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I Put Nam A2-Lite Inside an iRig HD X

17 hours ago
  • An iRig HD X was modified to run the NAM A2-Lite amp model directly inside, eliminating the need for a host computer in the audio path.
  • The interface uses an NXP MIMXRT1011 500 MHz Cortex-M7 processor, which originally only handled audio routing and controls, leaving spare processing power.
  • A2-Lite, a compact recurrent amp model, was fitted into the microcontroller by reconfiguring its memory banks, using 96 KiB DTCM for weights and 32 KiB OCRAM for data.
  • The implementation achieved real-time performance with 16-frame blocks, using under 89% of CPU cycles, despite earlier attempts with DSP-optimized kernels failing the audio deadline.
  • The modified firmware keeps the original codec, wheel volume control, and headphone/amplifier outputs, with USB powering the device.
  • Testing showed numerical equivalence to upstream NAMCore, with a null error of -115.63 dB and correlation of 0.9999999999985, confirming accurate tone reproduction.