[sdiy] Aries modular schematics detail

[harry]

The Aries State Variable Filter has a tempco... if you trace the layout you will
see the  pads where the tempco connects.  The giveaway is the spacing... much
too long for a standard resistor... its got to be a Q-81.

I will not entertain requests to crack open the block to make sure  ;^)

H^) harry

Grant Richter wrote:

> Here are some educated guesses. Since the replacement circuits work like the
> originals they are probably not too far off in design.
>
> > "a series of carefully selected and temperature compensated
> > components which have been potted together as part of the printed
> > circuit board.   The effect of this potted block is to create
> > exponential currents in R13 and R31 as a function of the voltage at
> > the junction of R8, R10 and R11."
>
> This is just Terry Michaels NPN-PNP exponential converter. That is to say, I
> replaced a broken block in an Aries state variable filter with Terrys
> circuit and it worked fine. If you look at it carefully you can see the
> emitter resistor for the NPN follower and the current limiting resistors for
> the collectors of the two PNPs. As far as I know the blocks just contained
> matched transistors, but there may also be a tempco in there for the VCO
> block.
>
> >
> >> Also, the module 329 Flanger has a part called PD10 with no other marking.
> >
>
> Think of a dual string of diodes (or diode connected transistors) with
> capacitors in parallel with the diodes. The AC impedance of the diodes is
> varied with a control current and forms an allpass network in parallel with
> the capacitor. The circuit is nearly identical to the Tau Systems phaser. It
> is very similar to the Moog transistor ladder filter in the way the signals
> are input and output from the ladder element. But the change in capacitor
> position makes it an allpass instead of a lowpass. The literature says it
> produces 5 notches, which would correspond to 10 stages.