artificial centre tap

[jestaudio]

Used one recently on a champ build but am wondering is there any particular reason for using 100r resistors as oppsed to say 120r or a maybe 80r, how much leeway is there,ive had a look on the web before asking but there does,nt seem to be a definitive answer(plus i have stacks of 120r resistors waiting for use )

[martin manning]

Typically something in the 100-200 ohm range is used, so 120 ohm will work fine. Lower values will work too, but unecessarily increase the load on the filament winding.

[jestaudio]

Typically something in the 100-200 ohm range is used, so 120 ohm will work fine. Lower values will work too, but unecessarily increase the load on the filament winding.

Got loads in that range, i,ll probaly use 180 ish as load could become a concern

[pdf64]

I see a benefit in using high wattage types, say 3 watts or more. In order to maintain a solid ground reference for the heaters in the event of a tube short.
If a tube failure is able to pull all the heaters to a high voltage, the heater to cathode insulation of all the tubes in the amp may get damaged.
It's quite common to find the standard 100 ohm 1/2 watt blown; I can't think what could cause that to happen other than a tube failure which allowed B+ current into the heater circuit.
Pete.