April 4th, 2021, 3:50 pm
FerdinandII wrote:I was just trying to disabuse the OP of the following statement he made:
"...gain Controls reduce the voltage by impedance matching..."
In order to dispute this false concept, I chose to go back the the basics, ala Thévenin.
This concept kept creeping back into the discussion above and it needs to GO and never come back.tomp wrote:FerdinandII wrote:You need to just forget the concept of impedance when looking at this issue. It is irrelevant.
V=IR
The line level output is (generally) a voltage source.
April 4th, 2021, 3:56 pm
Cogito wrote:[As Roscoe and others suggested, gain controls are potentiometers. Pots control the volume by manipulating the preamps input impedance.
April 4th, 2021, 3:58 pm
Cogito wrote:Amp’s’ gain factor being constant, lowering the voltage seen by its gain stage reduces its output voltage. As Roscoe and others suggested, gain controls are potentiometers. Pots control the volume by manipulating the preamps input impedance.
April 4th, 2021, 4:01 pm
DaveR wrote:Cogito wrote:
There are different ways to implement a circuit that controls gain. A passive circuit can only reduce amplitude.
April 4th, 2021, 4:14 pm
Roscoe Primrose wrote:DaveR wrote:Cogito wrote:
There are different ways to implement a circuit that controls gain. A passive circuit can only reduce amplitude.
Actually, a passive circuit can only reduce power. It can increase voltage at the expense of an increase in output impedance.
Roscoe
April 4th, 2021, 4:23 pm
April 4th, 2021, 4:27 pm
Roscoe Primrose wrote:Cogito wrote:[As Roscoe and others suggested, gain controls are potentiometers. Pots control the volume by manipulating the preamps input impedance.
For the last damn time, no, they do not. If you need further clarification, see my signature line.
The variable resistor (aka potentiometer) changes the source impedance seen by the following stage, but not the input impedance. The "gain" control on just about every amp that has one is a no different than the "volume" control on just about every amp that has one.
April 4th, 2021, 5:27 pm
Cogito wrote:...I was planning to use a an existing preamp between plllxo and the subs for level matching.. My goal is to avoid pots in the system. ...
FerdinandII wrote:I'm out. I should have listened to Walt.
All these people trying to explain the Theory of Relativity because the wrong amp in their system has the highest gain......
April 4th, 2021, 5:38 pm
Roscoe Primrose wrote:Cogito wrote:[As Roscoe and others suggested, gain controls are potentiometers. Pots control the volume by manipulating the preamps input impedance.
For the last damn time, no, they do not. If you need further clarification, see my signature line.
April 4th, 2021, 5:51 pm
Jim G wrote:...I'm out of my league with the theory being discussed, but wouldn't one use an amplifier with a gain control to reduce the overall gain of the 4 way passive system to match the subs? This will reduce overall system noise as well. I can only imagine this system will be quite noisy?