Adjustable Parametric Equalizer Proposal, Study Guides, Projects, Research of Engineering

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Adjustable Parametric Equalizer

Proposal

Adam Grunke October 30, 2003 ETEC 471 Professor Morton

Introduction The Adjustable Parametric Equalizer (APE) allows the professional audio engineer to select and adjust a frequency using a single knob. With a 31 band graphic equalizer (EQ) which is the most common method of equalization in sound reinforcement, the entire audio signal will be passed thru 31 filters and then be summed together. With the APE, the audio signal will only pass thru five filters. One of the filters is a band pass filter for anti-aliasing purposes. The remaining four can be used as a high pass filter (HPF), low pass filter (LPF), notch filter (NF) or a narrow band pass filter (NBP). The current settings will always be saved so that they won’t be lost when the unit is powered down. The APE will be used for live and studio sound applications: equalization of the main stereo mix out of a sound console, two separate monitor mixes, equalization of two different instruments, or as a crossover.

Description The APE will have both a dual XLR and ¼” Phono jack for inputs (Figure 1.). This allows the APE to be used with a variety of high end systems quickly and without any adaptors that could introduce problems. The signal will then go through an audio band pass filter. The low frequency roll off will start between 20 Hz and 25 Hz and the upper frequency roll off will be around 20 kHz. The audio will then go through a series of audio filters. The APE will have one knob (Figure 2.) that will allow the user to adjust the frequency of the filter. After pushing on the knob the gain of each filter will be controlled by a digital potentiometer (Figure 3.). Once the adjustment has been made, the knob is pressed again and the frequency of the next filter can be adjusted. To re adjust a filter, the user would press the knob a number of times until the desired filter is selected. A representation of the equalization will be displayed on a text LCD. When

Project Development and Demonstration To design and test the hardware I will be using the equipment in ETEC 340. I’ll use Eagle to design a circuit board for the final design. I will run a frequency sweep into the input and then display the output on a spectrum analyzer to demonstrate the APE. As the user adjusted the gain of each frequency, the changes will be seen on the spectrum analyzer and the APE’s display.

110 V ¼” In Stereo XLR InStereo XLR OutStereo ¼” OutStereo (^) ON/OFF Switch

Figure 1. Rear Conceptual Sketch

ON/OFF LED Display^ Single Knob Control

Figure 2. Front Conceptual Sketch

Left (^) AliasingAnti- AudioFilter AudioFilter AudioFilter AudioFilter LeftAudio Audio Input Output

Knob MCU controlling filtersand the LCD^ DisplayOutput

RightAudio Input Aliasing Anti- AudioFilter AudioFilter AudioFilter AudioFilter RightAudio Output

Figure 3. Block diagram of EQ