Hi,
@albgg:
You are correct, but not in general, but as a special case.
With special cases you can explain almost anything.
*****
Imagine a black box. It is an amplifier.
* One input is the (varying) signal "S"
* One input is the somehow fixed gain "G" (volume)
It has one output "O"
Then the amplifier (or multiplier) has the mathematical formula: O = S x G
Example: let's say the input "S" changes: -2 / -1 / 0 / 1 / 2 (maybe volts)
Lets say gain is 4.25. (it has no unit)
The output is: -9.5 / -4.25 / 0 / 4.25 / 9.5 (volts)
If gain is set to 1.5:
The output is: -3 / -1.5 / 0 / 1.5 / 3 (volts)
With a multiplier (or amplifier) if one input is zero, then the output is zero, too.
If signal input of an amplifier is zero, then the output is zero.
If the gain if an amplifier is zero, then the output is zero, too
*****
Now a adder. The mathematical function is: out = A + B
One input of an amplifier is surely the signal input,
The output is surely the signal output..
But your solution has a couple of adders: let's say gain = 3 and signal = 5.
The you have two adders: 5 + 5 + 5...
Hiw many adders do you have with a gain of 4.25?
****
An example for an adder is when you make a mono signal from two stereo signals.
M = R + L. Two inputs, one output.
All have the same unit (volts)
If R = 0, then the output is just L...
Klaus