Question about PT2399 chorus pedal LFO settings

[diablochris6]

I was looking at a few of the PT2399-based chorus pedals floating around the web and noticed that the voltage ranges of the LFOs varied quite a bit, according to the simulations I ran. The EQD Sea Machine (schematic on Madbean's site as the Gravity Wave) has an LFO that goes from 0-9V but is attenuated down to ~850mV. The Jenny Greenteeth has a LFO that swings about 1V, but the bottom of the waveform sits around 4V and swings up to 5V. I forgot the what the Little Angel's range was, but I recall that the swing was almost 1V. The Little Angel also has the LFO signal run into pin 2 of the PT2399 as opposed to pin 6 like the other circuits, so I don't know if it can be lumped in the same group as the other two.

I guess my question is, does the range of the LFO matter as long as it doesn't surpass the voltage limits of the PT2399? Is the swing (~1V) the more important value to look at here?

[anotherjim]

I guess it depends on how the pin6 modulation is done. Delay time is set by the current going down to 0v from pin6, this will not directly correspond to the LFO amplitude. You may see the LFO wave on pin6, but that's being imposed, the chip internals want to keep pin6 at a nominal 2.5v with any supported delay setting.

You're correct that modulation of pin2 is a different thing - not how the chip design intended and therefore undocumented.
In every case, the chip supply volts should be exceeded on any pin.

[duck_arse]

......  .......

[anotherjim]

Nah mate, I'm in the mood to let it stay.

[ElectricDruid]

I guess my question is, does the range of the LFO matter as long as it doesn't surpass the voltage limits of the PT2399? Is the swing (~1V) the more important value to look at here?

I think the range of the LFO definitely matters. As you've pointed out, whether you're feeding pin 2 or pin 6 (and in that case, how) makes a difference. In the Pin 2 case, you're shifting the bias point of the delay, so you're reducing headroom either top or bottom, depending which way you go.
For Pin 6, if the LFO is just fed in via a resistor, you're controlling the current that flows out of Pin 6 by changing the voltage across the resistor that hangs off it. Usually that would be down to ground, and as we know Pin 6 is supposed to be at 2.5V, so if the bottom end of the resistor is suddenly at 1V not 0V, then the voltage across the resistor is less and the current drops.
There are other ways, like using a BJT or a vactrol to control the current. Those will also have their own sweet spots in terms of LFO range and depth. But in all cases it makes a difference, as far as I know.

HTH,
Tom

[diablochris6]

After looking at the rest of the circuitry leading to pin 6, this makes sense. Thanks for the answer, gents!