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The Mute Audio GrubDAC

GrubDAC History

In the beginning of September 2009, Erik Soosalu was trying to find a present for a parent's birthday. This same parent had expressed a need for something to deal with the poor quality sound that was coming out of his laptop while watching DVDs during traveling. It just so happened that at the same time, PCBs were available for prototyping the Carrie USB-powered Headphone Amplifier. The Carrie consisted of a PCB which implemented a USB-powered version of amb labs' Mini^3 headphone amp. It was also combined with a BantamDAC as a source, with both PCB's in a single case. This sounded ideal for the present, so Erik prepared work on the parts list and plans to build the Carrie/Bantam. The BantamDAC used a Type B USB connector which was in prevalent use for connecting printers and other devices when the Bantam (and the AlienDAC before it) was first designed. Since then, however, with the advent of USB-enabled cell phones, BlackBerry's, and portable USB disk drives, the mini-USB connector had become popular, especially for portable use. Considering that the parent in question never carried a full-size Type B USB cable with his laptop, the Bantam USB connector presented a problem.

Erik had been working on an implementation of a USB-to-I2S portion of a DAC, based on a previous design. He was also aware that Wolfson Micro had released the WM8524 ground reference DAC chip a couple of months before. These seemed ideal for each other and in a day's worth of work captured the schematic and designed a PCB board that was the same size as the Bantam, but with the different chips and a mini-USB connector. A few minor revisions to the original design, and a prototype board layout was sent out for production. A GrubDAC thread was created on Head-Fi, supporting a close affiliation with Head-Fi user "Joneeboi" and his Carrie design thread. Several users ordered and built the GrubDACs from Erik, with great success.

Carrie USB-powered headphone amp

Carrie with the BantamDAC

Carrie with the GrubDAC prototype
As with any new design and prototype, a few modifications were requested - some needed, some optional. Erik incorporated all of these mods into the final production board design documented herein.

GrubDAC protos with Carrie amps
A while later, Beezar and DIYForums recognized the commonality of the GrubDAC with the Bantam and its potential future use with the Millett MAX V1.2. The new MAX V1.2 PCB can use a Bantam or GrubDAC mounted directly on the MAX PCB. This would be a further application for the GrubDAC, in addition to the Carrie and stand-alone uses. A relationship was worked out with Erik and Mute Audio. The result is the website you see here and the Mute Audio offering now available on

Millett MAX V1.2 with BantamDAC

Throughout its development, the goal was to make the GrubDAC a compatible replacement for the BantamDAC. The BantamDAC is an excellent, versatile small DAC that sets a high bar for features and performance at a low price. The GrubDAC is aimed at that bar, but with a different chipset. We believe the GrubDAC is an excellent alternative to the Bantam and creates a unique opportunity in audio DIY (and one we hope will continue to expand): rolling small, inexpensive DACs with equivalent PCB size, mounting, and connection features!
file last changed:Friday, December 25, 2009 6:00:00 AM
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