DC Blocker Trap Filter – Assembled and tested PCB – v.3

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Fully assembled and tested DC Blocker/Filter/Trap PCB – v.3


Nowadays the AC mains network is heavily polluted by various domestic appliances, industrial electrical consumers etc. This can lead to buzzy toroidal transformers (especially the power ones). Proposed DC trap (blocker, filter) will remove or at least lower the buzzing.
Schematic is similar to this one used in well known Vladimir Shushurin’s Lamm-1 amplifier. An article with in-dept explanation of how DC blockers work can be found on Rod Elliot’s site (

Here is offered fully populated and tested DC Blocker PCB which is ready for plugging into your system. It is a successor of the very successful second version of the board.

It retains some of the  previous board specifications:

Dimensions of PCB: 88×94 mm.
PCB type: FR4 1.6 mm. Copper thickness: 70 um (2oz). Surface finish – Nickel Gold (ENIG).
TWO-layer design which allows the current handling capabilities of the board to be doubled.
All current conducting traces are widened as much as possible which additional raise the max. handled current.

PCB has solder mask coating on top and bottom layer for best durability.
Silk screen with parts layout is placed on the top of the PCB.

In the current 3-rd PCB version is incorporated the ability for mounting of 6 high-power discrete diodes which rises the DC blocking voltage up to 2V.

The possible usage of protective diodes (which number defines the DC blocking voltage) is given on schematic below:


DC Blocker is built with following parts:
– two MASSIVE 47 000 uF EPCOS capacitors (the bigger is capacitance, the higher are handled currents)
– one high-current Rectifier Block or 6 high-current discrete diodes 10A4
– one 10W power resistor
– one WIMA MKS4 400VAC capacitor
– two MOLEX 3-terminal connectors for AC input/output
– one PCB for DC Blocker.

All parts used are freshly obtained from reliable sources (Mouser, Farnell, Digi-Key etc.).

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Fully assembled and tested DC Blocker/Filter/Trap PCB - v.3
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Additional information

Weight 0.25 kg
DC Blocking Voltage

1.4V (Bridge rectifier), 2V ( Six discrete diodes)