Tuesday, December 16, 2014

Moog Sub 37 Tribute Edition Sounds



Sub 37 Tribute Edition Moog Synthesizer. I am smitten. Basses, arpeggios, and some FX weirdness. No external effects applied to the synth sound, just a backing track by the trusty Volca Beats.

Sunday, October 26, 2014

Burning EPROMs for Old Drum Machines in Windows XP

Many old drum machines like the Sequential Drumtraks, Oberheim, E-mu and Linn use sound that is stored digitally on microchips called EPROMs. It is possible to change the sounds by swapping out the factory EPROMs with ones that have our own custom data burned into them.


WHAT ARE EPROMS?
EPROM is an acronym that stands for Erasable Programmable Read Only Memory. We can write memory onto these chips using a programmer only if erased properly. EPROMs are re-usable devices, where ROMs are not.

DEVICES I USE FOR BURNING EPROMs
1) I make use of an older Windows XP desktop computer with a serial connection cable. Back in ye olden days dot-matrix printers were connected to the computer using the serial cable.

2) To erase the EPROMs I use an ultraviolet light erase machine with a timer that is easily available on ebay for $10 or $20.

3) I also use an old Willem Programmer from ebay for around $30 or $40. The programmer should come with a software disc, if not just go to their website and download the needed drivers.

4) A 12 volt DC power adapter like those from radio shack. You can also find used power adapters for really cheap at common thrift stores.

DATA FORMAT
You can find many files you need on the internet. I use .bin files, which stands for binary. As long as the .bin files contain the appropriate sample data or operating instructions for your objective there should be no problem. Make sure the memory size of the chip matches the device it will be installed. I'm burning a 32kb chip today for an MMT-8, so I'll be using a 2732 EPROM where 27xx is the type of EPROM and xx32 is the memory size of the chip.

HANDLING SENSITIVE ELECTRONIC DEVICES
The programmer and the EPROM chips are sensitive to electro-static charges. Ground yourself by touching something metal to ground like a sink faucet to dissipate static charges that build up in your body to prevent damage to the devices. I also wear an anti-static strap that draws out static charges in my body and dissipates them safely.

CONNECTING THE PROGRAMMER
Connect the 12 volt power adapter to the programmer and make sure the lights come on. Connect the serial line cable to the computer and the programmer. USB cables only provide 5 volts of power so I do not use it for this purpose. Before I can burn the EPROM I need to make sure the EPROM chip is completely erased, then resolve a couple of nagging issues with Windows XP.

ERASING EPROMs
Erasing EPROMs is simple. First make sure the clear window on the EPROM is clean. When you look down through the window of the chip you will be able to see the actual microchip inside. Then put the EPROMs into the drawer, close it and set the time for 5 to 10 minutes. The UV eraser uses ultraviolet light that will nullify data residing on the chip. As a safety note do NOT stare directly into the ultraviolet light, it can have serious consequences to your eyes.

WORKAROUNDS IN WINDOWS XP
You may encounter input/output errors when trying to use the programmer the first time. To burn EPROMs we want the software to have instant and direct access to the programmer but Windows does not allow this. As a workaround we will need a little application called userport, do not worry - it is safe to use because this little app is recommended from the Willem Programmer website. I open the userport program and 'add' addresses 0-378 to be direct control enabled. I am not sure the exact address the serial connection will be using, but enabling a whole set of addresses will ensure things will go smoothly. I leave the userport application running in the background. When I am ready to start the Willem Programmer Application, I right-click its program icon and set compatibility mode to 'Windows 98'.



SETTING UP THE PROGRAMMER
The programmer I am using can host a large variety of microchip devices. Which EPROM I am actually using will require that I make the proper jumper settings to the programmer. Jumpers are simply a set of small bar contacts that slide over small pins to create electrical connections. In this way we can change the circuitry to fit our needs for different situations. Do not sweat this, because the programmer application will actually show you which jumper settings to use once you have selected the appropriate chip from the menu. Next you need to set the DIP switch to match what the program shows. The program also shows you the correct position of the chip in the programmer. Take special note of the correct position of chip PIN #1 which is indicated by either a notch on the top edge of the chip or a small dot next to the pin itself.




CHECK THE EPROM IS BLANK
Install the EPROM chip in the programmer and, using the computer software, do a 'Blank Check' to see that it has been completely erased. Even if one single data location does not return a null value you will receive a 'Device Not Empty' message and will need to put the chip back in the ultraviolet light eraser.



AT LONG LAST, CAN WE BURN THE CHIP ALREADY?!
At this point the userport app should be running in the background and have the direct control still enabled. Using the computer software that came with the programmer, browse to find the .bin file to load its data into the buffer, and burn the chip. Once you have burned the data, you will need to verify the data. If anything unusual happens, the application will tell you, and you will have to erase the chip again and start over. Or try a different chip if you have erased more than one at the same time. When you are satisfied the chip has been burned properly, put a piece of acid free tape over the clear window to prevent accidental data corruption. Once finished go back to userport, select the addresses specified earlier, and click the 'Stop' button to deactivate direct control. Then exit the application.





This process is what works for me. You may or may not have the same experience or face the same issues. But hopefully this will give some insight into how burning EPROMs could be done and what issues you might face. Hopefully newer EPROM programmer designs have resolved some of these issues. Happy programming.

Sunday, August 17, 2014

Yamaha TX81Z FM Synth Sounds Demo 2


The patches can be downloaded on my download page

Continuing sonic explorations of TWO TX81Z FM Synthesizer Tone Generators this time. Each unit chained for even/odd notes: one panned slightly left and the other to the right. Sounds are outrageous in the dry state but can be made completely preposterous with the Big Sky reverb.

