ST808
This piece uses a combination of the two following schematics.
-I’ve replaced the relays from schematic 2 with transistor switches.
-I only installed one channel
-I didn’t use the 7408 or 4016 ICs shown in schematic 1.
I’ll include an updated schematic when I finish the piece.
This model uses the ubiquitous 555 timer IC
and the ultra simple, super useful 4017 counter IC.
The effect is a glitched out sounding, programmable sequence.
There are 8 steps in the sequence and each can be turned ON or OFF.
As the sequence runs, it advances one step at a time, 1 thru 8, then repeats.
When a step is set to the ON position, it activates 2 effects in the Speak&Spell for the duration of that step. The 2 effects are a tone generator and a “hold” effect.
The schematic above shows how to locate these bends.
“Hold” grabs whatever sound is playing and loops a snippet of that sound. So, if the Speak&Spell was saying “Spell the word PONY” and you activate the “hold” effect in the middle of “PONY”, it would sound like…..”Spell the word POOOOOOOOOOONY”.
One of my favorite SpeakandSpell bends is the “loop” effect (see schematic). This generates random loops that repeat indefinately.
I’ve found that interesting rhythms can be created by activating the “loop” effect, and then pulsing the “hold” effect over it. The “loop” provides a tonal backdrop and “hold” grabs bits of sound from the “loop”. If “hold” is rhythmically pulsed (using the 555 timer) it will grab sounds at regular intervals and make a constantly changing, rhythmic effect.
The tone generator effect accentuates the rhythm and can sound nice if the sequence is changed often. If it just pulses regularly (without any variation) it starts sounding like an alarm clock.
The sample below should clarify things a bit.