Twisted Pear Buffalo III DUAL MONO DAC Build

Old news, when I built my Twisted Pear dual mono Buffalo III DAC I wanted multiple inputs. I wanted the ability to play SPDIF, I2S and DSD via USB and I2S/DSD (CD/SACD) from my modded Denon 3910. No problem.

But I got a big surprise along with some other dual mono builders who wanted to play DSD. When you have a DAC board for each channel and wire it as directed, DSD or SACD plays in mono due to a mapping issue inside the DAC boards. However a single Buffalo III DAC plays I2S and DSD/SACD in stereo when wired as directed. I could wire my dual mono to play DSD in stereo but then standard PCM would not play via SPDIF or I2S input. In other words, one or the other via wiring inputs on a dual mono build.

With no firmware type fix it requires some digital switching. Russ at Twisted Pear came up with a solution using their OTTO II digital switch, but that fix would not work in my configuration. I could live without SPDIF inputs and stick with USB to I2S/DSD, but didn’t want to give up my Denon 3910 input.

My long delayed fix uses a couple of sealed signal switching relays installed between the Sidecar switching board and the Right and Left channel DAC boards. A standard relay transistor/diode flyback circuit was used to actuate the relays. It offers folks a second working option for a similar configuration.

Basically I open one circuit to each DAC board and connect it to the other circuit. For DSD, Left channel board, D2 circuit needs to be opened and connect to D1. Right channel DAC board, D1 needs to be opened and connected to D2. With relays unpowered, I can play I2S in stereo, with relays powered, DSD will play in stereo. Hardest part is carefully cutting the ribbon cable apart and snipping/stripping ends. Solder them to the correct relay posts and life is good. For now I flip a toggle switch to select DSD. Over the winter I may look into re-writing code so it’s all automatic when selecting sources.

Main thing is it works great! No noise added, no SQ loss.

headrott wrote: »

Congratulations Rich on figuring out a fix for this troublesome issue. I know others will benefit from it as well. I do not have a dual mono configuration myself, but I know some others on the TP forum do. Great and important fix!

FTGV wrote: »

Nice fix Rich.Now the next step is to configure that dac for multi ch DSD downloads that will become all the rage.:eek::cheesygrin:

Well it is an 8 channel DAC….but two channels in two channel is plenty for me.:biggrin:

Thanks for the kind words. Russ isn’t too excited about my fix. He says it isn’t really a fix because nothing was broken.:rolleyes: And now the playing DSD in mono in a dual mono config is just the way the ESS chip is designed to operate. Had I known that early on, and I did have a build thread started over there at TP that included the Denon 3910 to export DSD, I could have made the major changes in placement to accommodate his fix. Oh wait, nothing was broken so it’s not a fix…it’s a get DSD to play in stereo in dual mono confg thing.

His way requires Bit Clock to be run direct to DAC boards due to only four circuits on the OTTO II. That causes issues if you use their Sidecar as it has four "side" inputs, one being Bit Clock. So you'd have to remember to use the Bit Clock output pin on the Sidecar as a data circuit when connecting to DAC boards. If you have SPDIF on the other side of Sidecar, what do you do with that now?

I see questions about multichannel DAC's every now and then so folks are still building them.

I guess I can see his point about the semantics. A junkie needs his fix, I need my DSD to play in stero fix. Maybe dual mono DSD stereo solution? Nah, it's a fix.

The mapping thing...images thanks to HifiDuino. One thing I haven't done after the relay fix is try the quantizer settings. That changes how the 8 dacs are combined. My previous just play DSD harness fix just opened the opposite channel circuit per side, that is open right to left channel DAC, open left to right channel DAC. D1 is the key, it's word clock with PCM, Left channel with DSD. I even tried some register 14 remapping in code before this fix.

Due to using the Sidecar and serial control of DAC, I use no DSD jumpers on board as illustrated. I am the DAC's total boss, do dis, do dat....lol