I've recently graduated university with an MEng degree in Electrical and Electronic Engineering. As a third year project, I've used an ST-Microelectronics ARM Cortex-M4 based Nucleo microcontroller board as the basis of a programmable guitar pedal.
I would like to begin designing my own pedals as a hobby, starting with digital effects. To do this, I'm putting together my own 'evaluation' board for prototyping with the following core components:
- Anti-aliasing filter
- Re-construction filter
- Peripherals (jack connectors, buttons, toggle switches, I2C display etc.)
I would like to keep my designs professional and relatively low cost (below £100 to prototype).
To produce a device of high quality, I've thought about the following specification:
Sample Rate: 96kHz
This allows maximum frequency of 48kHz to be captured. As the upper limit of human hearing is around 20kHz, this should provide oversampling for greater fidelity.
This also sets the requirements for pre/post filtering, a higher frequency sample rate will also result in simpler filter design.
ADC / DAC Bit depth: 24-bit
Greater bit depth will allow for higher quality (16-bit produces 96dB dynamic range, whereas 24-bit provides 144dB). As there was not much difference in price using an external DAC will increase the dynamic range over the MCU internal DAC / ADC.
Memory requirements 512kB SRAM:
At 96kHz / 24-bit, 1 second of audio requires 96 * 1000 * (24/8) = 288kB therefore 512kB should be suitable, if memory for delay style effects is needed.
As I'm relatively new to this field, I wanted to ask what Microprocessors, ADCs, DACs, Memory would be recommended and does my design approach seem suitable?
So far I've selected the following:
- MCU: DSPIC33FJ32GP202-I/SP
- ADC: NXP UDA1361TS/N1
- DAC: NXP UDA1334ATS/N2
- MEMORY: AS6C4008-55PIN
Any advice appreciated.