ART HD-31 (Model #350) High Definition Graphic Equalizer - Serviced Tested by DALAUDIO and found to be in good working order. The physical condition is also very good. Please see all photos. The ART HD-31 is a 1/3 octave graphic equalizer designed for professional audio applications and is suitable for both studio recording and sound reinforcement. The "31" in its name refers to the 31 bands of equalization it provides. It is a single channel (mono) high-definition equalizer offering precise control over a wide range of frequencies. We can provide a digital copy of the manual if you bring a USB memory stick. 
 
Cash Sale NO Holds Call or Text for Pick-Up 
 
A bit more detail
Graphic Equalizer allows you to visually adjust the gain of specific frequency bands using sliders, making it easy to see and adjust the frequency response. Each of the 31 sliders represents approximately 1/3 of an Octave spacing of the frequency band, offering fine-grained control over the audio spectrum or detailed frequency shaping. 
 
Applications: The ART HD-31 is commonly used in recording studios, live sound reinforcement, and other audio production environments where precise control over frequency response is required. 
 
Key Features:
Low and High Pass Filters: Low 20hz and 40 Hz (together create low filter "brickwall") or High 20Khz /16Khz (both create high filter "brickwall") -  Can be used to remove unwanted low-end rumble or high-frequency noise. 
Switchable boost/cut range: 7.5dB or 15 dB  Allows for flexibility in how many dB each frequency band can be adjusted + or -  
Level Control: Slider for signal output control +or - 15dB 
Signal and Peak/Clip Level LED indicators. 
Active or Cut relay - Signal passthrough (also on power failure)  
Connectivity: TRS In Out or barrier strip for balanced connections