In Lancaster's "Filter Cookbook"--- I think "k" was loop gain in a filter.
There is "Gain/Bandwidth Product" to consider, in a bandpass filter, the 
higher the gain, the more the bandwidth is contracted. 

"Q" too high and the filter becomes an oscillator. Had that happen once on
on multi-order state-variable filter I built. I cut the band limiting part
of the filter too close, creating an edge condition. It teattered on the
edge and didn't take much to push it into oscillation.

Keep it within the "Barkhausen Criteria" range, keep "K" and "Q" within 
controllable limits. High-Q filters are fun, but they can easily go wild on
you. Hardware analog versions can be tamed, digital version should be easier.


Enjoy, cheers,
-Partev


==============================================================================


--- rorywalsh@ear.ie wrote:

From: Rory Walsh 
To: csound@lists.bath.ac.uk
Subject: Re: [Csnd] mode opcode and kQ
Date: Thu, 17 Mar 2011 22:06:55 +0000

1.5 represents a ratio of 2:1 which is an octave.

On 17 March 2011 19:15, Stefan Thomas  wrote:
> Dear Rory,
> thanks for Your explaniations.
> What I don't understand till now is:
> why is 1.5 an octave? Shouldn't it be 2?
>
> 2011/3/17 Rory Walsh 
>>
>> Q is centre frequency over bandwidth. Higher vales for q will make the
>> filter more selective. It can also be used to filter particular
>> musical intervals. A Q value of 1.5 will filter one octave. A perfect
>> fifth is 2.5. Some filters let you set the bandwidth, others let you
>> set the quality factor. It depends on the particular filter opcode you
>> use.
>>
>>
>>
>> On 17 March 2011 08:50, Stefan Thomas 
>> wrote:
>> > Dear community,
>> > I have a question about the mode opcode.
>> > I don't understand exactly what the kQ parameter does.
>> > Could be someone so kind to explain it to me?
>> > Thanks,
>> > Stefan
>> >
>>
>>
>> Send bugs reports to the Sourceforge bug tracker
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>> csound"
>>
>
>


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