Circuit bent Yamaha PSS-780

September 22, 2011 · Posted in Uncategorized 

Analog Chorus Hacked to reveal sweet LFO, which is then patched into the Pitch-Bend wheel for Pitch LFO. Also can be patched into the drum circuits for unique Drum Pitch LFO……

Loads of Glitch Mods for the Digital Drum machine section, including Pitch Modulation Knobs (Pitch down & Pitch Up ‘Over-Clock’ Knobs), Tonal Distortion / Ring Mods, Glitch & Phat Modulating Bleep Tones / Bass Tones…

Description of the PSS-780:

The Yamaha PSS-780 is a five-octave (61-key) small-key keyboard, and was a very sophisticated keyboard when it came out in 1989.

The keyboard uses a 2-operator FM Synthesizer to produce 100 pre-set voices, and also offers manual control of some (but not all) of the synthesizer parameters, so the user can create their own sounds. Five user-defined sounds can be stored in memory with single-button access. Percussion is PCM (sample) based, and can be played manually using the row of pads in front of the keyboard. A total of 32 percussion sounds are available, selectable in four banks of eight, and custom rhythm patterns can be created and looped using the “Custom Drummer” feature.

There are also 100 pre-set rhythm and auto-accompaniment patterns, each with an orchestrated ending and three different fill-ins available.  The fill-ins are orchestrated, and are activated using the three large purple pads in front of the keyboard, and are therefore very easy to hit at the right moment during a live performance. The three fill-ins can also be used as Intros, but when used like this they play percussion only with no orchestration, and the orchestration begins after the Intro. With the “Synchro Break” function enabled, you can also add your own manual fill-ins or a drum solo (!) using the drum pads during the performance. This works with either the pre-set rhythms, or your own “Custom Drummer” loop.

There is also a five-track sequencer, which allows independent recording of each track using different voices (including user-defined voices) with simultaneous playback, together with auto-accompaniment or custom rhythm pattern, so complex orchestrations can be achieved.

There is also a pitch-bend wheel (configurable range between 1 and 12 semitones) and lots of other features and effects which I won’t detail here – get the Manual if you are interested.

While the PCM rhythm sounds each have a defined stereo “position” the voices are fundamentally mono, and the only stereo effect comes from enabling the “Stereo Chorus” function.

The built-in speakers are remarkably good (as expected on a Yamaha), but my example has an unusually hissy amplifier, and there is also a constant high-pitched whistle on the output. The hiss gets even worse when “Stereo Chorus” is enabled. I have owned my PSS-780 since I was bought it for Christmas in 1989, and it has always had this noisy output, so I suspect this is a design flaw on the PSS-780.

There is an interesting easter egg in the PSS-780’s firmware. If you hold down the top two white keys at the far right-hand end of the keyboard while switching on the power, the keyboard enters what I can only assume is some kind of diagnostic test routine. I won’t spoil the surprise for you, but try pressing some buttons and see what happens! Don’t worry – you can restore normal operation by switching off and back on again.

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