HT8950A Voice Modulator (Sound Effects – Funny Sound)


Voice Modulator project is designed around HT8950A to provide two special sound effects viz.


This project  provides two special effects: vibrato and robot. The vibrato effect is generated by alternating the frequency of an input signal up and down at a rate of 8Hz. The robot function, on the other hand, converts an input voice into a robot voice. Both effects can be selected depending on which pin is triggered, either ROB or VIB. For the output frequency level shifting, the chips provide seven steps which can be selected from the two groups of pins namely, SW0, SW1 and SW2 for electronic direct selection and ROB, TGD, TGU and VIB for push button selection.

The HT8950 include a built-in microphone amplifier with an internal bias, an 8-bit A/D converter, a built-in SRAM as well as a current output type 8-bit D/A converter. The 8-bit A/D and D/A converters with a sampling rate of 8kHz ensures a high quality and high S/N ratio output voice. The chips provide an LED indicator which flashes in accordance with the volume of the input voices.


Input – 6 VDC @ 300 mA
Output – Speaker, 8 ? / 0.5 W
7 Step level shifting (Volume Control) SW3 (TGU) and SW4 (TGD)
SW2 – Vibrato mode, SW5 – robot mode
LED to display the voice level input
ON/OFF slide switch for power supply
Audio amplifier type LM386 with volume control preset
PBT (Power Battery Terminal) connectors for supply voltage and speaker output
Power-On LED indicator
PCB dimensions 63 mm x 68 mm


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