Tesseract Guitar Practice Amp

Description

The design given here - which includes a complete PCB design and Bill of Materials - is highly flexible and allows the several options in both the build and use of the amplifier.

As well as a clipping circuit that some other designs - such as the more well known Smokey, Little Gem, Ruby and Noisy Cricket - have incorporated, Tesseract has several unique effects features designed into it

Details

The EasyEDA "Tesseract" DIY Guitar Practice Amplifier is an LM386 based low power amplifier designed to deliver up to about 500mW into an

8 Ohm speaker when run from a 9V battery.

Tesseract can be heard on YouTube here:

https://youtu.be/9XzodyefyV8

The design given here - which includes a complete PCB design and Bill of Materials - is highly flexible and allows the several options in both the build and use of the amplifier.

As well as a clipping circuit that some other designs - such as the more well known Smokey, Little Gem, Ruby and Noisy Cricket - have incorporated, Tesseract has several unique effects features designed into it:

Selectable Bipolar or Junction FET input stage for different input overload effects;
Adjustable gain and clipping 'hardness' in the Distortion stage;
An adjustable fullwave rectifier stage, driven by the distortion output, that generates a type of fuzz and frequency doubling effect called 'Wreckage';
An optional low frequency oscillator stage to sweep the Wreckage effect;
A simple mixer to blend the 'Wrecked' and the 'Distortion' outputs;
Selectable, adjustable low or high frequency boost (a type of tone control);
An important aspect of the design is that all the features and FX can be tweaked for your delight and delectation.
Most features are also optional and can be wire linked out if not required without affecting the other functions.
The design could easily be modified to suit the LM380 2.5W or LM384 5W amplifier chips (although the Boost function would have to be omitted) or a range of other devices.
The design also includes a headphone output jack.
The PCB includes dual footprinting to simplify the choice of some of the components.
All parts (excluding the PCB) are available from: http://www.bitsbox.co.uk/
(Bitsbox can also supply suitable small switches, loudspeakers and battery holders or clips.)
An alternative for J1 as an MPF102 is available from: http://www.tandyonline.co.uk/components/semiconductors/transistors/mpf102-jfet.html
Simulations of the different stages of this amplifier - and a copy of the EasyEDA LM386EE spice model used in them - can be found here:

https://easyeda.com/example/Tesseract_Guitar_Practice_Amp_simulation_files-H0ca8IFDB

The project was designed and simulated entirely in EasyEDA and Tesseract PCBs can be ordered direct from EasyEDA by forking the project:

https://easyeda.com/example/Tesseract_Guitar_Practice_Amp-MjP71jBni

Files