- Category: Audio Projects
These were the final version of my audio level meters, used on many audio projects, including audio amplifiers and audio controllers. They have 22 LEDs arranged as two rows of eleven and could be set to display in bar or dot mode.
Sometimes when you etch your own PCBs using resist ink you can have issues such as over or under etching the board. But I hadn't expected that my failure to clean and seal the board properly after soldering wuld result in oxidation eating the board away over the course of a year until my most complex hand-etched board would fail, taking my favorite and most used / enjoyed project with it.
While building custom amplifiers over 20W I found that my bookshelf speakers were too weak to handle the power and I never test amplifiers on my good home stereo speakers so it was time to build a custom set just for testing amplifiers over 50W. The result was a modest 80W RMS 3-Way speaker system.
This is the working Prototype Power Amplifier I built around the LM3886T Power Amplifier IC. This unit was capable of approximately 85W RMS with a peak power output over 100W! This was the first amplifier I built that was over 50W as well as the first time I used this particular audio amplifier IC. This prototype would lead to several more refined versions that eventually became the amplifier I used for my DJ business.
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.
These were my own design in audio level meters. This prototype was built to test in my next prototype audio controller. This design uses the LM3916N Dot/Bar display driver chip, and measures line-level audio signals. I got the 10-segment LED bargraph displays from Radio Shack. These work GREAT on line-level audio signals and are very fluid and responsive, allowing both dot and bar modes.
For my next project I broke things up into stages. The first step was to build the power supply for the audio controller section of my next amplifier. This is a 3-way power supply for that audio controller. The various circuits within the controller required 5VDC, 12VDC and -12VDC. This supply was designed to handle all of those needs. It used 2 transformers and three voltage regulators with heat sinks.
As computer audio devices got better I felt a need for a better amplifier for my PC with more inputs so I could still have my SNES and Genesis connected. I also wanted to be able to see the level of the audio signal. This prototype had electronic input selection via four push-button switches on the front wired through logic into a special IC, the National Semiconductor LM1037N stereo audio switcher. The output of this amplifier used the LM2879 Dual 8-Watt amplifier IC, also by National Semiconductor.