Revisiting the PSS-790

Yesterday I spent some time tackling the mess in my attic, and classically uncovered a bunch of really useful bits underneath the debris. Somewhere amongst them was a trusty old companion, a PSS-790 that I modified in 2011/2012 and used extensively in my Ginko project:

PSS790 - 3.jpg

The PSS-790 is a fairly straightforward amateur keyboard, it has mini keys with no velocity, 99 presets of Yamaha’s “Advanced Wave Modulation” sounds and rhythms, a basic song editor, assignable percussion pads and the Vector joystick – for a keyboard that is almost a toy, it has some pretty ok features. The sounds are clean, some of them are interesting (like the theramin like 68 “Chorus” sound and 74 “Synth Strings” – yes I know them by number!!), the vector joystick allows for layering of sounds at the expense of polyphony and in a similar manner, there is a “Harmony” setting that has various instant chords and strum effects, but doubles up the voices used.

But the best thing about this keyboard is that it utilises Yamaha’s AWM technology – I discovered some years ago that devices that use the original AWM system will always make very good candidates for modification! This was actually the second PSS-790 I modded. For the first I used similar points, but limited myself to 8 switches in total – for the second I went all out with a 30 point patch matrix, breaking out all the pins of the AWM processor as well as unlocking some other interesting points. By patching something on the matrix, you effectively create a short circuit across the sound brain of the keyboard and all kinds of exotic results follow.

PSS790 - 2.jpg

My original mods

As well as the brain scrambling patch matrix, I included a patch socket that seems to guarantee drone effects of some flavour (different for every point on the matrix and sound loaded on the keyboard) and another socket that results in automatic aleatoric chaos! It’s hard to tell what the drone patch actually does, it seems to make notes hang with envelopes open, or it could be scrambling the synths reverb – polyphony plays a part in the results you hear, so the reverb is probably just some hacky voice envelope behaviour as opposed to an actual processed effect.

The AWM approach is to use very short samples of real world instruments, and then combine them by layering, re-pitching and amplitude enveloping to produce the variety of sounds on the devices using the technology, it’s effectively a very basic form of granular synthesis – I think that what makes these instruments interesting to modify is all of the described functions of AWM are handled by a single or pair of large custom chips. So when you cross the nerve endings of the instrument, you can get pretty spectacular results like obscure enveloping, samples playing in reverse or choppy patterns and odd sample layering combinations. The PSS-790 isn’t the craziest of the AWM instruments I have modified (I think the PSS-31 has to hold that title) but I think it is by far the most musical results I have achieved from a bend project PERIOD. At least I think so – my definition of music may be quite squiff compared to yours!

There are a number of things that work really well with the modified PSS-790, one of them being that the standard controls across the keyboard tend to work as normal in combination with the mods – so for example it is very easy to get melodic drones going with simple patches, once you have them you can often use the pitch, vector and harmony controls to manipulate them. Another thing that sets this system apart from many others is that it behaves very predictably, if you load a sound and patch something in, you will always get the same results (with the exception of the chaos patch!!).

The downside here is that you have 99 sounds and a huge amount of possible combinations in the patch matrix, including multiple stacks on one socket – not everything sounds good and trying to remember what definitely does is like trying to memorise a piece of music in itself. Melodic layered drones, glitched squelch and heavy distortion are all very possible with slight changes to patch and settings – playing live with this keyboard was always a real challenge!! However – for its capability to produce mesmerising sounds and an endless serving of surprises, I will always have a soft spot for this instrument!

I will try and find the time to fluff this article out with some samples soon

Hello, I’m not dead…

Aaaaaargh! It’s almost been a year since I changed anything on this blog!!

Well, many things have happened – maybe I have an excuse, maybe not. I worked at Modal Electronics from April 1st 2015 to May 1st 2016. Working at Modal was fun and a good learning experience, but ultimately it was all consuming and I was feeling a real weight on my shoulders for having to give up many of the things I loved doing, and eventually decided that being normal just wasn’t for me. Anyway, between then and now plenty has happened…

One interesting outcome from my time at Modal was that I began selling off much of my modular noise making gear as I didn’t have the time to work on music or gig as I did before. I ended up with a reasonable stockpile of cash as a result and being a total man of the moment, I decided to actually buy something that I didn’t dream I would ever have the opportunity of owning – which was a pretty fully featured Hordijk modular system! Now if you don’t know who Rob Hordijk is, it’s probably a little too much to go into here, but it should be enough to say that he is probably the biggest inspiration in both my design and my musical composition over the last couple of years. I contacted Rob in September 2015 and there was a 6/7 month waiting list to get a system (they are entirely hand made by Rob right down to the etching of the PCBs!!). I eventually collected my new system a week after I departed Modal in early May. I was experiencing some personal turmoil over forking out most of my savings for something as I was effectively unemployed, but I travelled by coach to Den Haag in the Nederlands to collect the system and kept reminding myself on the way that it was my dream setup, and I had been waiting a long time for it. Since I got it home I haven’t looked back, and hey – there’s plenty of flavours of super noodles to choose from 🙂

