• 10-11-2005, 01:26 AM
    Kaboom
    Some clarification needed concerning volume controls...
    Mkay, this has been lurking in the back of my mind for a while, and unable to solve it myself, i have decided to ask ye, oh knowledgeable AR member, for help.
    Volume controls are nothing but pots right? So they can ONLY attenuate the signal, right?
    therefore, is the volume control in a preamp set before or after the amplification stage? If its set before, then as you turn the voltage up and down you are effectively varying the input impedance of the preamp stage aren't you?
    if its after the amplification, then wouldnt you be varying the output impedance of the amp?
    Also, I am guessing a resistor is a resistor is a resistor, therefore no matter how lousy the quality of the resistor is, it cannot in any way affect the signal quality right? Therefore I assume that the point of using expensive resistors is because the resistance measurements in them are more precise, therefore making it easier to closely match the values of resistors in both channels. Is this assumption correct?
    please help, this is almost keeping me from sleep at night!
    cheers!
  • 10-12-2005, 07:29 AM
    JoeE SP9
    Quote:

    Originally Posted by Kaboom
    Mkay, this has been lurking in the back of my mind for a while, and unable to solve it myself, i have decided to ask ye, oh knowledgeable AR member, for help.
    Volume controls are nothing but pots right? So they can ONLY attenuate the signal, right?
    therefore, is the volume control in a preamp set before or after the amplification stage? If its set before, then as you turn the voltage up and down you are effectively varying the input impedance of the preamp stage aren't you?
    if its after the amplification, then wouldnt you be varying the output impedance of the amp?
    Also, I am guessing a resistor is a resistor is a resistor, therefore no matter how lousy the quality of the resistor is, it cannot in any way affect the signal quality right? Therefore I assume that the point of using expensive resistors is because the resistance measurements in them are more precise, therefore making it easier to closely match the values of resistors in both channels. Is this assumption correct?
    please help, this is almost keeping me from sleep at night!
    cheers!

    The volume control is after amplification. Your other assumptions are essentially correct especially about channel balance and matching.. The only way to have a constant output impedence in a "pot" is to use a ladder attenuator. They have a constant impedence characteristic but are not inexpensive.http://forums.audioreview.com/images/icons/icon6.gif