Roland S220 12-bit Sampler

Introduction In October 2018 I bought a 31-year old Roland S220 sampler for £70, with no photo of it working this was a bit of a risky purchase! Why buy one in the first place, given it only manages 4.4 seconds of sample time at 30 kHz and 12-bits? Even the disk drive is horribly unreliable and impossible to replace or even find blank QD diskettes for.

Well its that lo-fi sample sound that I am after, so I can sample some modular synth sounds and create bass lines and strings. I also want to develop a Quick Disk drive replacement using a microprocessor, which will store 100 sample banks in memory.

Worn Out 16×2 LCD

History The Roland S220 was introduced in September 1987 as an upgraded 16-voice version of the S10/MKS100 but with the same limited 256k byte RAM. It lasted about a year in production before the improved S330 was launched with 756k byte of RAM, so its a relatively rare sampler. The S220 received a new operating system with a lot of improvements over the S10 including 4-part multi-timbrality and up to 4 audio outputs and a good auto loop. There is an external trigger and arpeggiator, so it plays nicely with modular synthesizers.

My S220 I bought a new mains lead and carefully powered it on, after checking there were no internal issues such as damaged power caps. It booted successfully but the LCD screen was extremely worn out and barely visible, so a new green 16 x 2 OLED display from Raystar Electronics (Part Number: REC001602AGPP5N) was bought for £22.

It is a simple swap, the new LCD is the same size and the EL back light power can be disconnected from the PSU. The front panel has to come out to gain access to the LCD, and the interface wiring has to be desoldered from the old LCD and re-soldered to the new LCD. This is easy to do as the wiring unplugs from the motherboard, the LCD news careful alignment with the front panel bezel so all the top and bottom of the characters can be seen.

Roland L-109

I also bought a set of Roland sample diskettes, the L-109 Synth & Organ, as it has a rather nice Jupiter 8 and VP330 sample bank. This loaded successfully on the second attempt after I cleaned the diskette head and felt pad. Amazingly the QD drive works, although it is easy to do sample bank transfers over MIDI using the S10 Manager software.

Second S220 A couple of weeks later I bought a second S220 but this was in much worse condition . The electronics seem okay but the QD motor was permanently on and whining loudly, and the drive belt had melted. I did manage to reduce the whining and improve the head tracking but the Motor will not stop when powered on. So this S220 will be the “mule” for the QD drive replacement project.

Maintenance The lithium batteries were replaced in both samplers, they keep power to the 8K bytes of Performance Data held in SRAM. The power supplies were refreshed with all new   electrolytic capacitors, especially the 4700uf and 2x 2200uf reservoirs as they have been working for 30 years, along with lots of cleaning out of dust from the casings!

QD Drive Replacement  Part of the reason to buy a Roland S220 was to design and produce a QD drive replacement. The QD drive uses a single spiral track recorded onto each side of the diskette, and is half like a cassette and half like a 3.5″ floppy drive. It transfers data slowly at 100 kHz and is encoded in MFM format with 64k bytes each side taking about 5 seconds to load. Samples can be loaded and saved but also the disk can be read o provide the sound name and bank setting.

The drive replacement will use a micro-controller to read and write the data, a small OLED display and a SD card for storage. This project will take place in 1Q 2019 and it has its own dedicated web page here.

SSI2144 and SSM2044 Comparison

Overview In 2017 Sound Semiconductor launched the SSI2144 voltage controlled low pass filter, a re-engineered SSM2044. At AMSynths we have used both chips in our modules; the SSM chip in the AM8044 (2014) and the SSI chip in the AM8144 (2018). We also make adapter PCB’s that convert the different pin out of the SSI2144 to the SSM2044 pin out, this enables them to be a drop in replacement for synthesizers that use the SSM chip.

The SSI chip has a set of minor but worthwhile improvements and specifically the resonance control has on-chip control, and the Q control current for oscillation has been reduced from 425uA to 400uA. The Q control suggested external circuit is also slightly different to the SSM version.

So lets hear and see a comparison between the two chips with the same input signal at 50Hz from an Emu Systems Modular VCO, as I dial up the resonance from zero to maximum.

Original SSM2044 Here is the SSM chip manufactured in March 1987 notice the longer duration before oscillation comes in.

Re-imagined SSI2144 And now the SSI chip from 30 years later, notice the oscillation comes in quicker. In our modules we use the recommended Q external circuits for each chip, and we trim the onset of  oscillation when setting up the modules for customer shipment. So our modules will sound similar. In polyphonic analog synthesizer with a mix of SSI and SSM chips the resonance trimmers will need to be adjusted when a SSM is replaced with an SSI, or better still replace all the 2044’s.

Boss PH-2 into a Jupiter VCF

Introduction  The Boss PH-2 Phaser pedal contains two valuable Roland IR3109 OTA chips. This post explains how they can be carefully removed and used in the AMSynths AM8109 JP8 VCF or the AM8060 JP6 VCF module. The PH-2 was manufactured for nearly 20 years, from the early 1980’s until at least 2000 by Boss (Roland) and is available second-hand from 20 – 90 GBP depending on condition, try not to pay more than 40 GBP.

Customers following these procedures do so at their own risk and there is no guarantee of success made by AMSynths.

Buy a Boss PH-2 We bought this pedal on eBay in November 2014, it is serial number FN21896 and was produced in March 2000.

Stage 1 – Circuit Board Removal
The first stage is to remove the paxolin PCB from the pedal.

  1. Undo the 4x black posidrive screws in the base of the pedal.
  2. Remove the base plate and clear plastic protector.
  3. Pull the PCB out of the case, it is attached via a grey ribbon cable and 10 wires.
  4. Cut the wires and ribbon cable near the PCB and there you have it – the PCB with two IR3109 chips. Nice!!

Stage 2 – IR3109 Chip Removal

  1. The second stage is to extract the IR3109 chips from the PCB. We prefer to cut the chips out before then carefully desoldering the pins.
  2. Using a coping or fret saw cut around the two chips very carefully, you may want to remove some components by clipping them out with cutters, so that you get straight and safe cut lines.
  3. Now remove each IR3109 attached to the PCB as 2 separate sections.
  4. Mount the small PCB section in a pin vice upside down.
  5. Cut through the back of each PCB very carefully between each set of 4 pins. Make sure you don’t cut down into the IR3109.
  6. Heat the solder pads of the first section and using a pair of fine nose pliers gently ease the PCB section off the 4 pins.
  7. DO NOT OVERHEAT the Pins or IR3109.
  8. Alternatively you can use a de-solder pump and not cut the PCB into sections.

Note: We have found the IR3109 to be a robust chip which is not over sensitive to static or heat. But PLEASE take care! They also seem to last many years (decades in fact), it is rare for us to find one that has failed. Of course it’s worth testing your pedal before you extract the chips, so that you know the chips are working.

Stage 3 – Clean Up the IR3109

  1. Once you have removed each IC from the PCB section….
  2. Using de-solder braid remove excess solder from the front and back of each IC pin.
  3. Straighten up the 16 pins with fine pliers.
  4. Optionally use flux remover to brighten up the pins.
  5. Wash the chip in water if you do this procedure, and allow to dry.
  6. You now have a nice clean IR3109 chip!
  7. We usually put them in IC holders to protect the pins, and to enable them to be quickly fitted to a PCB.

Mistakes do happen!

  1. You may break an IC pin on removing the chip or the pin may break because it is fragile.
  2. Don’t worry, they are easy to repair.
  3. Mount the chip in an IC socket and feed a resistor wire into the top of the socket and align to the damaged pin.
  4. Then carefully solder the wire and pin together.

Jupiter One

Jupiter 4 Voice Card (dusty)

Introduction  I picked up a Roland Jupiter 4 voice card on eBay in late 2017 in good condition. In June 2018 I started a project to build a complete single Jupiter voice based around this card. The synth will fit into a Moog 60 HP case (another eBay find) with an aluminium front panel that replicates (most of) the controls of the Jupiter 4.

To create a fully working single synthesizer voice means a lot more electronics are required than just the voice card! The complex module controller card has to be replicated along with a LFO. The arpeggiator has been left off the synth as it requires the 8048 micro-controller, which means no programmabilty or presets either. The JP4 modulation capabilities have been retained and enhanced, with a 5-axis thumb joystick and a revised S&H circuit for the VCF modulation.

Voice Card This is an early 1979 D version of the card with a BA662 based low pass filter. The first job was to clean and dry the card and remove the metal guides. This reveals 4 mounting holes for the top of the PCB. The 4 green connectors are replaced with 9 pin SIP headers, so the card can be mounted to a new motherboard PCB. Some of the ceramic capacitors needed replacing and the trimmers will be replaced with high quality cermet Bourns trimmers.

A hack to the card to add a potentiometer to adjust the VCA Gain trim has been removed and a trimmer put back on the PCB. The card is spaced 12 mm from the motherboard. I am hoping the voice works, but I am sure there will be some repairs needed. The card has additional power supply caps mounted on the rear, which I have retained.

Module Controller The Jupiter 4 has a dedicated 5th card in the card frame to hold all the circuits that translate and mix the programmable CV voltages for the Voice Card. It also contains the CMOS based envelope clock generators. All these circuits have been put on the Motherboard PCB of the Jupiter One which measure 295 mm x 105 mm. The  module control circuits and Noise circuit has been retained, augmented with the S&H from the Jupiter 8 and revised LFO. Op amps have been upgraded to TL072’s and BA6110 OTA chips replace the BA662’s. This PCB is spaced 11 mm from the panel PCB and it contains the +/- 15V power rails, dervied from a switched and precision LDO power supply.

Jupiter LFO The LFO in the Jupiter 4 is on the main board and is very similar to the one used in the Jupiter 8. The JP4 version uses discrete FET switching and a two chip CMOS 2 to 4 address decoder, this is rather component intensive and a simpler approach is needed. Fortunately the Jupiter 8 LFO has the same waveforms and can be switched by a 4052 analog switch and then boosted before being used in the voice cards.

