The new DAC MK 5 that I’ve been working on for Audio by Van Alstine has finally been released.
I am very grateful to Frank Van Alstine for giving me so much room to develop the best reasonably priced DAC I know how to design. The results have so far exceeded everyones expectations, including my own. We all learned a lot through the process of designing this unit, which is as it should be. Rapid prototyping turned out to be instrumental in exploring a number of early electronic design alternatives. Looking forward to the reviews!
Audio by Van Alstine has adopted my discrete Class A audio module into two of their products. The Vision DAC uses the module in its differential anti-imaging filter and output stage and the Vision SL Preamp uses it for line stage amplification. The pair will be premiered at the Axpona Audio Expo in Chicago this weekend. Looking forward to feedback from the show.
As part of my Open source audio remote control initiative, I’ve just published Volume-AlpsRK16814MG, an open source hardware design that integrates a high-quality Alps motorized quad potentiometer with an H bridge. The design lets you control the motor’s direction using two logic-level signals: VOL_UP and VOL_DOWN. The fact that it’s a quad pot means you can use it to control regular stereo volume by ignoring one of the dual gangs or a differential stereo signal.
Here’s the schematic* to give you an idea what it’s doing. Gerbers and PCBs are available at OSH Park.
I’ve also modified the remote control receiver to better support motorized pots. There is now a compile-time option that lets you latch and unlatch the VOL_UP and VOL_DOWN signals rather than produce repeated VOL_UP and VOL_DOWN pulses—which makes control of motorized pots more fluid.
I’ve started a FLOSS remote control receiver project for DIY audio preamplifiers. I think it’s just about good enough to make public.
Remote control is one of the more challenging things for an audio DIY person to implement, so I thought having an open source hardware and software platform for doing this would be useful. It uses our good friend Arduino for brains and works with the Philips RC-5 protocol. I like RC-5 because its the closest thing I know of to a universal, well-documented, brand- and model-agnostic protocol.
The IR command decoding is done using Guy Carpenter’s excellent RC5 library. I also considered using Ken Shirriff’s multi-protocol IR library. Ken’s library works with a large number of protocols, but I thought its larger memory footprint might preclude porting this thing to tiny AVRs.
Here’s a workaround I used in a KiCad layout that involved a DRC error with a module’s (non-conducting) mounting pin. The mounting pin is physically close enough to an electrical pin that it makes the DRC clearance test fail. The proximity isn’t actually a problem because the offending pin is just so much mounting foo for the part, but KiCad doesn’t know the difference.
The workaround is to edit the pad for the mounting pin and assign it the same pad number as the pad the DRC thinks it’s too close to. (See the two pads numbered 3 in the above image). Kludgey, but it silences the (not really an) error. I made this change in the PCB layout rather than in the library module as it won’t be a problem on boards with smaller copper clearance.
Pictured here is a prototype of a miniaturized version of the audio module I’ve been working with for the last few months. A high-end audio manufacturer is currently evaluating the module for use in a new line of products. More as it develops.