Grid stopper resistor question

[sumotan]

Hi Tweaker
Re image Ac in / Ac out = AC waveform, analog signals are in this form.

 

[Tweaker898]

"Btw as resistor value goes up the apperant inductance goes down." Semper, this seems exactly backwards for a film resistor that is spiral cut. The inductance will go up with resistance value.

 

[Tweaker898]

"The thermal noise (Johnson or Nyquist) is exact the same for any resistor tupe. It is only a factor of the resistance value." Well Semper, I don't think that is exactly true. For example different resistors of different mechanical construction and wattage will heat and cool at different rates effecting Johnson noise, correct?

 

[Tweaker898]

Gee, I thought so Sumotan. AC means alternating CURRENT. Small amount that it is. If the audio AC signal doesn't go through the grid stopper I do not understand it at the present time. Hopefully soon I will compare the carbon film that's in the unit to a metal foil in the grid stopper position to see if my golden ears can perceive what some believe would be a hallucination because of what some say is near zero voltage and current.

 

[OldHector]

I'm making a tube socket adapter so I can try some Loctal tubes in Octal sockets. One of the tubes is similar to a 6V6GT, and the other is similar to a KT66. The adapters are made by pushing wires from the relevant pins of an Loctal socket through the pins of an unused tube base, gluing the two together (to minimise the wire lengths) then soldering in the pins.
Do I need to consider fixing a grid stopper inside the adapter, so it is attached to the Loctal control grid pin, or is it OK to rely on the grid stopper that would be installed for the original Octal tube, on the Octal base below the adapter?

 

[SemperFi]

"The thermal noise (Johnson or Nyquist) is exact the same for any resistor tupe. It is only a factor of the resistance value." Well Semper, I don't think that is exactly true. For example different resistors of different mechanical construction and wattage will heat and cool at different rates effecting Johnson noise, correct?

The noise u are thinking about is 'excess' or current noise. Thermal (aka johnson and nyquist) is purely resistance no matter the type of resistor, or impedance of the ocean, outer space, whatever.

 

[SemperFi]

"Btw as resistor value goes up the apperant inductance goes down." Semper, this seems exactly backwards for a film resistor that is spiral cut. The inductance will go up with resistance value.

No b/c u need seriously huge inductance to dominate housand ohms even at 100kHz... The capacitance on the otherhand will become noticably when the resistance is high even below 1MHz if the resistance is high enough.
Parasitics are always relative to what is in series or parallel to them.

 

[SemperFi]

Vishay has some decent graphs showing R/frequency in their data sheets and u can see that generally the further below 100ohms inductance dominates and the further above 100ohms capacitance dominates.