Feeding a linear VCA with an envelope generator

What’s the way to do this as you would do it on the analog domain ? Triggering the VCA level with an envelope ?

Super easy:

Add the VCA

Select it, the smaller screen will allow you to enter the subchain, set an input source for the gate trigger and then add an ADSR unit. Exit that, Set the vca gain and bias to taste.

If you take a look in the getting started videos, there’s a video near the top on making a synth voice that goes through it:)

Thanks Neil !

Newbie here. Apologies, if the following should be in a new thread. I’m afraid I’m still confused by the control signal flow on the 301. Why add the trigger to the VCA and not the ADSR (as I would do in the analog domain)?

  • Scott

Welcome @scott.lepore

That’s not what’s being suggested.

The ADSR does go in-between the trigger and the VCA; so you have a VCA, underneath that you have a separate chain with it’s own input, after that input, still in the VCA input chain, you add the ADSR.

Does that help?

Thanks for getting back to me, kel. Perhaps I’m confused by the object model. Are you saying that by adding the ADSR into the VCA, I’m putting it before the VCA? Seems like I’m putting it inside the VCA object.

Perhaps I add the trigger to the VCA object to allow it to be accessed by any sub-module?

No worries, we will get there :slight_smile:

In a sense yes you could describe it that way, you are putting the trigger inside the VCA object - the ‘inside’ is just its input - that’s all!

This is analogous with patching a trigger to a VCA - the VCA would jump suddenly up and down.

But a better way to describe it is that you have your top level Audio Chain, in which there is a VCA, and then you have a whole new chain inside the VCA that has it’s own input which can be anything.

So, by assigning your trigger to the VCA Chain and placing an ADSR in there you change that trigger into an envelope.

Are we there?

Thanks for confirming. So this signal chain does not work the same way that an conventional VCA and ADSR would.

Can the trigger, assigned to the VCA, be used by any object inside it?

It’s not the VCA’s input, instead the VCA’s internal chain is related to the level control parameter of the VCA… which happens to be the only parameter you can externally control in this specific unit.

So, like a real VCA, you have your ADSR wired to the VCA’s CV in. In ER-301 world, the VCA level parameter has a sub-chain, and this in essence is the VCA’s CV control. Here you can assign an external CV signal, an ADSR unit, or whatever you’d like control the VCA level parameter).

When it opens, anything to left of the VCA unit is treated as signal input. It could be used for Audio or CV… your option.

If you assigned a trigger directly to the VCA level control, you’d only here the VCA open for the length of the trigger.

If you insert the trigger in the signal input of the VCA, you’d most likely hear that blip if the VCA is routed to an audio output.

So, you’d want to assign the VCA level control to i.e.: an external trigger source, add an ADSR unit following and then you’ll have a traditional ADSR / VCA combination.

Here’s a visual:

1 Like

Hehe, penny just dropped on what the misunderstanding was :smiley:

Thanks Neil and Brian for chiming in. (Seriously impressed with everyone’s engagement level - fantastic response time!)

Neil, I believe I follow your block diagram. It is how I imagine the signal path to our hypothetical VCA unit would work. The part that still is confusing me is why the gate isn’t directly assigned to the child ADSR, rather than the parent VCA.

Brian, I follow your block diag. Does running the gate into the parent VCA (as opposed to the embedded ADSR) make it available to all units inside the VCA? (a kind of inheritance?)

1 Like

because the ADSR’s trigger input is to the left of the unit (it’s listening for a gate). The only subchain controls for the ADSR are each of the A/D/S/R stages of the envelope.

Sorry. Should have said that I follow what you’re saying here. It’s just that I’m used to gating ADSR’s not VCA’s. That’s what’s confusing me.

Let’s change tactics :smile_cat:

What is making you think a gate is being assigned to the VCA?

You still are. The gate should be triggering the ADSR, that’s within the VCA’s level control subchain.

If you assign the gate directly to the left of a VCA, it’s essentially like wiring a CV control into the VCA input… which is what you don’t want.

does this help?


Good idea, Brian. Perhaps the confusion is terminology, or UX related.

I’ll create hypothetical chain to clarify.

  1. I insert a Sine Osc (and assign a V/oct external source (A1) to control the V/oct). Level is set 1. I hear a varying pitch sine.
  2. I “up” to the top of my chain, scroll right and insert a Linear VCA (to modulate the output level of the Sine Osc)
  3. I select the level parameter of the VCA and in the sub-chain window (sorry, if that’s not what is it called) select an external gate in (let’s say from A3) (this is why I think I’m assigning a gate to the VCA)
  4. Still inside the VCA sub-chain window I insert an ADSR unit and alter the params to create a brief envelope
  5. I “up” to to top level again, select the level of the Linear VCA and set its gain to 1 in the sub-chain window

This works great. I’m hearing what I expect. It just seems I’m assigning a gate to the VCA rather than the ADSR.

My apologies if I’m being dense. (Wouldn’t be the first time.)