This is my very very old audio preamplifier based on the TDA1524 Integrated Circuit.
For many years it has provided volume and tone control to an old amplifier I built when I was still a secondary school student.
The whole schematic was based in the reference circuits from the datasheets.
This is the base schematic for the tone and volume controls from the TDA1524 datasheet:
I added a VU-meter to the box where the circuit is assembled, based on a Sanyo LB1403 IC. This is also the reference schematic and it works very well:
The power supply uses a 7812 voltage regulator with a large filtering capacitor and powers both circuits. It's not shown here.
Unfortunately the PCB was design in Tango2 a very powerful and also very old CAD software for MS-DOS and I have no idea were my floppies and pcb files are! So no PCB for this one!
I have some pictures of the box. Please ignore the messy wire installation inside the box:
The volume and tone controls work very well. The VU-meter needs calibration prior to use but that is very simple to do. Just input some sine signal with 0.707V and adjust both channel trimmers in the VU-meter until the 0dB LED lights (LED at pin 3).
Some datasheets of the main components: