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Passive parallel mains noise filter for audio and sensitive electronic equipment
What is it?
The AAL Parallel EMI/RFI Filter V2 is a passive mains filter designed to help reduce high-frequency conducted interference present on the AC power line.
Its principle is similar to well-known parallel filters such as the Quiet Line MKIII: it simply plugs into an available mains outlet close to your equipment and operates in parallel across Line and Neutral.
Because the load current does not pass through the filter, it introduces no series current limitation, making it suitable for power amplifiers as well as source equipment.
No active electronics. No Protective Earth connection in the filtering circuit. Just plug it in and leave it connected.
Why did you make it?
I originally developed this filter in 2022 for my own audio applications. The aim was simple: reduce mains-borne EMI/RFI without inserting additional components, connectors or wiring in the equipment's power path.
In 2026, I redesigned it as a fully integrated product while retaining the original filtering principle:
- New custom PCB and updated component selection
- Dedicated insulated enclosure
- Integrated European mains plug
- No intermediate IEC cable or adapter
- Internal access for before/after filter measurements
The result is smaller, cleaner and purpose-built.
What makes it special?
Parallel architecture: the filter does not carry your equipment's supply current and therefore adds no series impedance to its power path.
Multi-cell network: several film and ceramic capacitor values provide filtering over different high-frequency ranges.
Quality components: components are sourced from established manufacturers including TDK/EPCOS, KEMET, Murata, Vishay and Phoenix Contact, with appropriate safety-rated parts and mains transient protection.
Multiple units can be used: parallel filtering is local, so using several filters close to different equipment groups can be beneficial. Discounted pricing is available on request for multiple units.
Measurement capability
V2 includes an internal Phoenix Contact measurement terminal providing access before and after the filtering network. It was designed for the future AAL Noise Meter, currently under development, but can also be used with suitable conducted-noise measurement equipment.
Important: these points are mains-referenced and must never be connected directly to a conventional grounded oscilloscope or analyser. Appropriate isolated measurement equipment and experience with mains voltages are required.
What can — and can't — it do?
This filter is specifically designed for passive parallel attenuation of high-frequency conducted interference.
It is not intended to correct DC offset, ground loops, incorrect mains voltage or faults elsewhere in an audio system.
EMI/RFI conditions vary between installations, so I prefer not to promise subjective improvements that cannot be guaranteed. If you are unsure whether this filter is appropriate for your system, feel free to contact me.
Electrical specifications
- Operating voltage: 230 VAC / 50 Hz
- Connection: Parallel across Line and Neutral
- Protective Earth: Not used by the filtering circuit
- Topology: Passive multi-cell EMI/RFI network
- Surge protection: TDK/EPCOS MOV
- Protection: 2 A time-delay fuse
- Mains connection: Integrated European Type E/F compatible plug
- Current limitation: None — not inserted in series with the load
Why this price?
AAL products are made in small quantities using a custom PCB, dedicated enclosure and components from established manufacturers rather than being mass-produced.
The price includes hand assembly, cleaning, inspection and individual electrical testing while keeping the product reasonably priced and helping finance the development of future AAL projects and measurement tools.
Discounted pricing is available for multiple units.
Who did it?
Designed, hand-assembled and individually tested in France by AAL — Analog Audio Lab.
Practical electronics designed to solve real-world problems.
Early customer feedback
V2 released in August 2026 — customer feedback coming soon.
Links to code and documentation
No additional links provided for this product.
Shipping policy
No information available.
AAL – Parallel EMI/RFI Filter V2
Sold by Analog Audio Lab's store
$66.66
No tax for United States [change]
Stock available: 20
Volume discount | |
2+ items | $63.33 |
3+ items | $59.99 |
4+ items | $53.33 |
The seller
Electronics enthusiast since childhood, musician, and longtime engineer, I design and build electronic devices combining analog audio, embedded systems, and practical everyday innovation.
My background includes:
IT systems & network engineering
analog audio electronics
microcontroller and robotics projects
studio recording and live sound for more than 10 years
Today, through AAL (Analog Audio Lab), I develop DIY and boutique electronic solutions ranging from audio devices and signal conditioning tools to smart everyday electronics designed for reliability, simplicity, and real-world usefulness.
My background includes:
IT systems & network engineering
analog audio electronics
microcontroller and robotics projects
studio recording and live sound for more than 10 years
Today, through AAL (Analog Audio Lab), I develop DIY and boutique electronic solutions ranging from audio devices and signal conditioning tools to smart everyday electronics designed for reliability, simplicity, and real-world usefulness.