'Comparator' is the actor you want. However, I suggest triggering not when a value == a specific value but rather when is greater than or less than.
This will help ensure a trigger is sent. When comparing Decimal numbers it is possible the value jumps past without ever being tested at a time when it equals the value you are looking for.
For example, the value from the envelope generator may be ramping up, and you want to send a trigger when the value is equal to 75.
The values is getting close, its 74.85.... now on the next Isadora cycle the value is 75.1... Your test fails because the value never equals 75.
So testing if the value is greater than 75 will ensure that it triggers.
Another option, I sometimes use is to 'round' the incoming float to an Integer. You can be rather sure the Integer will occur during a cycle (although still a risk if its a very quickly changing value).
Use 'Float to Integer' actor to convert a float to an integer (a number of conversion options are given, including Round)