From: pallison49@gmail.com   
      
   Big Bad Bob wrote:   
      
   ==================   
   > Phil Allison wrote:   
   >   
   > >>> This might inject up to 1mV into pin 2 if the grid source impedance were   
   *10Mohms*. However, for a MM phono cartridge, the impedance is 1kohm at   
   50/60Hz and for a guitar PU about 10kokms.   
   > >>   
   > >> Actually it's more like 100k for a typical guitar amp pre-amp input,   
   > >>   
   > >   
   > > ** The source impedance is what matters, and is as I stated.   
   > >   
   > >  Guitar PUs and phono PUs are both low value resistors at 50/60 Hz.   
   >   
   > yeah, but a typical amplifier is going to have a 100k-220k in series   
   > with the preamp input for dual jacks.   
      
   ** 68k is most common value on guitar amps with dual jacks.   
      
     Has no effect on hum or noise coming from the tube.   
      
      
   > So you're right in saying that it has low impedence   
   > at the guitar pickup [which has its own issues with inductive coupling   
   > of hum, but that's a different issue]   
      
   ** No it isn't - cos it totally swamps the issue here.   
      
      FFS give up posting wild guesses as fact.   
      
      
   .... Phil   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)