Imroved Soft Start + DC Blocker aka iSSDCB

The original Soft Start + DC Blocker published on this website a few years ago required quite complex wiring encompassing both the mains supply to the transformer and wiring from the rectified and DC-smoothed secondary.  Additionally, the mains power switch had to be rated for the full primary AC load current which placed severe limitations on builders looking to find an attractive switch that looked good on a power amplifier front panel. These issues, rightly, put many constructors off and they looked elsewhere to solve their power ON/OFF,  in-rush current, and mains DC offset problems.

Offering a neat, easy-to-assemble solution, the new Hifisonix Improved Soft Start + DC Blocker + Power On/Off Controller  aka iSSDCB overcomes all of those problems:-

1. Greatly simplified wiring required only on the mains supply side of the transformer
2. Double the full AC mains load capability of the original SSDCB – 4.6A vs. 2.3A
3. Allows use of attractive anti-vandal power control switches – max required switch current rating is 30mA DC – for full ON/OFF power control
4. Very low standby power draw of c. 0.2W
5. In-rush current limiting of 10A for 2-3 seconds
6. Small compact, easy-to-assemble PCB

Here is a presentation describing the circuit, assembly, test, and wiring details  Improved DC Blocker Soft Start

Here is the BOM, Updated on 4th February 2024 (thank you Luigi from Italy for the feedback) iSSDCB BOM Feb 2024

Head over to the shop to buy a PCB!

As always, if you have any questions, please feel free to contact me on Hifisonix!