correction & question, Re: [sdiy] SSM2044 Filter schematic??

[john mahoney]

----- Original Message ----- 

I had written:
> Here are the differences between the SSM and Barry Klein circuits:
>
> (3) Between pins 1 and 15, there is a pair of 200 Ohm res on each circuit,
> but BK has 3300 pF caps in parallel with each of them (the SSM circuit has
> no caps there)

When I wrote that, I was overlooking a Ground connection that was lightly
hand-drawn on the Klein schemo (as a correction to it, heh...).

Pins 1 and 15 of the SSM2044 are the Signal Inputs; yes, there are 2 inputs.
Each input is padded by a fixed resistor. (68K on pin 1, 100K on pin 15.
There is a reason for the imbalance but it's irrelevant here.)

Correction: Between each pad resistor and each input pin is a 200 Ohm
resistor to *Ground*. (The pins are not really connected to each other, as I
had suggested).

Klein adds a 3300pF cap to Ground in parallel with each 200 Ohm resistor.

Question: Are these caps to eliminate DC offset?

I wonder why SSM didn't specify those caps. Probably just an oversimplified
design on the datasheet? Maybe it was like a Jedi mind trick: "These aren't
the signals you are looking for. There are no stray DC voltages in an
SSM-based synthesizer. These signals can pass through..."
--
john