Quadrax CV control of rise/fall times

I am a little confused about how the cv inputs are effecting the rise and fall times for the quadrax.

On my other envelopes (for example the falistri) the cv just adds or subtracts from the position of the rise or fall knob. On the quadrax I feel like it is doing something else…

For example if I am doing a krell patch and I have another envelope going into one of the cv inputs to control rise time, then if that cv input decreases suddenly (for example a quick decay on the envelope that is going into the cv input) the quadrax seems to just snap to EOR. If the quadrax envelope is controlling a VCA the volume of the oscillator can go from very low to maximum instantaneously, it is very jarring.

I can even put in just a +5v offset into the cv and as I manually start turning it down the same thing happens and the quadrax just seems to jump to EOR all of a sudden.

None of my other envelopes do this.

Are you able to get some scope shots of the behaviour? Maybe you are just turning down the rise too much so it’s basically instantaneous? Have you tried other levels of attenuation.

I just tested this out on a Quadrax here, using Planar to control the rise time of the envelope and it works exactly as expected. As more positive CV is applied the rise time gets long (very long at +5 since the inputs track 1v / octave) or short (very short at -5 for the same reason).

I don’t have a scope unfortunately. But for example try setting the dials for rise and fall at 12 o’clock and putting in a cv controlling rise time. I can put in a positive offset of 5 volts for a very long rise time. If however I put in the positive +5v offset and then decrease it quickly to say +2-3v then it instantly goes to EOR (I can hear it happening and the EOR led goes on on the QX expander).

It’s not really something that’s possible to have variation from unit to unit, they are all running the same firmware and the envelope times are controlled entirely by firmware.

The behaviour you describe is normal, because the way the time settings work is the envelope will try to conform to the newly given stage time. An example: if your initial attack time is 0.5 seconds but you use 1V of modulation to step it up to 1 second, and then at 0.4 seconds you set the modulation back to 0V, the envelope will change shape so that it finishes 0.1 seconds later. If you were at 0.6 seconds and set the modulation back to 0V then there would be a sharp rise, because the 0.6 seconds exceeds the 0.5 second time, and it would immediately hit the end level for the stage and move to the next.

Ah ha, thanks for the reply, this is exactly what I started thinking was happening but couldn’t quite put words to it. I am used to analog EGs that don’t have a ‘memory’ of how long the attack was initially set for.

I imagine there must be some reason for doing it this way instead of just changing the slope of the attack based on the cv input? For example, if I was at 0.6 seconds and then set the modulation back to 0v it wouldn’t jump to EOR but the position would stay where it was at at 0.6 seconds and the slope would just change back to being the original steeper curve of the initial attack time. The current behavior makes some things difficult to do (like a krell patch because of all the instantaneous jumping up and down), but if there are benefits to it I would love to know those too :-).

Thanks again!

It is beneficial for rhythmic applications because you can easily return the original programmed duration of the envelope even with some intermediate modulation. I can definitely see the usefulness of the more “analog” mode though, maybe I will add that as an option in a future firmware.

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That would be great! There are no EGs I really love, and quadrax is the closest, it is just little things like this holding me back :wink: