Novation Supernova II & Nova II – 24 Voice Expansion Project

Novation Supernova II / Nova II – 24 Voice Expansion Project

Novation Supernova II  / Nova II – SIIEX24 24 Voice Expansion

The Sector101 SIIEX24 card is now available!

Please visit this page for details:
Sector101 SIIEX24 Page


The photo above is of the rare Novation SIIEX24 24-Voice Expansion Board. This board plugs into the SuperNova II & Nova II and will increase the polyphony by a further 24 voices. SuperNova II units that have this expansion installed are known as the “Pro-X”. Nova II units that have this installed are known as “XL”.

There is also a 12 voice card available known as the SIIEX12.

The card in the photo was in my hands for just a short time. It was fitted to a customer’s motherboard when it arrived for a DAC Replacement job.

Being a rare item this card will have very high prices on the likes of eBay. At the time of writing there is a 12-voice card on eBay with a price of around £325. On a lucky day you could pick up a fair condition Supernova II for that. The SIIEX12 12-voice card is simply a cut-down version of the SIIEX24 card with three of the DSP chips missing.

This guy was very happy to finally get his 24-voice card and made a YouTube video describing the card and showing how to fit it. Please see the video HERE

The SIIEX24 Project – A New Hope

Having developed several expansions for other synthesizers over the past 10 years I have had an on-and-off idea for recreating this board. It looks scary with the six 144-pin DSP chips suggesting a lot of connections to figure out. After studying the Supernova II motherboard’s DSPs connections I found that not all the pins are used. Also one side of the 50-way motherboard expansion connector is mostly Power & GND connections. This card may not be as scary as I first thought. My on-and-off idea for recreating this board has been nudged firmly in the ‘on’ direction!

At the time of writing I have a 12-voice coming by way on loan – thanks Daniel 🙂

I will study this board when it arrives to learn how it is wired and create a net list of connections. Also the board dimensions and connector location will need to be measured. I will also attempt a 12-voice to 24-voice upgrade on the card by adding the missing components.

6th Dec 2017 – The Card Arrives!

It arrived within a few days. The photo below shows Daniel’s card:

Novation Supernova II  / Nova II – SIIEX12 – 12 Voice Expansion Card

The 12 voice card was more useful to me than the 24 voice as I could see all the pads that needed a connection on the locations of the missing ICs. After 2 weeks with the card I have (hopefully) gathered all the info I need to recreate the full expansion card.

Six Card Configurations

As an experiment I disabled the “DSP select” signals on my SuperNova II motherboard to fool the SuperNova II into thinking the DSPs on the card were faulty. Normally if one of the onboard DSPs fails to boot then the unit will hang and a series of LEDs will be lit under the Part Edit section.

I found that if a DSP fault was emulated with the expansion card the SuperNova II will still boot and show 24 Voices. Depending on which DSP was disabled the SuperNova II would show either 24, 28, or 32 voices. This means that an expansion card could be built in six different ways to be 4, 8, 12, 16, 20 or 24 voice depending on how many DSPs are fitted to it – it is not limited to the normal Novation 12 or 24 voice configuration.

As a trial I added one extra DSP to the board to see what would happen. I placed the additional DSP on the board with all the support components it needs. The SuperNova II reported 40 Voices on boot so it recognised the extra DSP in place. A test of the polyphony showed that the full 40 voices were present. Next job was to place all the DSPs on board.

12 Voice Expansion upgraded to 24 Voice

With the board fully populated it was time to install and test. On boot the SuperNova II showed the full 48 voices available.

Supernova II with the full 48 voices

Testing the polyphony showed that the full 48 voices were available. I did this by setting the Release fully up and hit a low note that would sustain indefinitely. Whilst it was playing I kept hitting a higher note until the low note disappeared. It took 48 hits on the high note until the low note cut out.

20th Dec 2017 – PCB Design

I’ve spent a bit of time doing the board layout over the past 2 weeks and almost have it finished. The underside of the board has no components and this is the side that sits face-up when installed.

I have used a 6 layer design for this board over my usual 4 layer designs. This allows me to keep the internal 3V3 and GND planes intact without cutting them up for signals that I could not route on the outer layers.

The datasheet for the Motorola DSPs recommend 6x 100nF decoupler capacitors for each IC so I have increased the total quantity to 34 – an increase of 10 on the Novation card.

