High performance active volume control with balanced differential input and ground-sensing output (goodbye cross-channel ground loops!).

It can serve as:

• Part of an integrated amplifier (great with LM3886 or similar chipamp based power stages);
• With an input selector, a high performance balanced line stage or a minimalist analog preamp;
• An output stage for a DAC to form a "digital preamp".

This board uses the WM8816 or MAS6116 for adjusting volume. The WM8816 was a high quality digital volume control from Wolfson (now part of Cirrus Logic). The chip has been used in successful commercial products such as the Marantz SC7S1 and SC7S2 control amplifiers. The MAS6116 is a chip currently manufactured by MAS Oy that is pin- and function-compatible with WM8816.

Also available digitally controlled variants based on MUSES72320 or PGA2310, as well as analog variant with a dual linear potentiometer.

• Bare board only.
• Parts are not included and need to be obtained separately.
• Assembly is required.

Features and benefits:

• Balanced differential input with excellent common mode rejection - works very well with single ended sources, too!
• Output stage that can be configured as balanced - best for downstream stages with differential input - or ground sensing (a.k.a. ground cancelling) - best if followed by a single-ended input referenced to its local ground, such as the vast majority of audio power amps;
• Compact (2.9x2.6in or 74x66mm) two layer PCB, all easy to solder though hole parts except for the WM8816/MAS6116, which only comes in a surface-monunt package.

The WM8816/MAS6116 is controlled via its SPI interface and requires a microcontroller. You can use anything suitable, such as a 5-volt Arduino. To help you get started, we provide a simple Arduino sketch.

Documents:

• Schematic
• Board size and component placement
• Part list (BOM)
• Shared project at Mouser (includes all parts except WM8816)
• Example Arduino sketch
• WM8816 datasheet
• MAS6116 datasheet
• Discussion at diyAudio.com

Note: WM8816 is obsolete, however MAS6116 is available from e.g. Profusion.