[sdiy] Yusynth Transistor filter

[Oakley Sound]

> In both cases the resistance in the middle setting should be considerably lower than half the maximum resistance.

I don't think this is the case. For a 50K log pot the mid point would
give approximately 45K when used as a variable resistor with a
decreasing resistance in a clockwise rotation - ie. approx 90% of the
track resistance is left to go as you turn it towards minimum resistance.

For a 50K rev-log pot it should be around 5K thus giving us the required
sensitivity at high resonances in the Moog ladder.

Using a 500K linear pot with a 50K resistor in parallel with its
connected terminals will give 45.5K at minimum rotation when wired to
reduce its resistance when turned clockwise. At mid point it would be
41.7K, approximately 10% less than full resistance. This is more like
log behaviour.

At this point my head is about to explode...

But the other thing to remember for the Moog ladder is that the pot is
acting in conjunction with the low value base resistor of the left hand
transistor of the lower NPN pair. The two together effectively acts as a
linear attenuator... replace that variable resistor with a low impedance
linear volume control and it'll sound the same.

Tony