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FlexFX USB/DSP Audio Board
FlexFX USB/DSP Audio Board
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Old 15th September 2018, 01:32 AM   #1
markseel is offline markseel  United States
diyAudio Member
Join Date: Nov 2017
Default FlexFX USB/DSP Audio Board

Here's a 1.0" x 1.4" XMOS board with a XUF216 on it.

FlexFX™ - Programmable Digital Audio Effects Platform by Mark Seel —Kickstarter

GitHub - flexfx/flexfx.github.io: FlexFX Audio/DSP Firmware Development Kit

Contains the CPU, oscillator, 1.0V regulator, 3.3V regulator, reset supervisor, and USB connector.

Can be self powered or bus powered. The XTAG/JTAG signals are exposed in case you want to program your own custom firmware for it. Otherwise you can use the free FlexFX dev kit on GitHub to create custom audio effect applications and use the USB for firmware downloading.

Has pins for ground, V5, Vbus, five 1-bit ports on tile 0, two 4-bit ports on tile 0. Tile 1 is dedicated to DSP.

A guitar interface board has also been designed (see KickStarter). A headphone amp board and a 8-channel balanced out interface board are also in the works.
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Old 16th September 2018, 05:30 PM   #2
markseel is offline markseel  United States
diyAudio Member
Join Date: Nov 2017
I'm making a small board that stacks directly on top of below the USB/DSP module. It's a headphone amp. The ADC is a AK4822 - not the best but not too bad, and does have fully differential outputs. Each of the four outputs (two per channel) drive low-noise unity-gain buffers that drives it's own RLC 2nd order low-pass to remove noise from the sigma-delta converters. This filters have a flat response out to 200 kHz, a stop band of -60dB at 6.144 MHz (frequency of the sigma-delta's), and less than 4 degrees of phase shift at 20 kHz. The four buffers/filters drive two Analog Devices AD8397 high-current dual OPA's. Each AD8397 forms the output drive and the ultra-low impedance virtual ground. Each L/R channel has it's own dual AD8397. Simulations show this output circuitry driving a 32 ohm inductive/capacitive/resistive load (model of a headphone driver) to have distortion well below 0.00003% at 1 Vrms (2.818 Vp-p) and a noise floor of -117dB, both with a 1 kHz 0 dBfs signal - not sure if I trust these Spice results or not but so far so good!. The board is only 1.0" x 1.5".
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Old 19th December 2018, 04:21 AM   #3
jawnypants is offline jawnypants
diyAudio Member
Join Date: Dec 2018
Mark, sorry to see the kickstarter campaign didn't make it,.. yet! I'm curious if you are producing the USB module at this point. I have a few small scale project products in mind that could work (I think) nicely off the basic module you've created. I'm super impressed! Let me know. Thanks,
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