Lindell Audio 500 Series

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Summary

PeQ-501 a Features

The Infamous Low-End Trick

Anecdote about boosting and attenuating low frequencies simultaneously for a flattering EQ curve.

Basic Use

Low-Frequency Controls

Details on controls for low frequency adjustments: CPS, Atten, and Boost.

High-Frequency Controls

Details on controls for high frequency adjustments: KCS, Atten Sel, Bandwidth, Atten, and Boost.

The Lindell Audio PeQ-501a is a 500-series equalizer designed to provide extensive tonal shaping capabilities, drawing inspiration from classic EQ designs. It features a transformer-balanced output and is built around a vintage 1731 op-amp, utilizing hand-wound inductors and all-switched rotary controls for precise adjustments. The unit offers a real hardware bypass, ensuring signal integrity when the EQ is disengaged.

Function Description

The PeQ-501a is a program equalizer, allowing users to sculpt the frequency content of audio signals. It provides both low-frequency and high-frequency equalization with independent boost and attenuation controls. The low-frequency section focuses on the left side of the control panel, while the high-frequency section is on the right. A unique feature is the ability to simultaneously boost and attenuate on the low frequencies, a technique historically known to create a very flattering EQ curve, particularly for kick drums. The unit includes an EQ on/off switch for convenient comparison of processed and unprocessed signals.

Important Technical Specifications

Power Requirements: +/-16V
Input Impedance: 2.4 kΩ, op-amp balanced
Output Load Impedance: 70 Ω transformer-balanced
Frequency Response: +/-1dB 20 Hz to 20 kHz
Dimensions:
- Width: 76 mm (3")
- Height: 178 mm (5.25")
- Depth: 229 mm (9")
Weight: 1.47 kg (3.25 lbs)
Extended High Frequency Range: 1K, 1.5K, 2K, 3K, 4K, 5K, 8K, 10K, 12K, 14K, 16K
Extended Low Frequency Range: 20Hz, 30Hz, 60Hz, 100Hz, 150Hz
Internal Components: Transformer balanced output, vintage 1731 op-amp, hand-wound inductor, gold-plated PCB internals.

Usage Features

The PeQ-501a's controls are intuitive and comprehensive:

Low-Frequency Controls (left):

CPS (Cycles per second): This switch sets the operating frequency for both the low-frequency Boost and Atten controls. Available frequencies include 20Hz, 30Hz, 60Hz, 100Hz, and 150Hz.
Atten: This rotary control adjusts the amount of low-shelf cut applied at the frequency selected by the CPS switch. The range is from 0 to 10.
Boost: This rotary control adjusts the amount of low-frequency boost applied at the frequency selected by the CPS control. The range is from 0 to 10.

High-Frequency Controls (right):

KCS (Kilocycles per second): This switch sets the operating frequency for the high-frequency Boost and Atten controls. Available frequencies include 1K, 1.5K, 2K, 3K, 4K, 5K, 8K, 10K, 12K, 14K, and 16K.
Atten Sel: This switch specifically sets the operating frequency for the high-frequency Atten control. Available frequencies include 4K, 8K, 12K, 16K, and 20K.
Bandwidth: This control adjusts the Q (width) of the frequencies affected by the high-frequency Boost control. Turning it left results in a "sharp" (narrower) Q, while turning it right results in a "broad" (wider) Q.
Atten: This rotary control adjusts the amount of high-frequency attenuation applied at the frequency selected by the Atten Sel control. The range is from 0 to 10.
Boost: This rotary control adjusts the amount of high-frequency boost applied at the frequency selected by the KCS control. The range is from 0 to 10.
EQ: This switch turns the unit's equalization on or off. The manual notes that the unit is "more fun when set to 'on'."

Installation:

Power off the 500-series rack.
Ensure no obstructions around the card edge connector.
Carefully slide the PeQ-501a into an empty slot.
Ensure the edge connector is securely installed.
Install screws on the faceplate to secure the unit.

Initial Setup:

Connect the PeQ-501a's inputs and outputs from the 500-series chassis to a mixing bus or patch bay using balanced XLR cables. Set the EQ button to the "on" position, and then apply power. For proper performance, balanced TRS cables must be used for all inputs and outputs.

Maintenance Features

The PeQ-501a is designed for reliability with gold-plated PCB internals and all-switched rotary controls, minimizing wear and tear. The unit features a real hardware bypass, which means the signal path is completely disengaged from the active circuitry when the EQ is off, ensuring a clean, unaltered signal.

Safety and Warranty:

The device complies with all applicable RoHS / WEEE European Union directives.
It is covered by a Limited One-Year Warranty against defects in materials and workmanship for the original purchaser.
Servicing should only be performed by qualified personnel.
The manual explicitly states that users should not attempt to service the unit themselves, as this will void the warranty.
The product should not be exposed to dripping or splashing, and no objects filled with liquids should be placed on it.
The unit is not completely disconnected from the AC mains when the power switch is in the OFF position; the mains plug or power inlet serves as the disconnect device and should remain readily operable.