playing in a line or a guitar combo at low volume. Also added speaker simulator and speaker saturation emulator.

As a result, was born the following schematics and the board

With bipolar ± 12V power

Schematics (pdf)

pdf

Ready to transfer PCB (pdf)

pdf

Upper side assembly (pdf)

pdf

Bottom side assembly (pdf)

pdf

Assembled board

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With single-supply +12 V

Schematics (pdf)

pdf

Ready to transfer PCB (pdf)

pdf

Upper side assembly (pdf)

pdf

Bottom side assembly (pdf)

pdf

Some comments to the schematics:

Potentiometer P1 is used to set quiescent current (with no signal) of 2 mA for each output transistor. Potentiometer P2 used to set the desired level of speaker saturation.

To the connector J2 are connected "Presence" and "Depth" controls:

pdf

Output signal Limitation

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Samples:

Clean (minimum saturation)

Overdriven (minimum saturation)

Clean (middle saturation)

Overdriven (middle saturation)

Clean (maximum saturation)

Overdriven (maximum saturation)