I had been toying around for years on building an all-in-one streamer, DAC and headphone amp. I had a few goals in mind and adjusted my components based on what was available at the time and cramming it into a 12x12 chassis.
• USB and Ethernet inputs
• Phono output
• Headphone output via headphone amp.
• Synchronous re-clocking of both USB and Ethernet based signals.
• Beaglebone Black SBC or similar.
• Decent quality DAC capable of at least 24/192.
• Ability to bypass headphone amp to hook up to another amp.
Since I decided to base my project around the BBB I only had a few options for what music player to use. I wanted to go for the most simple (not too much linux) but fully featured option. I decided to go with Volumio. There is a specific build for the Beaglebone Black that allows for external clocking to the BBB.
At the time of the project’s origins, around 2014, people in the diyaudio.com community were playing around with re-clocking with ESS Sabre DACs. After some experimentation, Acko, a DAC designer from Australia, came up with a board that allowed for high quality low jitter clocks along with super fast flip-flop chips from Potato Semi. Now I had to find a decent DAC to go along my re-clocking board. In that same time frame I had just finished another USB DAC based on the ESS ES9023 that contains a really nice filter buffer on its output stage. Since I had an extra filter board I just needed to get the DAC to match. I went with the Acko DAC AKD23P.
The next step was to find a suitable headphone amp. Like the ES9023 based DAC, I had also built a really nice super low harmonic distortion amp called the The Wire (by OPC on diyaudio). The amp is smaller than a credit card. So perfect for a headphone amp in my AIO unit. The bonus is the power supply for the amp also powers the output stage of the DAC. Both need ±15V.
Now that I had a DAC, headphone amp, and re-clocking unit I just needed to solve how I was going to get the two sources - Amanero USB transport and Beaglebone Black into the chain feeding my re-clocker. After some digging, I found a product from Twisted Pear Audio called the OTTO II. This unit is a i2s switch. It can take two inputs and go to one output.
After solving most of the puzzle, I had a few more components to come up with - power supplies for the Beaglebone Black and the DAC. Both required 5v supplies, but I didn’t want to have just one because it would break the galvanic isolation provided by the re-clocking unit. I needed at least 800mA for the Beaglebone Black so I went with a low noise 5v supply from DIYINHK. For the DAC, I went with a supply meant for digital applications that was getting a lot of hype on diyaudio - the Reflektor-D designed by Salas.
Let’s put it together! …Not so fast. Not sure why but it took me 6 years to complete the project. Life happens. You’re happy with your current gear. Other hobbies pop up. You get the idea. Either way, it’s mid to late 2019 and I’m itching to finally get it done. I just needed a few more things - wire it up, a chassis, etc. Chassis are expensive, especially to have someone do the milling and drilling work for you. I was tired of paying $200+ for the chassis alone. So I got myself a drill press, bought a chassis from Par-Metal and went to town. I wired things up and NADA! No sound at all. I had to work my way back down the chain to toubleshoot… In the end I had 3 major issues… re-clocker wasn’t passing on SDATA, USB would play anything, and mains power switch wouldn’t turn on BBB. Eventually, with some trial and error I solved all three issues - more solder on a chip, a different firmware on the USB board, and an in-line switch between BBB power supply and BBB - strange?!?
So now we’re done! How she sound! Freakin’ awesome! Here are some pics…