Another USB Interface for DIY
The company is called “Amanero Technologies” located in Pisa, Italy.
I am excited about this device because, well, it is cheap!. Technology is always changing. For the audio hobbyist, there is no such thing as the “ultimate device” or “last upgrade”. Therefore buying cheap but well designed products is the best approach because soon enough you will replace it with something better. As the subtitle of this blog says, “Lot of Value, Little Money”
The design is similar to other USB to I2S interfaces such as HiFace, XMOS, ExaDevices, etc, but it is priced substantially lower without sacrificing any of the essential desirable features (and also without adding extra features). For example, it does not use any kind of signal isolators as they may only benefit certain noisy environments but always introduce jitter. I like the minimalist, low power, low noise and low jitter approach.
Data Sheet: [link]
- Clean, very minimalistic design with no other feature than an I2S output and ready to be “plugged” into any DAC.
- The local regulators are the now-popular ultra low noise ADP-150 and ADP-151 from Analog Devices.
- The clock is taken from the two external local oscillators (and not generated by the FPGA) therefore keeping added jitter to the absolute minimum.
- The external oscillators are powered by the ADP-151 regulators through an LC filter which further decreases power noise (not an exotic implementation, but good practice).
- Supports up to 384 kHz and 352.8 kHz sample rates.
- Supports DSD
- Schematic for the USB interface (the Atmel chip): [link]
- Schematic for the data clocker (the Xilinx chip): [link]
- This is important for us diyers that can’t leave any design alone!
- Self powered (USB VBUS). USB power goes through a π filter (CLC) before the local regulator. The second regulator (another ultra-low noise ADP device) takes its input from the first LDO. This results in even cleaner power to the CPLD, the data clocking device
- In the output connector you have 3.3V from the LDO. For example you can use this pin to know when the cable is plugged.
- If you don’t like the USB VBUS supply, you can remove the LDO and power the module directly from the 3.3V pin present in the output connector.
- Power consumption is about 600 mW at maximum speed
OTHER NOTABLE FEATURES
- Supports MAC OS, Linux and Windows
- Single: US$97
- 60+ units: US$49
The USB interface is an Atmel microprocessor (SAM3u1C). The choice of using a general purpose microprocessor as the usb interface makes this device different from all other interfaces which implement a specialized usb interface chip. I don’t know the reason, but perhaps this makes it much easier for upgrading the firmware of the microprocessor itself and also for updating the firmware of the Xilinx CPLD.
On a side note, the SAM3U microprocessor will also be used in the upcoming Arduino DUE
The data clocking device is a Xilinx CPLD (XC264A). A CPLD is like an FPGA but lower complexity and lower power. Another guess: the designers choose the smallest device necessary just to do the I2S data and DSD clocking. No extra features like clocking a SPDIF stream.
Two low jitter clocks for deriving the master clock for the different sample rates
(Manufacturer’s data from post 78 at diyaudio)
-78dBc @10 Hz,
Using a jitter calculator we get the following value:
Not bad. The crystek CCHD-950 80MHz originally used in the BII measured at 2.286 psec [link]
Pin description [post 238]
- DSDOE: = 1 when a DSD stream is incoming.
- MUTE: has been assigned to PIN 11 and is asserted to 1 when a sample rate change is incoming or when there is a stream format change DSD / I2S. You can use this pin to avoid noise when the dsd is detected.
- Pin 6 is the Master Clock MCLK 22,5792Mhz or 24.576Mhz. (I think this is pin 5 FSCLK)
- TWC.D is an I2C bus, I m preparing a ConfigTool that let’s the user configure Events in the module. For example you can assign I2C address and values to put in the I2C bus when the volume is changing or when a sample rate is changing.
There are a couple of fuzzy videos on youtube where you can get a glimpse at the driver user interface.
AUDIOPHILLEO ALSO USES A MICROPROCESSOR…
The Audiophilleo USB interface chip is also implemented in a general purpose microprocessor. According to 6moons,
(The Audiophilleo uses) an ARM9 microprocessor… The processing power is considerable and allows the Audiophilleo to provide advanced dithered digital attenuation, ramped muting, balance and polarity reversal on the fly. New firmware containing the code for all these functions can be downloaded in a few moments which in turn enables easy field upgrades. The resulting processed data are passed to the output stage through miniature galvanic isolators that are much faster than the usual optical types. A TDK Lambda regenerative power supply separates the rails and grounds of the two subsystems. So now we’ve got clean power and data neither of which is contaminated by dirty power or clocks.
… The “non-minimalist” design approach.
On paper (since I don’t have one yet ), this device seems like a winner; and considering the price, it should be at the top of the list. For the next level of improvements, you will have to look at something like Ian’s FIFO device. The only “unknown” at this point is how well has the USB h/w and s/w been implemented.
HOW ABOUT MUSILAND?
Readers know that I have been a long time fan of Musiland Devices. They are very affordable, have good drivers, and are fairly easy to mod. For the diyer, this device addresses the two things I wished Musiland had improve, namely lower noise regulators and clocks from external oscillators (rather than generated in the FPGA). Feature-wise though, the Musiland devices still pack a lot of things for the money: more interfaces, built-in DAC, built-in headphone Amp, user-interface with lost of controls, etc. For an all-in-one USB solution, the Musiland devices are still on the top of my list.
You can join the discussion at diyaudio.