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Phil Allison[_4_] Phil Allison[_4_] is offline
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Default Triode Naming Convention

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