Buffalo III “Smart” Stereo Input Configuration
Here is a “smart” input configuration for the Buffalo III DAC, where you can use an interface like the Amanero USB that can pass both I2S and DSD and also connect 3 other SDPIF sources without any external switching device. This configuration leverages the Serial format auto-detect capability of the Sabre32 DAC and its built-in SPDIF MUX. It also requires an external controller such as HIFIDUINO.
In essence, it replicates the input configuration of the Buffalo II DAC and frees up 3 input ports for SPDIF.
BUFFALO II (FACTORY CONFIGURED) INPUT
Notice that in the Buffalo II DAC, Data 3, Data 7 and Data 8 are connected to GND. In contrast, all the input lines are configurable in the Buffalo III DAC. The idea here is to replicate the “D1″ and the “D2″ connections of the Buffalo II DAC and have Data 3, Data 7 and Data 8 available for SPDIF input.
Also notice that the input to the 8 internal DACs are remapped so that only inputs to 4 DACs are required. This remapping is accomplished through the appropriate register (register 14). The integration manual for BIII also specifies input remapping for the “default” stereo configuration.
With this input configuration the DAC automatically switches between a PCM (I2S) stream and a DSD stream. This behavior has been tested with the Amanero board, and it should work with other boards such as the EXA device. [link]
BUFFALO III INPUTS
Here is the input pins for the BIII DAC board (top and bottom).
According to the Buffalo III Integration guide by Leon van Bommel (54 pages worth of excellent documentation). The jumper settings is as such:
The table implies separate input configuration for PCM and DSD. The rest of the guide also instructs the installation and removal of jumpers and dip switch settings depending on the input format (SPDIF, DSD or PCM).
SMART WIRING FOR BIII DAC
Without going further, let me say that this only works for stereo configuration.
By comparing the jumper setting table for BIII with the BII wiring diagram above, we notice that in order to replicate the BII input wiring on the BIII DAC we can do the following:
Use JDSD1 and JDSD2 and then find a way to wire D4 to D2 or to D6. This can be done by using JPCM2 and JPCM3 (and we loose the use of D3). This can also be done by installing an external jumper from D4 to D6 or from D4 to D2. D3, D7 and D8 are made available for SPDIF inputs.
The complete wiring would look like this:
USING HIFIDUINO CONTROLLER
Combining the above configuration with an external controller such as HIFIDUINO, and the appropriate interface (for example Amanero USB) you will be able to enjoy the convenience of switching between PCM, DSD and 3 external SPDIF sources without making any changes in the jumpers or dip switches of the board.
The current version of the code supports does (not yet) have support for actuating the built in SPDIF MUX, but a simple change is described by Mr. Corpius here: [link]
I do not have a BIII, but I have done testing on my BII where I had both SPDIF and I2S signals connected and live at the same time. I was able to switch from I2S to SPDIF by just switching the signal on one pin (D1). You can read more in the Sabre32 tab. Look for “LEVERAGING INTERNAL SOURCE SELECTION”. However, Russ (from TPA) just commented on this post, and expects this configuration to work. You can read his comments in the comments section.
The DSD channels are swapped with respect to the PCM channels [link] and both channel arrangements are “standard”. This means that this “automatic” switching works, but the DSD channels (or PCM channels) need to be swapped. The wiring can obviously be swapped with a relay, but then it is not “automatic” anymore, and you now have a relay in the signal path.
The solution is to swap the DSD channels in the foobar player. I’ve documented the procedure here: [link]
Bunpei recommended this wiring configuration a while back [link]