Tau Systems 1010 Filter

[Jim Patchell]

    Well, I hope to be able to answer some of these questions soon, but, I am in
the middle of several things right now, including moving and caring for a sick
kitty.  Puts a strain on both time and pocket book.  I am as curious as you and
others probably are.  I will keep you all posted once I get it hooked up.
Unfortunately, I have nothing to compare it to, sonically speaking. (I have no
other Ladder filters).

    -Jim

WeAreAs1 at aol.com wrote:

> Hello Jim and DIY folk,
>
> <snip>
> Jim, I can see why you think the mystery part at the output is an OTA and an
> opamp.  It would appear that the signals from the FET's enter the differential
> inputs of an OTA (probably a 3080), with the OTA control current connecting at
> Pin X (strapped "on" by the 39K resistor to ground).  The signal then goes on
> to an opamp, but is it entering the opamp through its inverting or non-
> inverting input?  It's likely R29 and R30 are the feedback loop of the opamp,
> controlling its gain, connecting to pin S at the opamp's inverting input.
> It's also possible that pin R (the Highpass input) connects to its non-
> inverting input.  Maybe I'm dense, but I get lost trying to figure out signal
> phase going through all those transistors...  There may be some internal
> resistors that we can't see, between the OTA and the opamp.  I'm assuming also
> that there are some power connections on the part that you didn't include on
> your drawing, right?
>
> Does this filter really get Highpass response simply by inputting audio at the
> Highpass input, or must some signal also be input at one of the other inputs?
> (at the inverting Lowpass input?)  One would think that Bandpass response
> might also be available by putting equal amplitude signals into both the
> Highpass and Lowpass inputs.  Does this make sense?
>
> <snip>
> Michael Bacich