SP1200

Overview

The SP-12 Moves On The mid to late 1980's was a great time for dedicated sampling drum machines, and after the roar away success of the SP-12, E-mu Systems made a number of important upgrades and released the SP1200 in the summer of 1987. The key improvements are:

• An integral 3.5" DS/DD floppy drive
• 10 seconds of sample memory
• Full feature MIDI sample dump
• Everything else on the SP1200 is exactly the same as the SP-12.

12 High The SP1200 kept with the 12-bit crunch of the SP-12, as 16-bits was neither necessary nor cost effective (the 16-bit EIII had just been launched at $10,000+ in 1987). The SP1200 does away with ROM based sounds, and relies totally on a floppy disk based sample library which is loaded into RAM.

Sample Time The sampling time was upgraded to twice that of the SP-12 Turbo memory, providing 10.07 seconds of sample time within four banks of 2.5 seconds. The sample rate was reduced from the SP-12 27,500 Hz to 26,040 Hz, to enable the 384 Kbytes of memory to take 10 seconds of samples. There can be up to 32 user sampled sounds spread over the 8 voices, but no single sample can be longer than one sample bank (2.5 seconds).

The machine is very highly regarded in Dance and Hip Hop circles, for both its sound and beats..

Additional Features The SP1200 can store up to 100 patterns, 100 songs and has a 5000 note minimum memory for drum sequences. It also has a mono mix output and eight individual outputs, MIDI in/out/thru, SMPTE sync, and a metronome output.

Controls The front panel is littered with LEDs and buttons with eight chunky faders controlling the volume and pitch of each sound in the bank. A small button allows you to step between banks A, B, C and D giving easy access to the 32 sounds. Below each fader is a large button for triggering the sound, or selecting it for editing, and there's a global switch to turn the trigger's velocity sensitivity on or off.

The triggers are heavy and, with the passage of time, inclined to stick. You can get around this problem with the Repeat key which, when held down along with a drum trigger, causes the sound to auto-repeat at the current quantisation value, although it takes practice to start and stop the roll at the right point. Volumes are easily set with the faders and sound can be individually assigned to any of the eight outputs. Outputs can be either dry or passed through preset analogue filtering - undoubtedly one of the SP's popularity factors. Outputs 1 and 2 have fast decaying low-pass filters, 3 to 6 have static low-pass filters that slightly dull the top end, and 7 and 8 are unfiltered outs.

Step Edit One of the machine's clear highlights is the simple and intuitive step-edit mode, whereby sounds are added by stepping to the desired point and hitting the drum trigger. Although pitch and velocity can't be edited directly, it's simply a case of deleting the existing beat and replacing it with the corrected version. To this end, the SP1200 'Multi' mode temporarily splits your chosen sound across all eight triggers, at varying volume and/or pitch, making it ideal for precise edits or dynamic fills.

Sequencer The sequencer works in the familiar pattern-style, chaining short 'segments' into a song. Swing quantisation and tempo changes are easily added and the sequencer can generate or sync to SMPTE, MIDI or analogue clock pulses. It'll even synchronise to a tapping finger with the 'tap tempo' function.

Transferring SP-12 Samples The sound library from the SP-12 can be transferred to the SP1200 by connecting the cassette OUT of the SP-12 to the SMPTE IN of the SP1200. Power up the SP-12 and load the samples into the SP-12. Then power up the SP1200 with the DISK button held down. This places it into Cassette and MIDIDisk mode. Select Cassette mode (option 1), and then select either Seqs or Snds to transfer either sequences or sounds from the SP-12. When complete select option 3 MakeDisk, and save the samples to a diskette in the SP1200. You will need to name these sounds later on, and you cannot transfer the SP-12 ROM sounds.

Technical Overview

Architecture The SP1200 is based very closely on the SP-12 and Drumulator, and the technical architecture is very similar, being based on a custom designed micro-controller, a Z80 processor and multiplexed audio. It was also designed to be fully compatible with the SP-12 samples, which can be read in via the cassette interface.

The 8-bit Z80A processor runs at 3.3MHz, it reads the controls, writes to the display, and communicates to the outside world via an Serial I/O chip. It also runs the sequencing software. A CTC (counter timer circuit) is used for generating timing interrupts for scanning the controls every 1.2 ms and keeping the sequencer accurate and sync'd to MIDI or SMPTE.

The micro-controller is the E-mu magic which enables the sample memory to be read for each drum sample. The hardware design was all done by Dave Rossum, and this was the last solo project by Dave.

Sample Memory The SP1200 uses dynamic RAM memory for storing samples. The sample memory consists of twelve 32 Kbytes memory chips (total memory size of 384 Kbytes). The sample memory is actually 16-bits wide, and therefore has some de-muxing to fit 12-bit samples across all the chips. With a sample rate of 26,040Hz the SP1200 has 10.07 seconds of sample time, split over four separate sample banks.

Digital Sampling A 12-bit linear Digital Analog Converter (DAC) chip replays the samples, and is also used for sampling sounds via successive approximation. This saves the cost of an ADC chip. The sample input goes via an anti-aliasing filter to remove unwanted frequencies that are above half the sample frequency, the cutoff is brick walled at 42dB.

Operating System The SP1200 has diskette based OS, which is stored on all sample diskettes when they are formatted. The on board Boot EPROM instructs the micro-processor to load the diskette based operating systm into program memory, which is a mere 64 Kbytes in size and is used as the sequencer memory as well. Sample and sequencer memory are volatile and must be backed up to diskette before you power down the SP1200. The latest versions are OS diskette 1.2, Boot ROM Version B.

Micro controller This is made from discrete logic, although in the future this circuitry was encapsulated into one custom chip by E-mu Systems for the samplers made after the mid-1980's. The micro controller gets the sample out of memory, to the DAC and to the subsequent sample and hold circuits which are needed as the output channel is multiplexed.

Eight Voices There are a total of eight voice channels, through which the drum samples are played.

Analog Filters Yes, the SP1200 has analog filters ! The frequencies can be internally adjusted. Two of the channels the ride/crash and hit hats are unfiltered. Four others (snare/rim, bass, claps. cowbell) are each filtered with a static five pole 1dB Chebyshev filter, set at frequencies to optimise the sounds. The remaining two channels (0 and 1, the toms) each use a dynamic VCF. They use the SSM2044 with a simple AR enevelope generated by the Z80. They create a 5ms sloping attack, followed by a decay. The frequencies can be internally adjusted.

Channel 6 and 7 are unfiltered. The other four channels are each filtered with a static five pole 1dB Chebyshev filter, set at frequencies to optimise the sounds.The filters can be heard on the MIX output all the time, and on the individual outputs if the jack is half inserted.

Internal Mixer The eight voice channels are internally mixed into one, along with the click channel. A TL084 op amp is used.

Diskette Drive The SP1200 has an integral 3.5" DS/DD floppy drive. It enables sampled sounds and sequences to be stored to diskette.

Diagnostics

The debug program is now part of the operating system rather than being a separate EPROM, as on the SP-12. To activate the diagnostic software, power the instrument up while holding down the SETUP button, or press SETUP before a disk is loaded. The SP1200 will cycle through a total of 12 tests, you can turn the SP1200 off at any point.

• CPU RAM test
• ROM test
• Sample RAM test
• Buttons/footswitch
• LCD
• LED's
• Sliders
• Sample Trim
• MIDI
• SMPTE
• Dynamic buttons
• Floppy Disk

There are 7 trimmers on the main circuit board. Four are for the DAC's, one is for the sample offset, and the last two trim are dynamic filters.

Sample Diskettes

E-mu Systems - Original Set The SP1200 was sold with five 3.5" sample diskettes:

• ZD501 Latino Ensemble
• ZD502 Congas
• ZD503 Kyodai Rock
• ZD504 Standard Traps
• ZD505 Orchestral Bash

E-mu Systems - Factory Samples E-mu produced a range of 15 additional sample diskettes for the SP1200. ZD506 - 520 were sold as a set for expanding the SP1200 (part number AD3587-03). There are no longer availabel from E-mu Systems.

• Kid Nepro have a 100 sample Diskette Library for the SP1200 ($800)
• Northstar Samples have a 63 sample Diskette Library for the SP1200 ($20 each)
• SoundsForSamplers have a 20 sample Diskette Library for the SP1200 ($100)

MIDI Sample Dump

The SP1200 can exchange sample information using the MIDI Sample Dump Protocol. Mac programs such as Sound Designer II and Alchemy supported this format, but they are no longer in production. More recent programs such as Wavelab may have problems with the 12-bit format and the specific SDS implemented (MMA).

Repairs

Overview The SP1200 is on the whole a reliable drum machine, with few mechanical parts and a robust electronic design. The main problem areas are the PSU, the LCD and sliders and buttons.

Warning Please only attempt a repair yourself if you are competent at servicing electronics, use a service centre if in doubt. The SP1200 is easily damaged or the case melted by amateur attempts at repair.

LCD Overview The SP1200 uses the same 16x2 character LCD as the Emulator II. This is an Optrex unit with an EL backlight. When new the display is bright blue with grey/black characters. The LCD does fade dramatically over time, and the backlight can fail or the inverter that drives it can fail too.

LCD Age After around 2000 hours use the LCD will need replacement, and its a good idea to replace the LCD whilst parts are still available. You can check when the LCD was manufactured by looking at the code stamped on the back of the LCD in black. The first 2 characters are the year, and the third character is the month.

LCD Viewing Angle The LCD viewing angle can be controlled by varying the voltage on pin 3. The SP1200 has a preset viewing angle controlled by resistors R1 and R2 on the panel PCB. You will not need to change this.

LCD Part Number The original part number is an Optrex DMC16207-AE. This is a 16x2 LCD with EL backlight. The physical size is 84x44mm and it uses a standard single row of 14 data connections. E-mu Systems no longer have any spares, and this is a good job as its expensive from them! The current Optrex part number is DMC16207N-EB, and this LCD is widely available for under $25/£15. Try www.digikey.com.

LCD Inverter The LCD backlight (the blue colour) is driven by a small inverter that generates 100VAC at 400Hz from a 5V supply. The inverter is a NEC (NEL-D32-46), and its a small black plastic box that sits on the front panel PCB to the right of the LCD. The inverter can fail in which case it will need replacing.

LCD Replacement The LCD can be replaced relatively easily but you will have to remove the front panel PCB and desolder/resolder the 14 way data cable and 2 way backlight cable that connect it to the front panel. You may also need to file down the PCB to get the LCD to fit as new LCD's don't have sloping corners. Ensure the new LCD face and the LCD transparent cover in the front casing are both protected whilst your desolder/solder. You may also need to replace the 14 way cable between PCB and LCD, as this is difficult to desolder.

DAC Chip The SP1200 uses an AD7541 12-bit DAC, which is still widely available.

Filter Chips The Emulator SP1200 uses SSM2044 analog filter chips, which occasionally fail and take a voice down. These are hard to locate.

Missing or Damaged Slider Knob The Drumulator has one slider knobs which can be easily lost or damaged. They are available from Farnell (part number 766756).

Missing or Failed Small Push Buttons The Drumulator uses a small momentary push button for most of the controls. After 15+ years use they are beginning to wear out and even with cleaning still don't work immediately. They are easily replaced with new buttons made by E-switch and are available from Digikey in the USA (blue: EG2556-ND, red: EG1325-ND, black: EG1321-ND). A full set of buttons will cost around $50, and you can choose from a range of cap colours to customise your Drumlator. You will need to desolder the old buttons carefully.

Large "Pad" Buttons Replacements can be bought for US$11 from EPR Electronics in the USA. If you find the pads stick, carefully lever the top off and lubricate the pins with a silicon lubricant.

Fuseholder Not quite the same colours! Some models of the SP1200 use a square black external fuse holder, with an internal red lid and fuse. These were made by Littelfuse and are: Low Profile Snap Mount 15A 250V Part Number 348871

Rotary Pots The SP1200 uses three front panel potentiometers which tend to grind a bit after 15 years use. They can either be cleaned or better still replaced by a higher quality 10k Log potentiometer. We use nice Bourns Conductive Plastic models with new knobs.

Power Supply The power supply is getting old by now and failure is not uncommon. One of the rails may go out of specification. Replacement PSU's are not available, so the best option is a service centre repair. It is very easy to service as it is made of discrete parts and its not a linear power supply.