How to passively shift logic levels to drive LEDs
Zener diodes do not conduct in the reverse direction until their breakdown voltage is exceeded.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A simple solution.

How it works:


A 3.3 V Zener requires a voltage > 3.3 V before it will experience reverse breakdown. At 2.7 V input the Zener will not conduct and D2 will be off.
At 9 V the Zener will breakdown and 3.3 V will be dropped across it. You didn't specify the LED colour so we'll assume 2.2 V is dropped across it which leaves 9 - 3.3 - 2.2 = 3.5 V to be dropped across R1.
Setting R1 to 470 &Omega; will give a current of \$ \frac {V}{R} = \frac {3.5}{470} = 7.5 \ \text {mA} \$.


Your input signal needs to be able to source that much current or else you can't do this passively.