Today, for your entertainment, the Elektron Analog Four will shamelessly expose itself. Or rather, I took it apart and snapped naughty, naughty photos, even some thermal pics for good measure.
So anyway, I recently had to take my Access Virus TI keyboard apart for troubleshooting, and in the process I took some tasty thermal images which you can find over at The Virus TI Forums.
The bottom line was that the Virus TI was mostly a clean build, with few bodge wires i.e. they had to manually fix some problems in the PCB layout. Not the cleanest thing, but it usually happens with the initial runs of a new product. Other than that I found that the Virus TI was very well made, even though it did have some minor thermal issues, i.e. some parts are clearly operating rather close to their specification limits and drain power even while the TI is “soft-off”.
When I took apart the Analog Four I was ready for anything: Huge coils, discrete electronics, frankly I was expecting some frankenschematic with huge analog components and only one tiny little chip driving the display and doing the sequencer and stuff. Boy was I wrong.
This is an amazingly well built machine. It’s easily one of the best examples of electronic product engineering I’ve seen. First of all, the upper half comes loose with just 6 screws, and lifts up easily. The connectors are sturdy and won’t come apart on their own, and it’s just two ribbon cables really. The upper half contains the display buttons etc and not much else, so I didn’t bother disassembling that. Also… you know, it’s expensive and I wasn’t really interested to see tons of buttons on a pcb. But one nifty detail…
That’s right, space invaders. Oh and also, extra airvents. Just in case something gets hot, which never happens because this machine is just too cool.
Right then. Off to the main course:
A Spartan 3A FPGA, costs about $9, contains 50000 gates and over 1500 logic cells. This is very likely controlling the analog circuitry, doing stuff like setting parameters and the likes.
There we go: A Coldfire MCF54415 32 bit MCU. 250MHz, 2.1MIPS, 64k internal SRAM, and a ton of other stuff: integrated USB host controller, dual 10/100 ethernet, internal hardware acceleration for various encryption and hashing algorithms, SD card controller, SmartCard controller, various DACs, lots of timers and a ton of programmable IO pins. I’d say it’s safe to say that this is the main processor. And it’s a beast. Too bad about the ethernet support though, would’ve been cool to have the A4 have some sort of internet connectivity… maybe a web based UI? Would be awesome!
Next to that we have a Micron 256 SDRam chip (2WG22) and a Toshiba flash memory chip. My guess is it’s a 2GB chip but I couldn’t find the datasheet to verify.
On the other side we have this…
A 16MBit NVRAM chip from Everspin, based on MRAM (Magnetoresistive random access memory) technology, with a guaranteed data validity for > 20 Years. This is about as good of a long-term storage as you can get, beats the hell out of the usual battery-backup solutions you find in classic synths. Oh and right next to that is ANOTHER flash memory, this time a 64MBit chip (M29W640FB) from STMicroelectronics.
This is the largest part on the board. A giant ferrite coil from Coiltronics. Most likely not used for synthesis but for internal power regulation, a theory that’s further solidified by the presence of a LT3579 DC/DC converter and a few diodes. Also these parts are on the opposite side of the board, as far away from the analog sound circuitry as possible. Which brings me to…
HC373 is a D-type latch, there’s some additional logic circuitry there, nothing to write home about. Hmm, where’s the analog stuff?
Aha, Coolaudio V2164M Voltage controlled amplifier (2 per voice), T084 opamps, L339 Comparator, couldn’t find anything about the HJ4051. Your guess is as good as mine. Also on the board is one single Cirrus Logic CS42436 6-in 6-out ADC/DAC.
So yeah, not a lot of exciting stuff. The four voices are clearly visible on the PCB, but it’s difficult to make out the oscillator/filter/LFO sections. There’s a ton of opamps however, as well as lots of little caps that may well be part of oscillator sections. The thing looks absolutely beautiful but there’s not much to see, sadly.
But what about the thermograph? Maybe we can see something interesting going on there? Well…
This machine is cool. Too cool for IR photos. In fact you can hardly make out that I was playing with it just moments before. This is in contrast to my Virus TI…
But anyway, open up the A4 again and…
Nope. Nothing that gets warm really. Except for the DC/DC converter coil…
…and the power supply:
Now this is the Virus TI in comparison:
So there you have it. A peculiar, beautiful device. The analog circuitry is mystifying. Where and how it interconnects with DAC/ADCs and the digital world seems to be quite a complicated matter. My guess is that there’s analog oscillator/filter stuff going on at first, controlled by digital glue logic. The audio signal is apparently then sent through an ADC, the effect processing being done digitally, after which the four channels are converted back to analog for output. At least, that’s my guess. Maybe someone can correct me there and shed some more light on it.
There’s lots of different memory chips in there, including an innovative long-term storage for your kits and patterns. In terms of built quality, Elektron ranks up there with the very best, worlds apart from mediocre-quality stuff like the Kronos.
I can only conclude that the guys at Elektron are not only competent, but they also really enjoy what they’re doing.
P.S.: Give us a bigger display next time. Maybe an OLED screen? Oh and… pads for the sequencer buttons would be nice. Perhaps even with force detection. And it should whiten our teeth while we sleep. Thanks 
