How does Veils 2020's offset feature work?

Eurorack
#1

I recently switched up to a Veils 2020 from the old Veils and I’m a little confused but some of the behavior I’m seeing.

I’m trying to attenuate and offset an LFO from Stages. The response curve is set full CW to linear. When I have the slider all the way up and monitor the signal on the scope, I’d expect to see the LFO go from 0 to 8v, but it actually goes above the limit on my O’Tool Plus (12v). Judging by the timing, I’d guess it’s going up to 16v (double the original signal). Shouldn’t the slider all the way up be unity gain?

Ok anyway, my goal is to get the range of the LFO around 2v to 3v, so I attenuate the signal down so that it goes from 0v to 1v and now I’ll use the offset trimmer to bump it up 2 volts so I’ll be in the range I want.

However, when I turn the offset trimmer, it appears to scale the voltage up, not offset it. If I turn the offset to roughly 12 o’clock, I can observe that the LFO is now swinging from 0v to about 7.5v. The offset seems to be applying gain???

So I’m not sure what’s going on here, but it really doesn’t seem right. Hopefully I’m overlooking something really obvious?

Veils 2020
#2

Veils can amplify a signal.

From memory, on the linear response setting it is x2 gain. ie: 2 x 8V = 16

Again from memory, I think the amplification of the extreme exponential is x20. At some point amplification will cause the circuit to overload and it will clip.

Therefore you could use your scope (or ear) to determine where unity is (depending on the response curve) and then attenuate and offset from there.

#3

I’d be really surprised if the linear response was supposed to be something other than unity gain. Anecdotally, every VCA I’ve ever used has been unity gain (except when there is an additional control for the curve or explicitly gain).

from the manual (emphasis mine):

C. Gain CV amount. Amount of gain (amplitude) modulation from the CV input 24), or direct gain control when no cable is patched in the CV input. When set to the maximum, a CV of +5V yields a gain of 1 (0dB), and a CV above +5V might cause distortion.

While it doesn’t explicity say slider at max and no CV input patched is unity gain, it seems strongly implied to me.

Even if it were meant to be 2x gain, the offset is definitely not behaving like an offset.

@pichenettes can you offer any insight?

#4

I might have missed something in your comments, but the CV input is normally to 8v when nothing is plugged in.

So with the slider at full, and nothing plugged into the CV input, it would be amplifying the signal above unity gain. For unity gain I think you’d want the slider a bit over half way, so the 8v normalled to the CV input would effectively be being attenuated down to 5v by the slider.

#5

Thanks. I can confirm that this is consistent with the behavior of my module. When I patch a static 5v into the CV input, it does indeed output at unity gain with the slider all the way up. So I guess that resolves that part.

But the offset is still not working as an offset so that case remains open!

#6

Your module behaves normally, and consistently with what is described in the manual.

You cannot do that with Veils - or at least the way you are using the module.

The offset control on Veils offsets the CV, not the output or input signal. You can offset the modulation of the main signal.

In other words, the output is (CV x cv_amount + offset) x input_signal.

The slider to the maximum means that the CV will not be attenuated.

The CV input is normalized to a constant 8V, and unity gain is achieved with a CV of 5V.

Thus, with nothing patched in the CV input, and the slider to the maximum, a gain of 1.6x will be achieved.

Because it is an offset on the CV. So you are indeed adding more to the +8V normalized to the CV input.

There is one way of patching the module to achieve your goal, though… Patch a constant +5V signal in the signal input of Veils, and patch your LFO in the CV input.

3 Likes
#7

Thank you for taking the time to give such a thorough explanation! I totally misunderstood the use of the offset. It all makes sense to me now :slight_smile:

#8

How Veils behaves with the LFO into the signal input, and nothing in the CV input:

Try changing offset and slider. Observe how the response only gives a larger or smaller range of gain. You’ll notice that the CV is held at +8V (what the module receives internally when nothing is patched in the CV input).

How Veils behaves with your LFO patched into the CV input, and a constant +5V in the signal input:

Observe that you can use the response knob to waveshape your LFO and make it more peaky, and that the offset knob correctly behaves as an offset.

3 Likes
#9

Desmos is unreasonably fun.