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

[Tom Wiltshire]

That's a better way to do a single HP pole. The 1-pole SVF method I posted uses an extra op-amp to achieve the same effect, so Olivier's way is much better.

T.

On 11 Mar 2014, at 14:34, Olivier Gillet <ol.gillet at gmail.com> wrote:

> 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
>> 
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy