The LTC1799 board from circuitbenders.co.uk is a must for devices that are pitch controlled by a crystal or ceramic resonator rather than by a resistor. The LTC1799 mod is only a tiny bit more challenging than replacing the pitch resistor in a toy circuit. The main difference is finding a suitable 2.5 to 5-volt power source to run the tiny add-on circuit. Lucky for us, the Yamaha DD-14 has both power and ground close to the CR2, the ceramic resonator we will be removing, and replacing.
LTC1799 Installation notes for Yamaha DD-14
Step one: Wire up your LTC1799 board as per the instructions at circuitbenders.co.uk – I used a 50k pot, a 100k crashed the machine at around 70k
Step two: Locate and Remove CR2, it has 3 legs unlike some other ceramic resonators, crystals, or coils so take notice.
Step three: Determine which solder pad from the removed crystal goes to the LTC1799 circuit.
(in the case of the DD-14, the pad closest to a dotted area marked IC2 seemed to work best, this is also a great place to mount your little LTC board).
Step four: Using a multimeter, find suitable power and ground for the LTC1799 (2.5 to 5 volts, see image)
Step five: Test your machine; you may need to adjust the tiny trimmer on the LTC1799 board to get the best results.. be careful as this trimmer spins 360 degrees and can easily break.
Step six: Mount your LTC1799 board with two-sided tape, hot glue, or whatever your preferred adhesive is.
Circuit Bending notes on the Yamaha DD-14
Ceramic Resonator
- CR1 controls the computing speed, you can drop an LTC1799 here but the results are minimal and cause the machine to start slow, and react slow. The bonus is you can pitch down the stock tempo.
- CR2 controls the pitch, this is where it gets interesting.
ROM IC
- Pins 1 & 32 go to 5 volts; skip them when making a patch bay or attaching switches.
- Pins 16, 22, and 24 go to ground, you will only need one of these.
- All other connections are interesting; connect pins to ground for testing, then to each other.
Drum Pads
- The pads can be triggered by 5 volts
- When using a button or a switch, the sound loops continuously.
- You can wire the pads to jacks and create external triggers (piezo to anything and smash).
- CV seems possible, but I have not experimented with that yet.
Fun wiring mod for the LTC1799
While not really a mod, you can always use a smaller pot in series with your main potentiometer. I used a combination of a 50k and a 5k and really love the ability to fine-tune the sound as the machine starts to glitch out and change the rhythm. I also added a photocell that can be switched on to take the place of the 5k pot. The photocell is nuts! Thanks for the tip on that, Jørg Peltzer!
