Amanero Combo 384 review.
I received the module quickly and in good condition.
I purchased this module because I was looking for a low jitter USB interface that supports PCM up to 384 KHz. I am a MAC user and the Amanero works fine on a MAC without the need for drivers.
Jitter performance is not the best, it gets bad above 96KHz Some suggest to use XMOS-based USB receivers for sample rates above 96 KHz.
The whole point of using isochronous USB audio with asynchronous feedback and two local master clocks is to get low jitter .....
Major reasons for this are poor power supply decoupling, not the best master clocks and a FPGA that injects significant jitter. I2S timing signal from the Atmel processor has lower jitter.
The I2S clock and data signals are not correctly aligned, alignment gets critical at 352.8 KHz and 384 KHz.
The 3V3 regulator is not the best in terms of noise, line & load regulation & PSRR. I replaced it with a pin compatible LP5907-3V3 that offers better performance. Linear Technology has even better one's (LT3045).
I also improved power supply decoupling using chokes (2.2mH) and low esr V-polytan capacitors. Passive filtering of the master clock supply offers biggest improvements in jitter performance.
I replaced the master clocks with lower jitter clocks from Kyocera Electric.
The suggested digital isolators will add 100ps of extra jitter (typical) and input-output coupling capacitance is rather high (4pF).
I am now very pleased with the modified Amanero module.
Only 4 stars because I had to modify the module in order to get desired performance.