It was a long time ago - but basically. Individual oscillators (based around 555’s) all having their clock rate determined by the pot . These square wave oscillators were connected directly to the gate array ic (which is SMT , so that also presents its own challenges) It’s not for the faint hearted - ie not like a simple mod to a 606 etc
See reply to the other comment regarding pitch . The ROM replacement is a currently available kit from HKA . Kinda cool , has about 6-7 rom sets in there. 707 , 727 , DMX , LinnDrum , 808 , 909 from memory. Worth checking out
@@mikuspilatus OK, and is the pitch of the HKA kit sounds also altered when selected ? Are all the pots the same value ? And which value did you choose ? Also, what are all those switches for at the left of the TR ?
Yes , the pitch of the selected sounds are altered by the pots . The value of the pot is not critical as you can adjust the frequency range of the 555 by altering other components . The switches control circuit bends - these smash bits of samples together
Nice work ! Any chance you could share your notes about these mods so that I could try to replicate them on mine ?
same same! How is this done? Beyond the obvious extra pots added, is this a ROM replacement?
It was a long time ago - but basically.
Individual oscillators (based around 555’s) all having their clock rate determined by the pot .
These square wave oscillators were connected directly to the gate array ic (which is SMT , so that also presents its own challenges)
It’s not for the faint hearted - ie not like a simple mod to a 606 etc
See reply to the other comment regarding pitch .
The ROM replacement is a currently available kit from HKA . Kinda cool , has about 6-7 rom sets in there. 707 , 727 , DMX , LinnDrum , 808 , 909 from memory. Worth checking out
@@mikuspilatus OK, and is the pitch of the HKA kit sounds also altered when selected ? Are all the pots the same value ? And which value did you choose ? Also, what are all those switches for at the left of the TR ?
Yes , the pitch of the selected sounds are altered by the pots .
The value of the pot is not critical as you can adjust the frequency range of the 555 by altering other components . The switches control circuit bends - these smash bits of samples together