I am posting the block level schematics of what you might be looking forward to build a voice recorder.There will be some specs according to which u can choose appropriate component.
I have added DAC and speaker as without play back, recording would not make much sense.
Input amplifier to the ADC can be built using opamp.By observing the output voltage of microphone gain can be selected.
ADC - sampling rate has to be greater than 40 k samples per sec. you can go for 8 - 10 bit ADC's, or else search for microcontroller with the required ADC as a pheripheral on it. This will make things easier. Search in microchip PIc 18F series as PIC gives free samples.
since uC actually has to just read and write from some memory location any microcontroller would do
Memory: If you have time go for compact flash interface. CF+ is a standard.All timing diagrams are available on net. or any other flash or EEPROM option can be considered. keep in mind that read/write cycles for EEPROMs are limited.
or SRAM with seperate battery back up can also be considered as reading and writing then will become simpler.
For power amplifier deisgn such that it drives 8 ohms speaker load. ready power amplifier modules are also available or else push pull amplifier would do.
LM384 is an audio power amplifier.
obiviously DAC output has to be filtered before giving to power amplifier keep that in mind .
The Voice Recorder Reference Design illustrates how to use a C8051F411 for voice application. It is a practical demonstration of C8051F41x high performance analog and CPU throughput capability.
The voice recorder uses DPCM (Differential Pulse Code Modulated) compression to convert 12-bit samples of the ADC and IDAC to 6 bits at an effective sampling rate of 8 kHz. This compression allows for an extended recording time without audibly losing sound quality. Additional ADC features such as Burst Mode and Repeat Count are utilized to improve the quality of the sound samples during the recording process. The C8051F411 Suspend operating mode also allows the voice recorder to reduce power consumption when idle.
This Application Note describes how to record, store and play back sound using any AVR MCU with A/D converter, the AT45DB161 DataFlash memory and a few extra components.
Hello guyz,
i'm new member of this forum...
i'm running projct entitled voice encryption
is there anybody can help me?
do you have any sample of it?
A million thanks in advanced for your help..