Intro and Transcendent 2000 Slow Oscillator Build

I impulse bought a Behringer 2600 a month or so back after discovering Sam’s Youtube channel and got bitten by the analogue/modular bug.

I can already do digital electronics including PCBs etc so I figured I can learn the analogue stuff and save some £££ in the process.

And the Transcendent 2000 looks like an interesting starting place, given the schematics are easily available. Original magazine articles:

So, here’s my breadboarded slow oscillator. Layout pretty much matches the schematic.

I was going to post schematics and scope traces here but I’m only allowed one image :frowning:
But the period is running from 50ms to 15s which matches the design (0.06 to 20Hz) and the waveforms and peak-to-peak values look correct for the triangle, sine and square waves.

So I’m feeling rather chuffed. I’d appreciate feedback if I’ve made any mistakes.

Connecting it to the 2600 I notice that the outputs need to be buffered, especially at low frequencies.

I figure if I want to make this into a module then I’ll need a couple of enhancements:

  • The square wave outputs need to be buffered.
  • The sine wave output needs to be amplified to 10V (or should that 12V?).
  • And I’m tempted to make the sine output bypassable so I can still use a ‘true’ T2000 value (or would it make more sense to add extra attenuation the VCO input?

And on the input side I’d like to be able to add voltage control. I’m guessing that would be an extra input to IC32 pin 2? I’m watching the Moritz Klein stuff on YouTube and I think he’s covered that in the VCO build using an NPN transistor. I’ll have to research but I’ll happily take guidance on that.

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My first analogue synth was a Jen sx1000 which seems very similar to this. (Are they related?)
I’m tempted to build the whole 2000; keys, knobs and a mono out. Something you can abuse/play without a screen or menu.

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It looks like the Jen was Italian and a year older, so probably no connection.

I’m hoping to move on and do the whole thing but as modules. There’s no reason those couldn’t be combined into one unit though.

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And here’s the Transcendent 2000 noise generator. I’ve rejigged it to use 4015 shift registers instead of the 4006 and moved a couple of components that make more sense in the VCF. Before:


After:

Breadboard:

Sillyscope traces (Ch 1 is the attenuated output to the VCF, Ch 2 is unattenuated one to the S&H):

The clock circuit is running a little slow, 11kHz as opposed to 30kHz claimed in the docs. I wonder if this is caused by the breadboard? I may need to experiment with component values when I get to the PCB stage. Also, I used a 47nF for C44 as I didn’t have a 33nF to hand. I assume that won’t make a significant difference though.

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