Special Pages


The Simple Pseudo-random Sound generator

Courtesy/Thanks to: Joe Paradiso

Description: This circuit runs on a single +5 Volt supply and drives a speaker directly. The sound that's heard originates from a 555 timer in one-half of the dual-555 chip (U1), the 556. This 555 circuit drives a 4024 CMOS 7-stage binary counter U2, which produces 7 subharmonics below the frequency of the 555 (quiescently set to be around 10 kHz through the resistors and capacitors at pins 1 and 2 of U1). An 8-1 multiplexer/demultiplexer, the 4051 (U3) selects one signal out of the 7 available subharmonics from U2 and the original clock signal from U1, and routes it through an NPN emitter follower bufer (T1), which is able to drive a loudspeaker, producing the sound that we hear (I've provided a line-level audio output as well for jacking into recording device inputs, decoupled with the 1 uF capacitor and buffered by the 1K-Ohm series resistor). Note that driving a loudspeaker directly off the Class A amplifier that T1 forms isn't good form without isolating the speaker from the transistor with a big (e.g., 1000 uF or more) capacitor (remember that T1 would still need an emitter resistor for DC bias), as the 0-5 volt square waves appearing at the transistor output have an average DC voltage of 2.5 volts, which does nothing but heat up the voice coil in the speaker. I get away with it here as the voltages are so low and the speaker isn't of high quality, but note that it's very poor form.


You need to be logged in to add a comment.

Editing and adding
You need to be logged in to edit and add files and urls etc.
Categories & Tags
Popular tags for this:

You must be logged in to add tags.

Inventory & Trading

You need to be logged in to administer your inventory

No one is selling this product at this time.

   Schematics for the Psedo random sound generator (MAS861)
   Sound example of the MAS861
   ¨Picture showing the assembled MAS861
   ¨Picture showing the assembled MAS861
   Another soundfile showing what the MAS861 sounds like.
Parts used
   NPN switching transistor
NE 556
   Dual Timer Circuit
HEF 4024
   7-stage binary counter
CD 4030
   8-Stage Static Shift Register
   Single 8-Channel Analog Multiplexer/Demultiplexer
   Single/Dual/Quad, 10MHz Single-Supply Op Amps
   Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Similar on Ebay