Tag Archives: Oberheim DMX

Kawai K3 for Akai S900

I just swapped my Kawai K3 for an Akai S900 and a pile of cash. The K3 was one of those synths that are nice, but of some reason never is used. For that reason I decided to sell it.

I’ve also been working on converting Fairlight I/II/IIx disks to other formats. Akai S900 is one of them. So far I’ve used one of my Oberheim DPX-1s to playback the disks, but a lot of the S900 file formats aren’t fully documented. To be able to reverse engineer those formats I needed a real S900 to be able to set parameters. The DPX-1 is a sample player only, no parameter can be changed.

What’s interesting about the S900 and S950 is the fact that they have variable sample rates just like old drum machines like DX/DMX and Linn. This means that the S900  can play back sounds at any speed between 7.5 kHz to 40 kHz, and it does this by changing the clock. This could be described as manually turning a vinyl disk at different speeds. Most newer samplers uses the “drop sample” method instead. What this actually does is to throw away or duplicate samples. If a sound is to be played back at the double speed using the drop sample method, every second sample is discarded and never played back.

Next thing is to temporarily take the HxC SD Floppy Emulator from the Roland S-330 and put it in the S900 for testing my own generated disk images.

How the hihat in SCI Drumtraks works!

I just wanted to share how the SCI Drumtraks creates the closed hihat (ch) sound from the sample that is actually an open hihat (oh).

The hihat chip in the Drumtraks is a single 2764 containing a whopping 8 kb of samples.  Remember that electronics where much more expensive back then, and costs must be cut. One method was to use the same sample for the oh and cc. This was the case on the Linn LM-1, Oberheim DMX / DX,  Drumtraks and probably a lot of other digital drum machines from this era.

The trick is to use the last part of the oh sample and add some envelopes to it. Below is the Drumtraks hihat chip loaded in Adobe Audition.

The red marker marks sample 4096, which is exactly half of the total 8192 samples. It's approximately here the ch starts.

The red marker marks sample number 4096, which is exactly half of the total 8192 samples. It’s approximately here the ch starts. But, when recording the ch, it doesn’t look exactly like that. Take a look at the recorded audio below:

This is the ch recorded, as you can see an envelope is added by the Drumtraks to fade it out.

To make the ch fade out quickly, an envelope is added by the Drumtraks.  If you don’t believe me, compare this image to the first one, the peaks are easy to identify.

What about the oh, does it only play until sample 4096? The answer is no, the oh plays the whole 8192 bytes. Take a look at the screenshot below:

First part is the oh recorded from the Drumtraks. Last part is the data from the chip. As you can see, they are 'identical'.

The first part is the oh recorded from the Drumtraks. Last part is the data from the chip. As you can see, they are ‘identical’. This means that when the oh is played back from the Drumtraks, the whole sample is used.

Notice how different it sounds when processed by the Drumtraks, and that’s the reason for having a Drumtraks. 🙂

Just An Illusion, Oberheim DMX + Yamaha TX81Z

A quick test playing the bass line from Just An Illusion on the Yamaha TX81Z. On the original recording the bass is from a Roland SH-1000, played manually without any sequencer at all. I noticed that the Lately bass was quite similar even though it’s an FM-synth. I especially like the “rubber” touch of the sound. Since the original was done without sequencing, I decided to do that as well. And it’s actually very hard, I’m impressed by Tony Swain’s tightness. The velocity controls the filter on Lately Bass, so it’s important no too hit the keys to soft or hard.

The drumbeat on this recording is from the Oberheim DMX, I don’t know what’s used on the original record. You might recognize the DMX sound from Into The Groove, especially with the reverb on the clap.

Effects used:
Lately Bass = Logic standard chorus plug, a bit of eq
DMX Clap = Logic Gold Verb
Everything else is vanilla. Recorded on three channels through the preamps on an RME Fireface 800.

Note that I used the Facetime cam on my MacBook to record this since couldn’t find the tripod for my Canon DSLR. Unfortunately, Photo Booth records with variable frame rate, which makes the audio/video sync unstable, especially noticeable in the last clip.

Oberheim DMX Midi upgrade arrived (unboxing)

Today the Midi upgrade for the Oberheim DMX and some other stuff arrived from Electrongate. Check out the unboxing pictures with descriptions of the contents!

Oberheim DMX parts ordered from Electrongate

I’ve just ordered some stuff from Paul at Electrongate. He’s been very friendly and helpful during our e-mail correspondence.

Here’s a list of stuff that I ordered;

  1. DMX Midi Upgrade with a custom made breakout box, more details to come
  2. Thumbscrews for the lid, those were missing
  3. A new NiCd battery that will be relocated in another position than the original one
  4. A couple of rare Molex connectors that the DMX has on it’s back for CV and trigger
Oberheim eagerly awaiting it's MIDI upgrade to arrive.
Oberheim eagerly awaiting it’s MIDI upgrade to arrive.

Oberheim DMX bargain

Just bought an Oberheim DMX. It was a real bargain, listed at 2000 Danish crowns ($350). I called him and offered him 2500 ($440) if he’d reserve it for me. He had one person that had contacted him before that wanted to buy it, and said he would call me if that person didn’t buy the DMX. At that point I told myself that it most certainly would be sold.

Later that day he called me and said that the buyer didn’t have the cash. So now I was first in line. I jumped in my car and drove to Denmark. Even if the condition wouldn’t be great, or if a voice card would be bad, it would still be a bargain. When I arrived and saw it in real life I couldn’t believe my eyes – it looked mint and worked flawlessly. I bought it for 2500. He told me that people after me in line had offered him 3000 ($530) and more. Very nice seller by the way! He told me that it’s this DMX that is used on this recording. I think the seller is the guy playing the bass in the video.

On the way back I turned on the radio and heard Into the Groove by Madonna. That must have been a sign. Just like when I heard Carrie by Europe when I was driving home with my JX-8P.

The sound is fantastic, very punchy. And extremely present! Already love it!
Now I have to stop writing and Google for MIDI-mods and check if the battery could cause problems.