Not sure the KickStarter is going to make it - doesn't seem to be enough interest

But anyway here's the collection of PCB designs related to FlexFX. These analog boards can be stacked above or below the USB/DSP board. Not sure where this is all going but I'll build the analog boards to test and then release the Gerbers.
From left to right ...
1) The FlexFX USB/DSP board.
2) Guitar interface using AK4621 differential in/out stereo CODEC. Should be a very quiet interface.
3) 8x8 analog interface using four AK4556 24-bit CODECs. 4 layer board packed really tight. So given layout compromises it will have modest performance compared to the AK4621 guitar interface. But with 8 ins and 8 outs all with DC coupling (CODECs are configured to disable the HPF so that low frequency or DC signals can be sensed) this could be used for synth projects or effects where you want the parameter controls to used in real time.
4) Headphone amplifier with all DC coupling (AK4482 DAC outputs to headphone jack). Four low noise buffers (two per differential DAC output) driving 2nd order RLC low pass filters (to filter out DAC sigma-delta conversion noise) and two dual high current OPA's (one AD8397 per channel for virtual ground, DC shift, and headphone driver). SPICE shows 1dB flatness out to 170kHz, less then 6 degrees or phase shift at 20kHz, -70dB attenuation at 6.144 Mhz (frequency of sigma-delta), ~0.0003% THD at 10kHz, ~0.00003 at 1kHz, while driving a 32 ohm simulated headphone load at 1 Vrms (2.8 volts pk-pk).
