What is it?

The AAL – Audio DC-Blocker is a passive mains DC filter designed to reduce transformer hum, mechanical vibration and buzzing caused by DC offset on the AC mains.

Especially effective with toroidal transformers commonly found in audio amplifiers, DAC power supplies and Hi-Fi equipment.

Designed with carefully selected and optimized components, the circuit operates transparently without affecting dynamics, transient response or audio quality.

Typical symptoms solved

• Transformer buzzing or humming noise
• Mechanical vibration from toroidal transformers
• Transformer hum or buzz appearing mostly in the evening or at certain times of day
• Equipment becoming quieter when connected to a different outlet or circuit

Why did you make it?

Many modern electrical appliances inject asymmetrical loads into the mains, creating a small DC component that can saturate transformer cores and cause audible buzzing or vibration.

The AAL – Audio DC-Blocker was designed to help restore quieter operation and improve listening comfort while preserving musicality and amplifier dynamics.

Typical Applications

• Power amplifiers with toroidal transformers
• Integrated amplifiers
• DAC power supplies
• Tube equipment
• Hi-Fi systems
• Studio equipment with noisy transformers

Particularly useful when:

• Transformer hum increases in the evening
• Equipment becomes quieter on another outlet or electrical circuit
• Toroidal transformers mechanically vibrate or buzz

What makes it special?

Optimized for your equipment

Fuse value and optional inrush-current limiting (NTC) are individually selected according to the connected equipment.

This helps ensure optimal protection and proper startup behavior..

Example:

230V / 2.3A device → fuse and NTC selected accordingly.

If unsure, simply provide your equipment power rating or rear-panel specifications.

Carefully selected components

• Audio-conscious component selection
• High-quality safety capacitors and power components
• Robust thermal and electrical margins
• Designed for reliable operation without compromising audio performance

Electrical specifications

• 230V / 50Hz operation
• Nominal current: 4.35A
• Suitable for equipment up to approximately 1000 VA (depending on transformer type and startup behavior)

Why this price?

Built using carefully selected high-quality components (Cornell Dubilier, WIMA, Wishay, TDK.) chosen for performance, reliability and long-term durability.

All parts are sourced from reputable suppliers to ensure quality and traceability.

Who did it?

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

Practical electronics designed to solve real-world problems.

analog.audio.lab@gmail.com

Early customer feedback

• “The transformer noise completely disappeared.”
• “Everything works perfectly — I’m delighted.”
• “A real improvement in listening comfort.”
• “Even the transformer mechanical hum is gone.”
• "..."