CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

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rumblesan
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CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by rumblesan » Mon Jan 11, 2021 10:51 am

Hey all,

have recently "finished" my BOG and VV3 panels and whilst everything is pretty much working, I'm just sorting out some of the last bugs and issues (there's going to be quite a few questions I suspect).

I've got the DUSG in my build working, and I'm really appreciating how great it is, but I'm a bit confused by the direction of the controls, and despite following the wiring diagram and checking the schematic it feels like the CV attenuverter is reversed with respect to the Rise/Fall controls. Really I just want to make sure that it's working as expected and there's not some deeper issue.

Turning the rise and fall controls clockwise increases the time it takes for the voltage to change.
Putting a positive voltage into the VC jack and turning the control clockwise "decreases" the time it takes.
Is this standard and I just need to get used to it? or have I gotten something backwards?

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Re: CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by Navs » Mon Jan 11, 2021 12:02 pm

It's not the way it works on my CGS/Bananaloge/Serge VCS, but if the reverse setting gets you the opposite all should be well:

On the VCS, turning the CV pot counter clockwise applies negative CV/feedback, i.e. a linear envelope is made exponential and gets shorter. Turning the knob CW applies positive feedback for a longer, logarithmic response.

So, if you turn the CV knob anti-clockwise, starting from 12 o'clock, does the envelope (or LFO if cycling) get slower?

If that's not it, Ken Stone originally included a form of time compensation in his design. Maybe it's that?
Last edited by Navs on Mon Jan 11, 2021 5:02 pm, edited 1 time in total.


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Re: CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by cygmu » Mon Jan 11, 2021 12:17 pm

Your description matches how it works if you follow Ken Stone's wiring diagram, so I think you have wired it as intended. However it does seem a bit counterintiutive that "clockwise = slower" on the rise/fall knob but "clockwise = faster" on the VC knob.

To get it to work in a more inuitive fashion, you can just switch the wiring of the rise and fall pots: swap the wires to the outer lugs on those two (four, on a dual, I guess) pots. Leave the VC attenuator pots as they are.

People say that "clockwise = slower i.e. greater time" was the standard Serge knob setup, but the Serge kit instructions reproduced at
http://serge.synth.net/documents/kit/dusg.html
clearly refer to clockwise meaning faster e.g.
apply a control voltage from a keyboard, Stopped Function, or Stapped Random Voltage Generator. Turn the RISE and FALL knobs all the way up (clockwise, and apply the output to the control input of an oscillator. The signal should be the same as the input. As the RISE and FALL knobs are turned down, there should be a portamento or slowing Effect on the changing stepped voltage.
[weird typos copied direct from the page... I guess bad OCR?]
...
so I think the wiring that Ken drew was just an error. The wiring diagram in the kit instructions is also the other way around from Ken's schematic, but you need to trace out the original PCB to see that.

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Re: CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by rumblesan » Mon Jan 11, 2021 1:48 pm

thank you both for the clarification. I've got it oscillating, pulse dividing and all the other tricks, so it does just seem to be the wiring reversed.
I was trying to find info on what the controls "should" be but couldn't actually find anything anywhere so thankyou for the pointer to serge.synth.net.

Switching pot wires is easy enough, and I can just do it when I fix the other wiring issues I've got.

interestingly, my wiring is correct according to the most recent elby guide as well (https://www.elby-designs.com/webtek/cgs ... -build.pdf) so I guess that's just continuing the mistake from the original wiring diagram?

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Re: CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by cygmu » Mon Jan 11, 2021 2:56 pm

rumblesan wrote:
Mon Jan 11, 2021 1:48 pm
interestingly, my wiring is correct according to the most recent elby guide as well (https://www.elby-designs.com/webtek/cgs ... -build.pdf) so I guess that's just continuing the mistake from the original wiring diagram?
I would assume that is what happened. It's hard to tell what's going on in that diagram but you can clearly see that it does not match the original Serge wiring: in the Serge kit instructions the clockwise ends of all the pots are wired together and go to pad "U" (which happens to be 0V but you have to trust me on that!) On the Elby (and Ken Stone) wiring diagrams, the clockwise ends of the pots go to two different destinations. So somebody changed something some time... It doesn't really matter but I find it easier to operate the module when clockwise means the same thing on all the controls.

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Re: CGS 514 DUSG controls rise/fall CV attenuator reversed? or maybe not?

Post by wackelpeter » Tue Jan 12, 2021 10:42 am

cygmu wrote:
Mon Jan 11, 2021 2:56 pm
It doesn't really matter but I find it easier to operate the module when clockwise means the same thing on all the controls.
With the DUSg or VCS this can become a challenge due to it's multi-funtionality... turning the rate know to faster would mean faster slopes but less slew, less filtering, less division, etc. ;) but as it's most common use i think is a voltage controlled slope then i think it makes sense to have the knobs acting like on a normal LFO or VCO.

i btw. have them react the exact opposite way around... turning the pot left, makes the slope faster... but, it's simply a matter of getting used to it...

Have also a few other modules (2-3) where i have the pots reversed... sometimes i can force myself to correct this but i am also good at ignoring it...

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