Vermona ER 9 Drumexpander

http://www.bleeps-and-peeps.com

Owners Manual: vermona er9 ownersmanual.pdf

Schematics: vermona er9 schematics.pdf
Midi-Interface: stereoping

Technische Daten & Full Description: http://vermona.de

Analoges Preset Rhythmusgerät mit 16 Rythmenschaltern, 9 Instrumente mit je einem Lautstärkeregler ( bass-drum, tom-tom, bongo, claves, snare-drum, cymbal, high-hat, cow-bell, maracas ), 1 Gesamtlautstärkeregler, 1 Temporegler, 1 Startschalter, 2 Taktlampen, 1 Ausgang als Diodenbuchse Die Rhythmen: march, fox, shuffle, bossa nova, rumba, beguine, samba, cha cha, tango, rock, beat 1, beat 2, slow beat, slow rock, waltz, slow waltz

Mehr Soundsamples in der Rubrik Love the Machines März 2003 der Zeitschrift Keyboards

Das Gerät gab es auch als Einbauvariante in diversen Vermonaorgeln mit 6 Instrumenten ( ET-3 MR )

und mit 9 Instrumenten in der ET 6-2R, Selecta, Formation 3 und Formation 3MR

Noch mehr Bilder und Infos von der ER9 von Rainer Nickel´s Drumcomputerpage





Controls:

• Sounds: Bass Drum, TomTom, Bongo, Claves, Snare Drum, Cymbal, High Hat, Cow Bell, Maracas
• Separate Volume Regler für alle Sounds
• Summe Volume (Lautstärke Gesamtausgang)
• Temporegler
• Start/Stop Taste (Grün)
• Gesamtausgang als Din 5polig
• Die Presets: March, Fox Shuffle, Bossa Nova, Rumba, Beguine, Samba, Cha Cha, Tango, Rock, Beat I, Beat II, Slow Beat, Slow Rock, Waltz, Slow Waltz

first example:

second example:

Vermona ER-9 Midiinterface: http://stereoping.com

The Vermona ER-9 - a little overview

The ER-9 was built by Vermona from East(!)-Germany aka DDR in the early 1980ies (or even late 1970ies?). It has 16 Rhythms which can be mixed by pressing multiple Switches and 9 Instruments: Bassdrum, Tom, Bongo, Claves, Cowbell, Snare, Cymbal, Highhat and Maracas. The first 6 Instruments are built with a double-T-Matrix, mostly around just ONE transistor. All voices are mixed into a 2-transistor-mixer. Extremely clean, simple and efficient. Don't beleive everything they tell you about DDR-products, they made some cool and highquality things, e.g. the worlds first regridgerator without FCKW. This drumcomputer is about 40 years old and still works perfectly. And i just love it's design.

Inside there are multiple cards which are stuck into simple sockets. Most cards are housing 2 or 3 voices. On top of the cards are trimpots for calibration. On most cards one is for calibrating oscillation-point in the doubleT-Network or simply spoken: decay for BD, Tom, Bongo, Clave or Cowbell, which has 3 Oscillators, most analog drumcomputers including 808 just have 2 for the cowbell. If you stumble upon a ER-9 and the owner sais "it just makes a constant tone when i plug it on" i guess it is just a decalibrated pot letting one voice selfoscillate.

Some patterns of the Vermona ER9 via midi from fruityLoops

Midiinterface

Now on to the midiinterface around a Atmega8. The code is based on Vacolocos Opensource Triggerinterface. I just copied the scheme from it's internal diodematrix and connected the Controllerpins to the Triggerpoints on the sockets of the voicecards. The interface is fixed listening on channel 9 (naturally, i mean it's name is ER-9), i was to lazy to program and hole-drill a 'learn'-switch and a LED. The triggerlength is modulated by midivelocity. Some voices benefit from this (BD, SD) and can be played with velocity. The other voices have a such defined trigger-edge that even the slightest modulation of the triggerlength resulted in 'sound' or (nearly) 'no sound', but it's ok, you can't have everything.

On comparing the sound of the individual voices between internal triggering and the 'normal' miditriggering with the copied trigger-scheme through really big speakers i noticed a slight difference in sound. Some internal triggered sounds (when i remember right Tom, Bongo, Clave and Cowbell) had an additional highfrequent peak at the beginning. I guess my triggersignals were to weak (5 Volt) so i had to boost them up to 12 Volt. After that the sounds were perfect identical. Scheme for boosted is to the right. I only made that for voices which needed them. At least the Hihats just didnt want to play by the miditriggers although its nearly identical to the cymbal which works fine. I just skipped the onboard diode, then it worked.

Maracas is special. They are not triggered like the others. Maracas gets a longer clocksignal causing a repeating voltageliftup at the base of a transistor. This causes the transistor to amplify a noisesignal, also lying at it's base. That means, as long as it has high voltage, the transistor is amplyfying and you hear the noise. The lift and drop of this base-voltage is dampened by a capacitor for making attack and decay long. The amplyfied noise is filtered before going into the mixer. The triggerpulse for this had to be much longer and isnt shaped through a capacitor. It goes through a pot directly to the board between r25 and r26.

Several modifications

Stangely my machine had a very low outputlevel resulting in extremely bad signal-noise-ratio. After several hours of unsuccessful errorsearching and replacing capacitors in audiopath and powersupply, i just put a 1M-pot instead of the default 68k-resistor in the feedbackpath of the output amp. Now it's much better.

Another useful modification was to shortcut the internal clock. Even when no internal pattern is selected the clock runs and you can hear very lowlevel triggernoise and even some voices (mainly cowbell) ring a bit. Normally you wont hear them when the frontswitch is not pressed. The frontswitch of the vermona has 2 tasks: 1. reset the counter of the clock which triggers the voices through the diodematrix. 2. to lift the voices sum-point up in voltage to mute the output. But i want the output tho be always open otherwize the miditriggered voices wont be heard. So i removed the cables from the switch and attached the 2 cables from the shortcut clock instead. The result is, the output is never muted, when switch is released there is no triggernoise any more and when switch is pressed i can use the internal patterns when i want it to accompany my freestyle-playing (without midi).