What is it?

The AAL – Subtle EQ is a fully analog audio equalizer designed for simple, intuitive and musical tone shaping.

Available in RCA (unbalanced) and XLR (balanced) versions, it offers three broad tone controls — Treble, Mid and Bass — allowing you to gently shape the sound without the complexity of a conventional parametric equalizer.

Three selectable gain modes are available:

• Gentle – Lowest gain setting for subtle adjustments.
• Subtle – Intermediate gain setting.
• Enhanced – Higher gain setting.

These modes adjust the overall gain of the processed signal, without changing the depth of the EQ curves.

A relay-operated True Bypass allows instant comparison between the processed and original signal.

Stereo / Dual Mono operation

Both versions offer two operating configurations:

Stereo / Linked

Three stereo potentiometers control Treble, Mid and Bass simultaneously on both channels.

Ideal for Hi-Fi systems, stereo sources and mix buses.

Dual Mono

Each channel has its own independent Treble, Mid and Bass controls (six potentiometers in total).

Ideal for independently shaping two audio sources, such as vocals and guitar, two microphones or two instruments.

Two versions available

RCA Version

Designed for unbalanced line-level connections commonly found in Hi-Fi systems, DACs, preamplifiers and other audio equipment.

XLR Version

Designed for balanced line-level connections, making it particularly suitable for studio equipment, audio interfaces, mixers and professional audio setups.

Both versions share the same musical philosophy and analog tone-shaping approach.

Why did you make it?

Sometimes an audio system sounds technically good but just a little too... polite.

I wanted an equalizer that could add presence, body and enjoyment without turning listening into an exercise involving dozens of controls, frequency displays and complicated settings.

The project started by experimenting with a simple existing analog tone-control concept.

I liked its philosophy, but wanted to see how far it could be taken with completely redesigned PCBs, carefully selected components, a regulated symmetrical power supply, improved grounding and decoupling, relay True Bypass and extensive testing.

Several prototypes, many measurements, circuit modifications and countless listening sessions later, the AAL Subtle EQ was born.

The idea remains deliberately simple:

Three tone controls. Three gain settings. Adjust by ear and enjoy the music.

What makes it special?

The Subtle EQ is not intended to replace a surgical or corrective equalizer.

It is a broad, intuitive analog tone-shaping tool, designed to make musical adjustments quickly and naturally.

Its deliberately simple interface hides carefully developed electronics:

• Completely redesigned AAL PCBs
• NE5532 low-noise audio operational amplifiers
• Panasonic, Vishay, WIMA, KEMET, AVX and other quality capacitors
• C0G/NP0 ceramic and film capacitors in the audio networks
• 1% metal-film resistors
• 0.1% resistors in critical positions
• Relay-operated True Bypass
• Stereo / Linked and Dual Mono operation
• Optimized PCB routing, grounding and power-supply decoupling
• Components sourced from authorized distributors such as Mouser and TME

The XLR version additionally includes dedicated balanced input and output stages.

The electronics have been developed through extensive measurements and real-world listening tests rather than simply reproducing the original circuit.

A new handmade enclosure

The enclosure has also evolved.

The Subtle EQ now features an improved 3D-printed enclosure assembled from separate parts, designed and manufactured in-house.

This construction provides a cleaner appearance while keeping the device accessible, serviceable and economical to produce.

Minor cosmetic marks inherent to 3D printing may still be present. They do not affect the operation of the device.

Each unit is hand assembled, inspected and individually tested before shipping.

Electrical specifications

Common specifications

• Audio topology: Fully analog, two-channel
• Operation: Stereo / Linked or Dual Mono
• Tone controls: Treble / Mid / Bass
• Gain modes: Gentle / Subtle / Enhanced
• Bypass: Relay-operated True Bypass
• Internal audio supply: Regulated symmetrical ±15 V DC
• External power supply: 24 V DC adapter included
• Signal type: Analog line level
• Enclosure: In-house 3D-printed construction
• Assembly: Hand assembled and individually tested

RCA version

• Inputs: 2 × RCA (Left / Right)
• Outputs: 2 × RCA (Left / Right)
• Signal format: Unbalanced
• Operational amplifiers: 2 × NE5532

XLR version

• Inputs: 2 × balanced XLR (Left / Right)
• Outputs: 2 × balanced XLR (Left / Right)
• Signal format: Balanced
• Operational amplifiers: 5 × NE5532
• Measured 24 V input current: Approximately 102 mA
• Measured 24 V input power: Approximately 2.45 W

Both versions use an entirely analog signal path, with no DSP or digital audio processing.

Why this price?

The Subtle EQ began with a simple and inexpensive circuit concept, but the final AAL version is very different from the low-cost modules that inspired the project.

The price reflects:

• Custom-designed and manufactured PCBs
• Carefully selected branded components
• Components purchased through authorized distributors
• Dedicated regulated symmetrical power supply
• Relay True Bypass
• Additional balanced circuitry in the XLR version
• Several prototypes and design iterations
• Many hours of measurements, listening tests and development
• Manual assembly, soldering and wiring
• Individual inspection and testing

The enclosure is designed and 3D printed in-house, helping to keep manufacturing costs reasonable while prioritizing the electronics and audio performance.

My goal is not mass production, but to offer carefully built analog audio equipment at a fair and accessible price, while supporting the development of future AAL projects.

Early studio feedback

An early XLR prototype has been tested by a sound engineer in real studio conditions, including mixing, vocals and guitar recordings.

The first impressions were particularly encouraging:

"The highs are really smooth and pleasant, and so are the other bands. Considering how simple it is, I really think there's something here. My first impression was: wow!"

After further testing on a mix bus, the engineer also appreciated how quickly the EQ could achieve a pleasing musical result.

The broad tone controls were particularly appreciated for their ability to shape the sound without suddenly emphasizing unpleasant frequencies.

This feedback supports the original philosophy of the Subtle EQ: simple controls, broad corrections and musical results.

Who did it?

Designed, hand-assembled and individually tested in France by AAL — Analog Audio Lab.

AAL is a small independent electronics workshop focused on practical analog audio devices, carefully selected components, serviceable designs and small-scale handcrafted production.

One designer. One workshop.

Practical analog electronics designed to solve real-world problems.