[sdiy] Steiner filter mods

[HOSHUYAMA]

Hi Fabio,

Important thing is just to keep the current of the differential
pair.  Any type of current source should be OK.  Of course, you
have to adjust V/Oct scale.

Actually, R13 is not needed.  I used it just because the PCB
from Motohiko has the holes and I thought it will save the
circuit in case of accident.

If you used an JFET with large Idss for Q2, maybe you should
connect the gate of Q2 to -15v directly to get appropriate
current.

Sam HOSHUYAMA

fmg wrote:
> HOSHUYAMA wrote:
> 
>>Hello List,
>>
>>I also built a Steiner-style filter with simple modifications.
>>
>>Schematic:
>>
>>  http://houshu.at.webry.info/200511/img_1.gif
>>
>>Constant current source Q2 reduces common-mode gain of the
>>differential amplifier to almost zero, resulting in far less
>>CV feedthrough.
>>
>>Another modification is the output point to the buffer U1.
>>Response of the resonance pot is more like Korg MS20.
>>
>>I also used a diode limiter as Yves Usson.
>>
>>Sam HOSHUYAMA
>>Saitama, JAPAN
> 
> 
> Sam,
> 
> Shouldn't gate of Q2 be directly to -15V?
> I don't understand how Q2 keeps current constant as is. Was a
> drawing mistake? I'm confused.
> 
> Fabio
> {I want an anatomical zoom
> /Soda Stereo}
> .
> 
>