[sdiy] 'Reverse' connected 2164 approach for HP filter stage purpose..

[Olivier Gillet]

Hi Jean-Pierre,

As far as I know, you want low-pass and high-pass filters (1 / (1+s)
and s/(1+s)), not integrators and differentiators (1/s and s). This is
a hint that you'll need one more resistor in the LP and one more
capacitor in the HP...

In the LP nodes, you'll need a resistor from the integrator output
back to the 2164 input.

In the HP nodes, you'll need a cap from the op-amp output back to its input.

http://i.imgur.com/hkMeQYQ.png

Best,
Olivier

On Tue, Mar 11, 2014 at 2:54 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
>
> On 11 Mar 2014, at 13:26, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:
>>
>> BTW is there anybody who used the 'reverse' connected 2164 approach
>> for HP purpose like the first 2 stages hre ?
>>> http://www.arcenson.com/public/2164_BP_filter.JPG
>>
>> Didn't check it on breadboard so far...
>>
>> JP
>
>
> I haven't seen it before. The only VCA HP stage I know of is in one of the THAT VCA application notes, where they show a 1-pole SVF used as a HPF. Basically, a mixer followed by a VC-integrator, with the integrator output taken back to the mixer.
>
> I think I saw it first in one of the others, but it's also shown here:
>
> http://www.thatcorp.com/datashts/AES13-031_Digitally_Controllable_Audio_Filters.pdf
>
> Incidentally, there's a SVF in there with the 'phase lead' compensation components shown, and also an extremely "alternative" way of controlling the Q in an SVF by moving the CVs of the two integrators apart. Interesting stuff.
>
> HTH,
> Tom
>
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