As you might have guessed I have now invested a lot of time into my new instrument. Over the last month I used the system for two solo gigs and on a recording I will share in another post. I am now working on a release with Difficult Folk in Berlin which should be ready pretty soon now. Anyway, I have plenty to write about the synth but don’t need to get it all in here. For now here are some pictures:

Here is the system with its father, Rob Hordijk:

Hordijk - 1

And here it is patched up at home:

Hordijk - 1 (1)

I am making a real effort now to become self sustainable with my own creative work, and I have a passion and ambition to continue working with electronic design. Most recently I have been working hard on a new workshop project that is OH SO CLOSE to being finished now 🙂 I’m not quite ready to share all the details, but it is going to be a nicely featured and fairly unique noise instrument that I feel safe to say has some strong design elements. The main aims of the project are for it to be educational, flexible, stand alone and expandable. I do have a little teaser, as I used my prototype (built into a £1 lunchbox) in this little set with Matt Lovett at Cardiff: MADE on the 11th of this month, I also used my Benjolin (another of Rob’s concoctions) and a homemade delay of my own design, so see what you can pick out:

Other than that, you will have to wait for a proper reveal! 🙂


Something I am Working On

I have been fiddling with filter designs lately and ended up knocking together a pedal / standalone unit for a prototype/demo. It is pretty fun, but could use some tweaks:


Yeah the knock-off Hammond case is held together with tape, it is because it is a knock off and no fault of my own!! Since I took the photo I replaced the tape with tape of a better colour.

Currently the unit has the following specs:

  • Sallen-and-Key topology design, low parts count and pretty good sound.
  • 2-pole Low Pass Filter with nice gentle slope.
  • Film capacitors for the RC section seemed to sound better, might have been my imagination!
  • Vactrol based voltage control, pingable (is that a word?) and easy to connect external modulators
  • Internal triangle wave modulation, 60 seconds to 1 second cycle time 🙂
  • Runs on a pair of 9V batteries


  • Filter Cut-off
  • Filter Resonance
  • LFO Rate
  • LFO Depth
  • External CV input

Here is a vid and sound clip playing with some other battery powered bits:

Yeah the vid could be better, but it definitely sounds great, I have been using it as part of an effects loop with my modular setup recently and it really delivers!!

Improvements I would like to make:

  • Gain compensation for more resonance, at the moment it distorts before the Q gets to a nice whistle – I presume this is handled in other filters by adaptive gain compensation, but this is just a guess.
  • I think a pre-gain control could be nice, would be good to be able to overdrive the filter a little. I don’t know if this would sound good yet, but I did notice that the filter behaves quite differently to different levels of input. Perhaps a pre and post gain control?
  • HPF mode should be easy to implement also but needs a slightly complex switch.
  • Some minor improvements for maximum LFO depth and filter frequency range would be good (and easy to implement).

Adam Walton/BBC Radio Wales: Science Cafe

I will be making a short pre-recorded appearance on BBC Radio Wales tonight at 6pm as part of Adam Walton’s show “Science Cafe”. I am talking briefly towards the end on analogue synthesizers in the contemporary digital world and a little on my compositional approach involving Chaos Theory.

The show is also featuring some discussion on the Ambisonic sound system at USW City Campus from Tim Land and its creator Simon Edmonds. Matthew Jackson is also making an appearance talking about a fully featured digital synthesizer he has been designing as a commercial product, building upon open-source technologies.

New/Old Modular Case Total Organ Transplant

I recently won a second hand case in a online competition hosted by Muffwiggler forum. The case was previously owned by forum member Strettara, he posted it to me from Italy. Oddly enough, he used to live in Newport where I live now and the case was exactly what I needed, portable and exactly the same slightly odd size as my previous case.

Yesterday I got to work making some minor structural improvements and transplanting the sketchy linear power supply over from my old modular setup – it was a tight fit but fit it did! Not without the usual blood, sweat and tears hands on DIY usually bears for me of course. Here are some pictures of the ordeal, the patient has made a remarkable recovery from the surgery, some would say miraculous!: (left click to enlarge)

And of course a short video: