AVA DAC MK 5 released

DAC MK 5 with Berkeley
Berkeley investigates the new DAC MK 5

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!

Acrobotic’s ESP8266 Tips & Tricks

NodeMCU devkit

There’s a growing series of good videos covering ESP8266 Tips & Tricks on ACROBOTIC’s YouTube channel. The ESP8266 has become quite a darling in the IoT world, and a seriously cool community is growing around it.

NodeMCU devkit picture by Vowstar (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.

More KiCad modules


I’ve added a bunch of modules to my KiCad library. These have not yet been vetted, so approach with caution. Here’s what’s new or changed:

  • New library mfk-ipc-7351-diode.mod with:
    • mfk-SOD3716X135N (SOD-123 diode)
  • New library mfk-smd-not-ipc.mod with:
    • mfk-fairchild-SOT23 (Fairchild version of SOT-23)
    • mfk-fairchild-SOT23_213 (as above but with “BEC” pinout)
    • mfk-fairchild-SOT233 (Fairchild version of SOT-233)
    • mfk-fairchild-SOT23_2313 (as above but with “BCEC” pinout)
  • Changes to mfk-ipc-7351-transistor.mod:
    • Deleted mfk-IPC7351-trans-SOT65P210X110-6N_10mil
    • Changed silk width in mfk-SOT65P210X110-6N (SOT363) to 10 mil.
  • New part in mfk-vishay.mod:
    • mfk-Vishay-TSOP341xx-alt (alt version of mfk-Vishay-TSOP341xx)
  • New part in mfk-keystone.mod:
    • Added mfk-KEYSTONE-621

AVA adopts my audio module in new DAC and preamp designs


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.

Motorized potentiometer for FLOSS remote control


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.

*Subject to change!

Open source audio remote control


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.

Details on the project are available in my RC5-Preamp GitHub or GitLab repository.

KiCad workaround for mounting hole too close to pad


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.

BTW, the module is for a Keystone 970 RCA jack and is available in my Bitbucket repo.