I have a 2nd generation Veils module.
I really enjoy doing audio feedback with the module, by patching one channel’s output into another’s input and viceversa.
I’m wondering, though, whether I could damage the opamps, since the inputs are DC coupled, therefore feedback may end up generating an offset “cascade”, preventing which, IINM, is usually the reason why one would want AC coupled inputs.
I’m really happy, though, that Veils is NOT AC coupled, since I also use it a lot to process and mix control signals.
So, can anyone give me a bit of insight on whether I should be more cautious and give up the audio feedbacking games, or whether it’s all perfectly fine and I should just stop worrying ?
You should stop worrying, feedback will never grow under -12V or above +12V, which the circuit is designed to handle perfectly well
Mille mercis Emilie.
Suis rassuré, alors
So, am I right in assuming that the reason why inputs, in most “audio/final output” purposed VCAs, are AC coupled is :
- in order to avoid low frequency beats in the audio path,
but also and mostly :
- to save the components needed to keep the circuit from overloading
Or is there more to it ?
Endless thanks for your great work (et l’esprit qui allait avec😊).
You don’t need any component to prevent the circuit from “overloading” (whatever that means).
A VCA can be AC-coupled because if the input signal has a DC offset, then the control signal will bleed through and become audible: (signal + offset) x envelope = signal x envelope + offset x envelope – the second component being potentially unpleasant to hear if the envelope is fast enough to have frequencies in the audio range.
Thank you again for the thorough explanation.
That was pretty much what I was trying to assert in point #1 (“avoid low frequency beats in the audio path”), through my very limited vocabulary and knowledge of all things electronic.
My incorrect assumption for point #2, as well as for my general worrying at the source of this topic, came from reading (and most certainly misunderstanding) the sentence below by Ken Stone (Ken Stone's Modular Synthesizer) : “Feedback experiments require the use of AC coupled mixers such as these to prevent any op-amp offset cascading and driving the unit into distortion”
This can happen, but this is not something destructive or intrinsically bad. Just annoying as the output signal stays stuck at either +12V or -12V.