RelaiXedPassive -- audio attenuator


The RelaixedPassive is the 3rd member of my RelaiXed designs. It is an audio volume control and input channel selector with a minimalistic passive design: there are are no active parts in the audio path: no transistors, opamps, tubes. It is a true attenuator. This attenuator design inherits several aspects of my earlier RelaiXed preamplifier designs:

The avoidance of clicks is the major improvement with respect to my original attenuator design of several years back. The main difference with the RelaiXed preamp is of course its passive nature, and the use of standard (single-ended, cinch connected) audio as opposed to a balanced (XLR) design.

This attenuator specifically targets integration in the same cabinet with some power amplifier of your own choice. Integration with a power amplifier avoids longer cinch cables and connectors at the output of the attenuator. Due to the relatively high output resistance of a passive volume control, passive attenuators in general are sensitive to cable quality and cable type. Integration with the power amplifier removes this sensitivity.

To take further benefit from the IR remote control in the amplifier integration, this design comes with a full-fledged power switch control with soft-start functionality. Through a heavy power relay and strong power resistors, the soft-start mode supports the safe switching of large toroid transformers and/or large capacitor banks in your power supply. On-board fuses for the control and the mains power output and the little on-board transformer simplify the wiring in your amplifier chassis.

Design information

Component availability

The PCBs for this version are not available anymore. Please check out the current revision.

Further design options

Probably most of this text should better move into a real user guide, but for now:

Thanks for your interest,
Jos van Eijndhoven

Please note that these audio developments are just hobby for me, next to very busy job. These web pages result in many emails to me, which I cannot always answer quickly. So, please, have some patience with me. I always try to answer within a week...
November 15, 2014