[sdiy] Deciphering Roland 100 filter schematic

[Samppa Tolvanen]

Hey, this ain't that bad? ;)

On 4/21/08, Aaron Lanterman <lanterma at ece.gatech.edu> wrote:

>
>  1) There's a row of pots at the top of the filter (on the schematic), that
> is that have notations like "100kA" and "100kB". VR305 is like that too,
> it's marked "100 kB". Any ideas of what the A and B notations mean?
>

Wouldn't we this time be pretty sure "B" stands for Linear and A for
"Log". standards standards...

>  2) Several of the caps, such as C321, C322, C323 have notations on them
> like "10/16 N.p" and "100/16." I'm guessing N.p means "not polarized," but
> I'm not sure about the slash notation. What do those notations mean? They
> look like something from the mad hatter in Alice in wonderland. (Most of the
> other caps have microfarad markings.)
>
I'd go for 10uF/16V ect.

>  We're also trying to decipher the resonance pot. There's two variable
> resistors ganged together.
>
>  3) What do the circles that are tied to ground just below the variable
> resistors indicate?
>

Connection is run thru shielded cable.

>  4) Related to 3 - should we interpret the variable resistors as one end
> tied to a pot, another end tied to the wiper, and the other end left
> floating? Or is that ground marking somehow important?
>

Yes. (see H.P.F.)

>  5) I see what the "right" resonance pot is doing - it looks like it
> controls the amount of feedback to the negative part of the diff pair at the
> bottom of the diode ladder. But what is the other pot, the one that connects
> "A" and "B" (just to the upper right of FET Q314, which looks to be a
> buffer) doing?
>

Wouldn't that be sort of "gain correction" for the high Q-settings,
R351 paralled with R352 and resonance pot combination?

...Samppa