[sdiy] Moog ladder filter with resonance compensation schematic

[Andrew Simper]

There are two places to compensate for the drop, either adding the
positive input signal to the negative feedback signal (output of the
filter) before resonance attenuation, or boosting the output signal
level by the resonance amount so out-gain = 1 + resonance-gain. The
latter will increase the level of self oscillation, the former will
not. For the output boost you would need a dual pot / dual VCAs, so
adding the input to the resonance path may be easier depending on how
the resonance path is done.

--Andy
cytomic - sound music software


On 25 February 2014 22:29, Michael Bachman <bachmanm50 at gmail.com> wrote:
> What I have seen is to mix a bit of the input, though a simple 1 pole
> HP filter into the resonance feedback.  I've done this on a 4 pole
> cascaded OTA design and it works pretty well.  It gave me back 3-4V of
> the output voltage drop that happens near full resonance.
>
> Here's my schematic.
> http://www.flickr.com/photos/96442572@N07/12771024023/
>
> On Tue, Feb 25, 2014 at 4:27 AM, Mattias Rickardsson <mr at analogue.org> wrote:
>> I guess the resonance feedback signal is mixed into the output,
>> raising it a bit as the resonance is raised?
>> I don't have the exact schematics though, sorry.
>>
>> /mr
>>
>>
>> On 24 February 2014 20:04, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:
>>> Hi list,
>>>
>>> I remember seeing a Moog ladder filter with resonance compensation
>>> schematic somewhere but can't remember where..
>>> You know the type of schematic with compensation
>>> to keep the signal from droping when lowpass resonance is crancked up..
>>>
>>> Many thanks.
>>> JP
>>>
>>>
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