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Sunday, July 18, 2010

It's Alive!

Thank you Nyle Steiner! (The top blurry cell phone photo is Nyle in front of his workbench.) I stuffed the newest VCO prototype and it basically worked first time. I was using a wrong value for a trim pot which prevented the triangle wave output buffer opamp from working, but I got that figured out and it works great! Here are some more crappy cellphone photos of the screen of a DSO Nano O'scope (long story but I loaned my bench scope to Nyle for a couple of weeks). The photos don't do justice to the screen of the Nano. Very cool little scope. I think this is the first new Steiner Synthesizer Company VCO in 30 years give or take. The pulse and sine outputs are higher than the triangle and saw outputs, so I'm going to triple check all the component values to make sure I'm doing this right. I'm also a little lost regarding the adjustment of the min/max width trim pots for the pulse wave. It's another question to ask Nyle.

Now, on to the sequencer prototype. I'm way excited again about this whole thing.

I've also got the rack/power distribution system figured out. I got the new power plugs and they fit perfectly in the existing cutout. I drilled the holes for the mounting screws and they look and work great. I don't know if anyone but Nyle and I will use the rack system, but it sure looks nice and I think will work as good as they look.

Another odd note. I decided to use adjustable regulators for the power section so I could get an accurate voltage on each board. I discovered through some kind help on the SDIY list I have to have a minimum current draw to effect regulation. I'm going to have to add some small load on each regulator because some of the circuits may not meet the worst case current draw to establish regulation, particularly on the -10 volt side. So another task before the next round of PCBs is ordered. Hopefully though, the next batch will be the first production boards.


  1. 18 trimmers on one VCO board ?! (okay, minus one for the regulator, I suppose)
    I really hope that's only for the prototype boards ?

    And what about that nasty-looking spike in the triangle ?

    Other than these somewhat-negative comments, I'm looking forward to the progress you're making... This sure is a fascinating project.

  2. Hi guy D2. I appreciate any comments/questions.

    The single turn trim pots visible on the edge of the board are there in place of the panel pots. This board has no on board regulation, so no trimmers for the voltage. I did it that way to make it a little more compact and easier to deal with while I was testing it. I thought it was better than hanging a bunch of pots off the board with flying wires.

    That said, in the final board there are still 10 trimmers:

    Min pulse width
    Max pulse width
    Phase sync trim
    DC offset for the sine output
    Sine shape
    Sine shape bias
    Triangle shape
    Volt/octave trim
    DC offset for the saw output
    DC offset for the triangle output

    There are two more which were not part of the original design, but added for the power regulation:

    +12 volt adjust (only if running on +15 volt supply)
    -10 volt adjust (only if running on -12 or -15 volt supply.

    This makes 12 trimmers on the PCB.

    The "nasty" spike on the triangle is an artifact present in many analogue VCOs. While it is visually disturbing, the frequency content of the spike is typically not audible. There is also a peak in the leading edge of the pulse, and the beginning of the sawtooth ramp is not perfectly flat.

    Regardless, I can only conclude since this is a faithful recreation of the original design, these anomalies were likely present in the original VCOs, too. So, I'm not going to do anything more to correct them. I want this VCO to be just like the original including any artifacts which may be in there. I figure they help give the Steiner VCO some of its character and timbre so I'm not going to tweak the design.

    Thanks for your interest Guy D2!

  3. Hi there,

    In retrospect, my comment might have been too harsh. Sorry for that.

    In fact, I came back here because I was just working on a joystick project, using trimmers for pots, so it suddenly dawned on me "hey, that's probably what's happening at Analogue Realities as well..." :-)

    Those 10 remaining trimmers seem okay, yes. Actually, some of them are nice to have.

    Ken Stone's VCO has a bit of a spike too in the triangle. I know it's nothing to worry about, but this one looked a bit too much. But as you say, remaining faithful to the original is of more importance here.

    Can't wait until you're advanced to the stage where us too can get our hands on the unique Steiner system...
    Keep up the good work !

  4. Thanks Guy D2. I honestly appreciate comments, questions, and suggestions. I didn't think what you said was too harsh, just honest questions and comments.

    Please don't hesitate to ask or comment on what I'm doing.