@Your Uncle Bob's comments on the OP:
The Lamp reads a Monophonic audio signal in Hertz and updates it's LED-style display accordingly.
A Reaktor Instrument can be either Monophonic or Polyphonic:
And many of the modules also can be set to Mono (or not):
As indicated in bottom right of the module:
(Notice the RED Xs when a Poly signal is sent to a Mono input.)
When an Instrument is running in Polyphonic mode, each of the modules, instruments, etc, is actually a template that is duplicated for each of the polyphonic voices.
The Lamp is a mono-only module, so it will not accept polyphonic input. One option is to use a Voice Combiner module between the Poly module and the lamp:
Another option is to use a From Voice module, specifying which voice to send to the Lamp. In the following case, we use the lamp to display the frequency of an Oscillator being used as an LFO:
This set-up doesn't work terribly well because the
Amplitude knob on the LFO, if turned all the way down, removes ALL amplitude from the Volume Envelope.
Another module to be aware of is the Event Smoother:
This will change the effect of the Square LFO above from sounding like Deep Deep Deep, with hard edges (and some clicking), to Weep Weep Weep, with soft edges.
I'm still pretty green as is obvious, but there's the basics for anyone else who's troubled with the Lamp.