I’ve been toying with some silkscreen designs for this side of the PCB and have two candidates so far:

Silkscreen Candidate 1
Silkscreen Candidate 2

I’ll probably toy with some other designs as well. Once I have checked the PCB connections the design will be sent off for manufacture in Jan 2018

20th Jan 2018 – PCB Design Modifications for Heat Dissipation

Having recently upgraded several 12 Voice SIIEX12 boards to the full 24 Voice spec I have noticed quite a lot of heat generated from the fully populated board when it has been powered up for a short time.

Besides the 6 DSPs generating their own heat, the power regulator circuit on the board kicks out a fair amount of heat on its own.

The board is powered from the PSU 5V rail then gets dropped to 3V3 through a regulator circuit for the DSPs. Novation have designed the board to spread the heat from the regulator circuit over a larger area by using several low-ohm resistors in parallel to drop the voltage before it hits the 3V3 regulator. Despite this, the 3V3 regulator gets quite hot and there is not a lot of copper heatsinking where it is mounted. The regulator datasheet states a maximum of 1 Amp of current and when there are 6 DSPs mounted on the board the current goes a shade under this.

To help dissipate the heat on the new board I have decided to make the board design slightly longer toward the cooler side of the motherboard. Also, a higher rated 1.5 Amp regulator will be fitted in the extended area with full copper planes on both faces of the board to help with heatsinking.

Board Revision C – Top Side
Board Revision C – Bottom Side
OEM Vs Sector101 Board Size Comparison – Component Side
OEM Vs Sector101 Board Size Comparison – Solder Side

Although the bigger board design fits comfortably in the Supernova 2 I was concerned that it may not fit the Nova II. I got in contact with a Nova II owner who kindly photographed the inside of his unit. As you can see from the photo the Nova II uses the same motherboard as the SNII but does not have the SNII’s Output 1 & 2 fitted. Many thanks to Andreas Schoter for taking the photograph of his Nova II 🙂

Inside the Nova II

15th Feb 2018 – PCBs arrive: First Build Test

Sector101 SIIEX24 Expansion Cards

The PCBs arrived earlier this week and with all the parts ready it was time to do the nail-biting first build.

The easiest way to build the card was in this order:

  1. Regulator and support caps
  2. 6x Big 5R6 Resistors
  3. 6x DSP ICs
  4. Small 0805 Resistors & Caps
  5. Connector

Time to lift the hood on the SNII and plug it in.

Sector101 SIIEX24 Expansion Card Installed

With a sigh of relief the SNII gave me the full 48 voices. Without a schematic for the original board the only way to trace it out was using a multimeter with a stack of notes and drawings.



With the design proved it’s now time to aquire more parts and start making some stock 🙂

15th March 2018

The Sector101 SIIEX24 card is now available!

Please visit this page for details:
Sector101 SIIEX24 Page


// END


8 thoughts on “Novation Supernova II & Nova II – 24 Voice Expansion Project

  1. I am looking to get a Supernova II Pro-X but it’s mainly base units out there, and I have not seen a 24 voice expander for a dog’s age. If and when I can afford a Supernova II, I would definitely be after a 24 voice expander if it needs it. Please pursue this. Thank you. PS–I am a previous customer having gotten one of your SY-85 RAM expanders a few years ago. Also looking at a Sup right now that needs a DAC, so, fingers crossed.

    Liked by 1 person

    1. Hello Jani.

      For information. your card for supernova 2 will be ready when? Other request. I have a sy99 I look desperately for version 1.30 of the seq rom also to upgrade to version 1.57. I have the firmware and firmware 1.57 of the eprom. on a plcc84 it does not work. on a site you speak: Do you have the CPU code dump? I’ve been talking to Brian (Sector 101), he’s not so slow for the SY99. But there is also a H8 / 536 16MHz version that is cheap enough ($ 20 on eBay) to try as a test.

      Do you find the worry? because on some sy99 there is a QFP80 in version 1.57. Can not find a QFP80 adapter in PLCC84. You are my “hope” to find out how to pass my sy99 version 1.30 seq rom and 1.57 format PLCC84.

      thank you in advance

      Garanti sans virus.

      2018-02-13 20:50 GMT+01:00 :

      > Jani Kervinen commented: “Hi, Please continue with this project. I have > supernova 2 rack and it definitely needs this expansion. My unit is basic > unit, without any expansion in it. Thanks, Jani” >


      1. Umm I’m not sure what you mean. I have no idea when the card is ready for purchase. I just mentioned I want one too. I’m not the card maker or anything related to this sites actions. Just a potential customer 🙂


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