[sdiy] Yet more questions: best VC drive approach

Jacob Watters jacobwatters at gmail.com
Fri Nov 9 13:15:19 CET 2018

Yes in the VCA and not the integrator. I find that OTA's don't sound nice
when overdriven. They have a crackly, noisey sound. I prefer to do my
overdriving in a 4069, like the wasp filter.

On Fri, Nov 9, 2018, 3:48 AM Rutger Vlek, <rutgervlek at gmail.com> wrote:

> Hi Jacob,
> This also ensures that the clipping happens in the chip used for the
> integrators, and not in the OTA's, which sound bad when overdriven.
> I presume you refer to the OTA in the VCA that controls the drive level?
> Or do you mean OTAs inside your integrators? In the latter case I don't
> understand what you're saying (sorry)...
> Rutger
> *Jacob Watters*
> Web & Multimedia Specialist
> JacobWatters.com <http://jacobwatters.com/>
> Tel: 226-886-3526
> On Thu, Nov 8, 2018 at 3:32 PM Rutger Vlek <rutgervlek at gmail.com> wrote:
>> Hi guys,
>> I've been wondering about many things lately, hence the flood of emails
>> to the list :). I also have to admit feeling a bit stupid about having to
>> ask this.. but here goes:
>> What's the best approach to designing a voltage controlled overdrive? The
>> obvious solution I can think of is having a saturation element preceded by
>> a VCA. While I haven't fully done my homework on it yet, my guts tell me
>> that this isn't the best circuit in terms of noise behaviour, as it would
>> require the saturation element to be at high gain constantly while the VCA
>> various input level. Meaning that any VCA noise would be amplified by the
>> full gain of the saturation element. In guitar stomp boxes, some design
>> place a pot in the feedback loop of an opamp to change gain. Could a
>> similar approach work well for a VC-drive unit and would it perform
>> better/worse than the first solution I proposed?
>> Finally, I've been thinking about making drive level voltage controlled
>> via power supply to the saturation element (transistor in this case).
>> Feeding the control voltage into a buffer that puts out the supply to a
>> transistor would also allow to change drive level.
>> What do you think? How it this typically done? I just bought a Novation
>> Peak, and am impressed with it's three stages of overdrive although it
>> suffers from noise issues due to the amounts of again at hand. It makes me
>> wonder how I would design such a stage myself.
>> Rutger
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