I have listed this DX9 deliberately to playfully suggest it enjoys some of the functionality of a DX7. Yamaha did not make a DX97!

It is a DX9- with enhancements

It is in great ‘home use’ condition for a 40+year old synth and is all working well. The keybed responds well and the screen clear. It is a lovely example of this synth. A few age related marks but generally in very clean condition.

So why have I listed it as a DX97?

I have installed the experimental EPROM which has been written for the DX9 which restores the 6 operators and 32 algorithms of the DX7 which were disabled in the DX9. It can now play patches for the DX7 and a lot of the editing functionality of the DX7 is there and it’s lots of fun to hear how favourite DX7 patches sound - it seems brighter perhaps due to the absence of velocity sensitivity in the keybed.

Because the DX9 shares nearly the identical internal digital tone generation circuitry as the DX7 (Yamaha simply "crippled" it in firmware by turning off Operators 1 and 2 and limiting the algorithms), replacing the factory EPROM chip completely rewrites how the synth functions

Key Upgraded Features

If you look at the pictures you will see six operators visible and all 32 algorithms from the DX7 (as opposed to 4 operators and 8 algorithms in the stock DX9)

DX7 Patch Compatibility: You can directly load and play standard 32-operator DX7 patches via MIDI System Exclusive (SysEx).

MIDI Velocity Sensitivity: While the DX9's physical keyboard mechanism doesn't support velocity or aftertouch, the new firmware allows the tone generator to respond to dynamic velocity when controlled by an external MIDI keyboard.

Missing Envelopes & Scaling: It fully implements the DX7's Pitch Envelope Generator (PEG), portamento/glissando, and proper DX7-style operator scaling.

Other issues

Obviously this is not a DX7 and you won’t have the same controls but if you want a machine to host DX7 sounds played elsewhere (and you don’t use a DAW perhaps this is for you!

Only 10 memories function when in this mode- I have tried saving patches to 11-20 but they are not retained. As I said it is experimental! You can send DEXED sounds to it and it is happy playing them!

I did not write the code - it is freely available from GitHub and anyone is able to burn their own EPROMs and sell the upgrade.

If this ‘DX97’ synth is not for you I’d be happy to pop the original eprom back in making it a totally stock DX9. But I think it is quite fun to see and hear what it can do when unrestricted by the original software!

But for anyone interested in hearing a DX9 with DX7 patches then this will be a lot of fun to own!

Do get in touch with any questions. This synth will not be posted due to weight and size.. and I’d rather demo it in person with the new owner here in Warwick.