Yamaha Triple Pedal Connector

Introduction

After buying my Yamaha P85 digital piano, I was not satisfied by any of the commercial pedals available. You can buy high quality single pedals (i.e. the Yamaha FC-3), and you can buy a cheesy stand-integrated triple pedal (i.e. the Yamaha LP-5), from Yamaha. You can buy a CME GPP3, but it has gotten hammered in user reviews. Unfortunately, Yamaha does not provide a specification for their pedal interface, so I have done a little bit of reverse engineering to help you wire up some proper pedals for your Yamaha. Note: As long as you don't plug anything powered into your piano pedal jack, I can't think of any way you could possibly damage the electronics of your piano following this tutorial. That said people can find very creative ways of breaking things, and NEITHER THE POSTER OR THE VAGUELY DEFINED SOCIAL ENTITY KNOWN AS THE DIY KEYBOARD PROJECT IS RESPONSIBLE FOR WHATEVER HAPPENS WHEN YOU PLUG THINGS INTO YOUR DIGITAL PIANO.

The Connector

The [connector] used on the Yamaha P85 (And perhaps other pianos) is a 6 Pin Mini DIN connector, which is used for PS/2 PC mice and keyboards, among other things. (It probably won't fry anything, but please resist the temptation to plug your Model M into your expensive digital piano) I'm not sure if the pin numbering in this diagram is for the piano (female) or for the cable (male). The following discussion assumes this diagram is looking at the female connector at the back of the piano. Reversing things will only change which pedal does what; no danger.

MiniDIN-6_Connector_Pinout.svg

The Signals

Pins 5-6 and the connector shield are connected together internally to the piano. Let's call this voltage GND. It is probably also connected to the piano's internal metal chassis, if there is one.

The remaining four pins are shorted to GND individually or in combination to signal that the corresponding pedal is depressed. i.e. you need to use pedals that are normally open switches. This is 3V logic, and the internal pull-up resistors are large valued, so you're unlikely to damage anything in this process.

Pin 4 is the Una Corda Pedal. Note that, at least on the P85, this is results in a subtle change in timber that you might not notice at first if you're distracted by the numbers on your Multimeter.

Pin 3 is the Sostenuto Pedal. If you've gotten this far, you probably know what this does. Kudos to Yamaha for implementing the Una Corda pedal properly; I hear a lot of manufacturers bungle this.

Pin 2 is Full Damper.
Pin 1 is Half Damper.

There may be more to the proper usage of Pins 1 and 2. Their marketing language is a bit ambiguous about continuous vs. whatever "Half-Damper" means. I may just be two switches that close in succession as you depress the pedal. Or perhaps you actually hook up a potentiometer with some nice taper in some way to get smooth pedal action. Edit this if you figure out more.

Usage

I recommend plugging Yamaha's high quality single pedal (FC-3) into the sustain jack provided on the back of the piano. This'll give you a really nice smooth damper pedal action. The other two pedals are simple ON/OFF switches, so you can get away with any old cheap off-brand pedal as long as it feels good on your foot. Bolt them together into one rugged assembly however you want. The damper works with the una-corda as you'd expect it to, BTW.

Kudos to Yamaha's Engineering Dept. for making an awesome (well, for 5-7 layout anyway) piano, not going out of their way to obfuscate the control signals electrically, and using a standard connector.

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