Modifications for Sample based Drum machines (707,Linndrum etc)

Design Concepts
1

Hey all.

I used to do a whole heap of mods on roland TR-707 (&727) drum machines.. mainly replace the clock frequency of each sound with a CMOS 555.. I can’t remember what was the range of frequencies that they were driven up to, but at a guess 100hz - 20khz. I also used to circuit bend them for people..

www.myspace.com/mikesmodifications

I was thinking about doing a special mod, which used a core to drive the 10 clocks. (For myself, not for sale)

And have these driven by say, 10 rotary encoders..

Stick a few buttons on the side, to access diffferent options etc…

THEN - and this is the big then..

Make some software controlled LFO’s & Midi clocked Envelopes etc, use the buttons to access different options like LFO rate & LFO Depth etc..

Even make the pitch of the drums controllable by midi.. so even though they might not be able to be triggered by midi (Assuming the drum machine was running in pattern mode), the pitch could be dealt with in all sorts of fancy ways.. even maybe ring modulation.

So my few questions are - If there is 10 clock signals being spat out by the core, and 10 rotary encoders + 4 buttons + 4 leds, what is the max frequency that the 10 clock signals could be? Could they be driven up to 20khz or more?

How many of you out there own 707’s or 727’s or TR-505’s (Which are very similar), or for that matter, LINNDRUM’s or maybe even Oberheim DMX’s & DX’s?  It might even be able to be applied to the EMU Drumulator.

Then, out of that bunch, how many would like to embark on this sort of project? Not many I guess, but have a listen to the 707 samples on my myspace.. some of it is (obviously) from the circuit bends, but in combination with the pitch mod’s really rocks.

My knowledge of C is pretty limited, and i’ve just got a few books to help me along the way.. any takers?

Much regards

Mike

Modded 707.JPG
Modded 707.JPG1600×1200 523 KB

The 8 bits.JPG
The 8 bits.JPG1600×1200 361 KB

2

How many of you out there own 707’s or 727’s or TR-505’s (Which are very similar), or for that matter, LINNDRUM’s or maybe even Oberheim DMX’s & DX’s?  It might even be able to be applied to the EMU Drumulator.

I have a TR-707. Yeah!

Then, out of that bunch, how many would like to embark on this sort of project? Not many I guess

You’re right. I want (and I like) it in his original condition. Some things should become classical without getting any “mods”.  :wink:

As long as it works I’ll never open this device.

greets

Doc

3

I’ve got a DX, but the only thing I’ve always wished it had was a way to access larger capacity chips which could load more than one sound without swapping out EPROMs. I think I may even remember someone doing a switched piggyback EPROM board thing or something with a couple sounds, but I may be imagining it (I’m getting tired).

Had a 505, gave it away and wish I hadn’t. :frowning:

George

4

I’ve got a DX, but the only thing I’ve always wished it had was a way to access larger capacity chips which could load more than one sound without swapping out EPROMs. I think I may even remember someone doing a switched piggyback EPROM board thing or something with a couple sounds,

My SCI Drumtraks has this.. it’s a larger eeprom with a rotary switch to switch (What I guess) the MSB’s for most of the sounds..

It’s very handy.

As for 707’s and ‘classic’ in the same sentence.. thats funny.. But I feel for you.. If someone wanted to ‘mod’ my Prophet5, I’d Kill them.

Just that I own about 5 TR-707’s.. Most of them i picked up for $20 - $100.. Also, while they\ sounds are ok’ish, they sound 1000x better when you can at least de-tune them.. the clap sounds much better slightly lower, the cowbell too.. The kick is pretty boxy, but does sound better lower.

Regards

Mike

5

TR lovin in the house.  My 707 gets fed through a -lot- of effects, and also is the trigger sequencer for my Simmons SDS-8

6

I own a 505 which HAS to be modded, so yes i’m in for a new venture into unknown terratory :o

Allready got a lot of cinch patch bays etc…but driving each sound with a separate 555 timer was for me to much of a hassle…So if there is a MB way to this, that would be nice.

7

So does anyone know what the core is capable of with regards to making 10 square oscillators with a bit of software controlling the frequency + LFO’s ?

I’m guessing this is software dependent, but what ballpark figures are we looking at? 1Khz ? 10Khz ? 100Khz ?

Regards

Mike