Here's a rundown of the sounds:
0:09 Cymbiosis - Synth pad with cymbal harmonics.
0:38 Ritual - dark tribal bass. Add huge reverb to this one.
0:53 Darknights - Smooth filtered sawtooth with swell.
1:16 Heavyw8 - Super fat bass. Start your own earthquake.
1:33 Wowabass - It literally says wow.
1:44 Drum kit bass drum, snare, tabla, hats
2:34 Sawtopia - Smooth sawtooth pad w/ organ swell.
3:10 Saw Bass - Bread and butter bass.
3:19 Fortress - Super dark cello w/ vibrato.
3:51 Transistor - Hot pad inspired by the Novachord, transistor hum
4:20 Sync Bass - The way FM can bass
4:31 SmakMyBass - Prodigy Fat of the Land Bass on steroids.

Wednesday, August 13, 2014

Exploring The SH-101 Plug-Out Roland Aira System-1


The focus of this demo is the SH-101 plug-out: down-n-dirty short basses, basic arpeggios, and sequences from Arturia Beatstep. I don't have an original SH-101 so I can't comment on how similar it may be. I stayed away from tone/crusher and kept the delay/reverb to a minimum just so you could hear the SH-101 sound engine in all its monophonic glory. Some backing rhythms provided by SCI Drumtraks and Roland MC-303.

Sunday, July 13, 2014

8 Minutes with an Akai AX-80


There are quite a few good demos of the AX-80 out there already. I wanted to program a few basic sounds and some unique aspects of the AX-80. Some parts I use the Beatstep sequencer, chord memory, and the Big Sky reverb.

Saturday, July 12, 2014

5 Minutes with a System-1


Quick demo of some sounds made on the Roland Aira System-1 Synthesizer.

Saturday, June 14, 2014

5 MINUTES WITH A KORG POLY-61


5 minutes of your time listening to the Korg Poly-61 6-voice hybrid analog/digital synthesizer. Paid $50 for this hot mess because it was absolutely BRICKED. As you hear some functions working again but it is still fussy as you see at the end of the clip. Sequential Drumtraks and Strymon Big Sky also featured.

Friday, June 6, 2014

Korg Poly-61 Key Contact Repair

Key contacts are the source of much headache on the Poly-61.  Much has been blogged and posted by others about dis-assembly of the keybed, membranes, and maintaining clean key contacts.  However in the case of THIS machine no amount of cleaning could bring back key functionality.  I believe this is due to the membranes simply wearing out and the gold contacts losing much of their conductance.  Replacement membranes are very expensive, and I wanted to explore cost-effective methods to milk the last bit-of-life from this keybed.

This repair involves re-coating the membrane contacts with a conductive pen, adding plastic shims to the keys, and replacing broken key bushings that have allowed the keys to sway too much side-to-side.  The biggest disadvantage to this repair is a small number of keys are STILL un-responsive.  Furthermore, re-coating the contacts in this manner will produce an effect known as bouncing.  Bouncing is when a key is pressed it may send two, or several, note-on signals in rapid fire succession.  This is because the contact, on its way to being fully depressed, will bounce several times on-and-off before settling.  To me I can live with this more than have a dead keybed that does nothing.  Anyway...on with the repair process.
Using a CircuitWriter pen from radioshack I coated the membrane contacts twice, with 4 hours between coats. I allowed the contacts to cure overnight. 
Using the pen takes finesse. Shake vigorously for at least 2 minutes after the little ball becomes free. Practice on something else first. Press until flow starts for two seconds, then swirl in circular motion to cover surface of contact.  Here's what the covered contacts now look like. Next to add plastic to the bottom of the keys. After experimentation, I found a 1mm thick plastic was required, cut to 8mm x 10mm rectangles. I searched far and wide, and found an Artists Loft brand graph ruler from Michael's was perfect material. Tricky to cut with an exacto knife, but can be scored and bent to finish the cuts. This photo shows the rectangle in place on one of the keys. To tape it in place I used good old fashioned duct tape, the perfect redneck engineering solution. Replace and test the key. Another piece of tape was sometimes necessary. I found three layers of tape to cause errant self-triggering of the key. Next I replaced some damaged key bushings. First, you guessed it, I used duct tape to build up a base layer on the bushing prong. In this photo you also see a bare prong, a good bushing, and another damaged bushing. Then I cut a small piece of 3/16" Heat Shrink Tubing to place over the prong. This photo shows the heat shrink tubing in place. I found the tubing fit snugly without any heat being necessary. It's not a perfect replacement for an actual bushing, but it greatly improved the keys swaying side-to-side. And that's it.

Thursday, May 1, 2014

16-Step MIDI Filter Sequencer

The designs for the Step Control Sequencer are at
https://www.dropbox.com/s/2qrzs54olngtqqz/StepSequencer%20R1_0%2005-02-2014.zip

Following two months developing code and playing with breadboards I present this quick demo of the recently completed DIY digital 16-step control sequencer. This sequencer was designed for controlling filter steps on an MS-20 mini. The sequencer puts out variable step control voltages up to +5 volts and synchronizes to midi start/stop/clock messages. To achieve control over 16-steps with only 8 pots, I employed a toggle switch that can program steps 1-8 or steps 9-16 without reading changes until the pot positions are changed. All the control processing happens on the Arduino Mega. I have prototyped two circuit boards for this project. The first is a midi shield. The midi shield features one minijack control voltage output, one midi input with an opto-isolator, and one midi thru port. The second board I made is a panel control used for the pots and LEDs. The Arturia Beatstep is the master clock and is sending midi note data to the MS-20 at the same time the step-sequencer is controlling the filter with control voltages. The Sequential Drumtraks is put in slave mode for this demo.

Friday, April 4, 2014

Superfalling

Here's a little thing I whipped out using a Matrix-6 and some reverb.