I'm looking at an old fax*: May 7th, 1993 ODR-S Approval. Yes... that's a while ago.
* For the younger ones among you: Fax is like Whatsapp - only on paper.
So it's 1993 and I'm working in the development department at Nobels. Shortly after we brought the first four effects units (Overdrive, Distortion, Preamp, AB Switcher) onto the market in March 1993, the next units followed. Here I tell you something about the Overdrive Special ODR-S.
Basically, the ODR-S in the overdrive section is pretty much based on the circuit of the ODR-1. Here I am going to describe some details about the development of this special overdrive.
The picture on the right shows an ODR-S from 1993. The built-in PCB has start revision 4. The heavily yellowed buttons are clearly visible. In the later series, a better color was used that was significantly less discolored. This is how you can find out the Vintage ODR-S these days!
The battery cover is not original here - it comes from a later production. The first U-shaped battery covers were only pushed on and could easily be lost. And then they did ...
So in the beginning we were able to send many as spare parts. To protect against this work, the new battery cover with a snap-in hinge was developed by Bernhard. And without changing the metal housing! Anyone could snap that into place!
And since that was much more practical, I immediately swapped it on my ODR-S model. I was only interested in electronics. Because that's what matters - right?
The date (c) 1993 is also written on the base plate. On newer ODR-S, the imprint was then (c) 1993-1995. Who can still recognize it: Below is my date coding for the creation of the print file in the form YYMMDD.
But even in these devices there is partly the PCB Rev4. Then at some point the update to the PCB Rev5 came. The only difference is the slightly corrected layout - the values were the same.
Functionality
Input
As in the article Development of the ODR-1, the ODR-S effect pedal basically has the same structure up to the overdrive section 2. From here on there are the bigger differences to the ODR-1.
Blockdiagram
Overdrive Section 1 - Silicon DiodesTwo diodes in the feedback path - also known as "soft-clipping" - are typical for classic overdrives.
Overdrive Section 2 - Germanium DiodesInstead of the two silicon diodes of the ODR-1 after the opamp - also known as "hard-clipping" - there are two special germanium diodes. Unfortunately, these have not been manufactured for a very long time. A 1N60P was therefore installed in later versions. It has a higher forward voltage, so it has a different characteristic which changes the sound. That is probably one reason why the ODR-S from the first series (dark green, 1993) currently achieve a much higher sales price on the 2nd hand market than the newer ones (silver or black housing). |
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3 Band EQInstead of the special spectrum control of the ODR-1, a more complex 3 band EQ section (Lo, Mid, Hi) should follow. For the bass and treble control I used a standard Baxandall circuit, which we* "musicially" adapted in terms of the frequencies. In addition, there was also the mid control in the form of a gyrator. The 2nd frequency response diagram shows how the mid control works. If you turn it to the left, the mid-range is drawn from the signal in a broadband manner; when you turn it to the right, the signal becomes narrower again up to the ~800 Hz mid-peak. *we: That was Jürgen S. at the time, as well as the No1 Music Center team from Hamburg at the time. |
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Here are the frequency response of the Lo and Hi controls (ODR-S 1995 Rev4).
Incidentally, the slight ripple in the bass range comes from the overdrive effect that is already starting to occur!
And the Mid control:
Output-Filter
The output filter was adapted accordingly for the ODR-S and therefore differs from the design of the ODR-1.
Ultimately, it adjusts the frequencies and provides enough output signal!
Conclusion
The ODR-S overdrive pedal is quite versatile with its 3 tone controls. It has a more drive than an ODR-1. The sound sounds nicely rounded, but depending on the setting of the controls, it can also get snappy.
In the past, various ODR-S were rehoused by "Analogman"! This means that the electronics have been rebuilt in a new housing and converted to true bypass. That's how I would do it nowadays...
Interesting video about the Nobels ODR-S: