ART HD-Series Graphic Equalizers

Introduction

The ART HD-Series of Precision Graphic Equalizers are designed for superior audio performance and functionality. They offer precision frequency tailoring, reliable performance, rugged design, and silent processing, making them ideal for various audio applications.

Key Features

• Active Filter Sections: Constant-Q design with precise center frequencies and narrow bandwidths for minimal filter interaction.
• Precision Slide Potentiometers: 20mm center-detented faders positioned on ISO center frequencies.
• Independent Variable Hi and Low Pass Filters: Allows custom tailoring of the audio signal with separate controls for high-cut and low-cut filters.
• Automatic Relay Bypass: Ensures audio signal continuity if power is lost.
• Additional Controls: Variable input level, clip level indicator, ground lift switch, selectable line voltage.
• Selectable Scale Switching: +/-6dB or +/-12dB gain range.
• Multiple Connectivity: XLR, 1/4" phone, and Euroblock connectors.
• Durability: Rugged construction suitable for rack mounting (1U for HD131/HD215, 2U for HD231).

Safety Instructions

Important Safety Information:

• ⚠ Caution: Risk of Electric Shock - Do Not Open. Internal components are not user-serviceable. Refer servicing to qualified personnel.
• ⚠ Warning: Uninsulated Voltage. The symbol indicates the presence of dangerous voltage inside the enclosure.
• ⚠ Read Manual. The symbol indicates important operating and maintenance instructions.
• Power Sources: Connect only to the specified mains power type with a good ground connection.
• Power Cord: Use the provided cord. Ensure it is not likely to be walked on or pinched.
• Grounding: Do not defeat grounding or polarization features.
• Moisture: Do not expose to moisture or use in damp conditions. Do not place liquids on the unit.
• Heat: Avoid direct sunlight and heat-producing equipment.
• Environment: Protect from excessive dirt, dust, heat, and vibration. Avoid smoke and spillage.
• Handling: Use adequate padding for transit. Lift carefully to avoid injury or damage.
• Servicing: Unplug the unit if exposed to moisture, damaged cord, or unusual noise/odor. Refer to qualified personnel.
• Installation: Follow user guide instructions.

General Information & Installation

These equalizers are designed for professional audio applications requiring precise frequency adjustment. They are built for rugged use and are suitable for fixed installations and touring sound systems.

Installation: Units are designed for standard 19" equipment racks. Vertical height is 1.75 inches (1U) for HD131 and HD215, and 3.5 inches (2U) for HD231. Depth is 7 inches.

Connectivity

Power Connectors: Internal power supplies operate on 120 or 240 VAC, 50-60Hz. Ensure correct line voltage setting before connecting.

Input/Output Connectors: Each unit features three sets of parallel input/output connectors: XLR, 1/4" phone, and Euroblock barrier strips. Use only one input per channel.

• XLR: Balanced, Pin 1=Ground, Pin 2=High (+), Pin 3=Low (-).
• 1/4" Phone: Can be used balanced or unbalanced. Balanced: Tip=High (+), Ring=Low (-), Sleeve=Ground. Unbalanced: Use a mono cable, which grounds the ring to the sleeve.
• Euroblock: For secure wire connections.

Signal Levels & Grounding

Signal Levels: Normal levels are -10dBu to +4dBu. Maximum levels are approximately +22dBu (balanced) or +16dBu (unbalanced). Microphones and instrument pickups typically require a preamp to reach line level.

Chassis Grounding: Equipped with a rear panel Ground Lift switch. Set to 'Ground' by default. If hum or buzzing occurs due to ground loops, experiment with the 'Lift' position. Note: Always turn amplifiers down before changing grounds.

Operating Instructions

Bypass Switch: When activated (red Bypass LED illuminates), signal passes directly through the unit at unity gain, allowing comparison of equalized vs. unequalized audio.

Range Selection: Switchable gain range: +/-6dB (green LED) or +/-12dB (yellow LED).

Level Control: Adjusts output signal level (off to +6dB). The red Clip LED indicates signals near clipping (within 6dB). Occasional flickering is normal; a steady LED indicates the need to reduce level.

Initial Set Up Tips:

1. Set channel output levels to center detent (0dB).
2. Engage Bypass switch (red LED on).
3. Set frequency sliders to center detent (0dB).
4. Set Hi Pass filter to 10Hz and Low Pass filter to 40kHz.
5. Select +/-6dB range (green LED on).
6. Apply signal; if Clip LED is on, reduce input signal.
7. Disengage Bypass switch (red LED off).
8. If Clip LED is on, reduce Output Level control.
9. Begin equalization.
10. If more control is needed, switch to +/-12dB range.

Front Panel Controls

1. Power Switch: Turns the unit ON/OFF. CAUTION: Turn equalizer ON before power amplifiers, and OFF after power amplifiers.
2. Filter Level Controls: Sliders for each frequency bandpass filter. Center detent for flat response.
3. Filter Range Switch & Indicators: Selects +/-6dB (green LED) or +/-12dB (yellow LED) gain range.
4. Bypass Switch & Clip Indicator LED: Bypass switch routes signal directly to output (red LED on). Clip LED (red) illuminates when signal is near clipping.

Filter Controls

1. Hi Pass Filter (Low-Cut): Adjusts roll-off frequency from 10Hz to 250Hz. Used to reduce unwanted low frequencies, hum, and rumble.
2. Low Pass Filter (High-Cut): Adjusts roll-off frequency from 3kHz to 40kHz. Used to reduce unwanted high frequencies and noise.
3. Level Control: Adjusts output signal level. Set for unity gain by matching levels when toggling bypass. Ensure signal levels remain consistent to avoid unexpected volume changes.

Rear Panel Controls & Connectors

1. Power Cord: Connects to AC power source. Ensure the grounding pin is not removed.
2. Fuse Holder: Contains the primary AC fuse (0.5A for 95-125VAC, also for 220-240VAC). Replace with the same type. Check fuse holder orientation for correct voltage.
3. Ground Lift Switch: Disconnects signal ground from mains/chassis ground to minimize hum caused by ground loops.

Applications

Graphic equalizers are used to modify the frequency contour of sound systems for problem-solving or creative purposes.

• Typical Reinforcement: Mixer -> EQ -> Power Amplifier -> Speaker.
• Mixer Signal EQ: Mixer (Send) -> EQ -> Mixer (Return).
• Instrument EQ: Instrument -> Preamp -> EQ -> Amplifier.
• Effects Loop EQ: Preamp -> Stereo Effects Loop -> EQ -> Amplifier.

Specifications

Warranty Information

Applied Research and Technology (ART) provides a limited one-year warranty for this product against defects in workmanship and materials from the date of purchase. ART will repair or replace defective parts at its option. This warranty excludes misuse, abuse, or unauthorized alterations. For units purchased outside the United States, service is provided by authorized distributors.

Service Information

If your unit requires service:

1. Verify the unit is the cause of the problem and all connections are correct.
2. If the unit is at fault, document the problem and your setup.
3. Contact Customer Service at (716) 297-2920 for a Return Authorization (RA) number. Service hours are 9:30 AM - 5:00 PM Eastern Time, Monday-Friday.
4. Pack the unit securely, preferably in its original carton, inside another shipping box. Print the RA number and return address clearly on the outside.
5. Include a return shipping address (no P.O. Boxes), a copy of the purchase receipt, a daytime phone number, and a problem description with the unit.
6. Ship to: Yorkville Sound, 4625 Witmer Industrial Estates, Niagara Falls, New York 14305, ATTN: REPAIR DEPARTMENT.