Analogy of the Electron and Air Resistor

[Phend]

Imagine a pneumatic circuit using a tube with, for comparison, 1 ohm of resistance.
Now add an extremely small tube coming off of it with a resistance of 1M ohm.
Assume the 1R tube is 1 inch in diameter, so the 1M ohm tube is 1 million times smaller.
So I think.
Very small.
I see an effect circuit that has a 1M resistor from a PNP collector to 9v And pin one of a LM13700.
From the pneumatic sense, sounds like a plug?
Question / Discussion:
Hum, why it is the 1M resistor there at all?
Re,Musitronics Micro V Envelope Filter R16

[Rob Strand]

see an effect circuit that has a 1M resistor from a PNP collector to 9v And pin one of a LM13700.
From the pneumatic sense, sounds like a plug?
Question / Discussion:
Hum, why it is the 1M resistor there at all?
Re,Musitronics Micro V Envelope Filter R16

It sets a minimum current through the OTA, and that sets the lowest frequency of the filter ie. the point where the sweep starts.

In theory that small current could come via the transistor by adding some DC bias.   For some circuits that works and is done but for others a fix resistor is a better design choice because the small current from the transistor might not be well defined or stable as a simple resistor.

The added resistor also helps define a threshold point for the detector.  For the circuit to sweep the transistor current needs to approach the current from the 1M resistor before the sweep will give the appearance of starting.