This is the beginning of a newer type of amplifier I started building in 1994. This prototype audio controller uses the power supply and audio level meters mentioned in previous projects. It is designed to be half of a two-part system in which the audio signals from all your devices come into a central audio controller. Here the signals are processed and controlled and then fed into the other part of the system, which is the power amplifier.
In this photo you can see I have milled out the Prototype cabinet and installed the front and back panel parts. Inside the cabinet I have also installed the power transformers and power supply board, and the main control board is being fitted for drilling, but nothing is wired together. Notice my Prototype Audio Level Meters are used in this project, as is the Prototype Audio Controller Power Supply. You can see in the photo that there are four stereo inputs as well as a separate tape monitor section and finally the output to the Prototype Power Amplifier.
At this point I have completed the main board and installed it. I have also wired all the sub-assemblies together, and the unit is now ready for testing.
This is just a better look at the front panel. As you can see, audio input selection is made via a control knob. However, the actual switching of the stereo signals is being done by the LM1037N audio switcher IC. From left to right there is a power switch, power LED, level meters, selector knob, selection LEDs, tape monitor button, tape monitor LED and volume control knob.
This unit worked great for about a year, but then started doing some strange things. The problem was eventually traced to some issues with oxidation of the traces on the Prototype Audio Controller Main Board and the unit was eventually decommissioned.