4-Way Switch  The Jupiter 4 relies on 4-way slide switches which are difficult to source, but we think we have the right one. It will mean make sub PCB’s to raise it up to the right level, but its the simplest electronic solution. The JP4 micro-controller decodes them into 2-bit binary signals for use in the Controller and Voice cards, which we can copy for the Pulse Width Modulation, LFO Wave Form and VCF Keyboard Follow.

Panel PCB The front panel PCB is 295 mm x 105 mm and contains 19 slide potentiometers, 4 rotary potentiometers, 2 rotary switches, 11 slide switches, the joystick and 4x jack sockets. The PCB mounts to the Motherboard via a set of 9 pin SIP sockets and headers. It is spaced 11 mm from the front panel.

Joy Stick The Jupiter One has a small thumb sized 5-axis Joy Stick mounted on the front panel. This controls the Bend (X axis) and LFO Depth (Y axis) with the integrated push switch acting as Gate On. This provides excellent control over 3 of the synths key parameters. The Jupiter 4 Modulation controls (next to the keyboard) have been retained so that the Bend Amount and LFO can be patched into the VCO, VCF and VCA.

Inputs & Outputs The external connections have been kept to a practical minimum to conserve panel space, so this is not a semi modular. There are inputs for CV and Gate, as well as the X and Y CV’s that over ride the joystick if plugged in (Bend and LFO Depth).  The 6.35 mm analog output jack is mounted on the rear of the 60 HP case, along with the 12V AC power supply input.

Missing Controls The lack of micro controller means there is no arpeggiator or presets or portamento. The Trigger Section of the synth therefore has not been included (like the Pro Mars). The transpose switch has been replaced by having a 4 octave range switch.

Commercial Option I may release the Jupiter One as a commercial project using new Jupiter 4 voice cards based on the BA6110 and a BJT expo generator to replace the ua726. DIY and completed synths may also be available. A two voice version is planned (same 60 HP case) with programmable presets and OLED display.

Emu Systems Emax

Introduction  I first bought an Emax rack sampler back in 1989 for £1200 and spent a lot of time making samples and trying to find the factory samples on diskette. In 1991 I visited the Emu Systems factory in California and tried to get a SCSI upgrade, but of course I had an early model and the upgrade was impossible. I then moved onto EII and EIII samplers in the 1990’s, whilst also finding an Emax SE HD keyboard which I used for a few months with a SCSI ZIP100 before I had to sell all my studio gear in 2003.

Emax 2018 Fast forward nearly 30 years and I found an Emax keyboard for sale at a reasonable price in Portsmouth and in good condition. I upgraded the LCD to a very nice blue OLED display that is an exact replacement, as well as a new USB floppy emulator replacing the rather old and damaged floppy drive. I have five USB sticks with two containing the Emu Systems factory library and the other 3 for my samples. I am now sampling a range of synths in the studio as well as using found sounds.

OLED Display is a Vishay O016N002CBPP5N0000 available from Mouser for £15, its an exact drop in, you just need to add 1 14 pin male header. It has a wide viewing angle, is very clear and not too bright.

All about the BA662 chip

Overview  The BA662 is a custom made DC controlled variable transconductance amplifier (or OTA) that Roland had manufactured by Rohm from the late 1970’s and is now obsolete. There are two types of chip with different suffices; the A version has been selected for lower offset than the B version. They are further classified by gain/gm. The BA662B can only replace another BA662B, whilst an A can be used in either application.

To quote Roland from the 100M Service Manual: Color has great importance in circuits of some models. However there is nothing mystical about the sound of the BA662, it is just a reasonable good OTA chip which is often carefully matched and selected.

Factory Selection The BA662 was used in places where close matching of the gain (gm) of the chip is important. Roland measured each BA662 and categorised them into 9 grades, ranging from 1 (low gm) to 9 (high) . They colour coded each chip with a small dot of paint on the top of the chip, the codes are:

  • 1 = brown
  • 2 = red
  • 3 = orange
  • 4 = yellow
  • 5 = green
  • 6 = blue
  • 7 = dark green or violet
  • 8 = grey or black
  • 9 = white

Roland required exact matching of colour dot in some applications (e.g. portamento in the Jupiter 4), and within +/2 colours for others. This need for measurement and matching was obviously costly and led to the BA662 being replaced by precision OTA chips like the IR3109, which were also smaller. The BA662 lived on in some Boss pedals but was ultimately retired.

BA6110  The more recent Rohm BA6110 OTA chip is similar to the BA662, albeit with a slightly different pin out, and it too is now obsolete. It is 3-7dB louder in the same circuit, has low offset (3mV) and low distortion (below 0.2% typically) when the linearizing diodes are used. We use the BA6110 in many AMSynths circuits (often matched), as they are still available, work well and are low cost. Other designers have used the LM13700 or even dual transistor based clones of the BA662 (which are lot moe expensive than using the BA6110).

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