Filament coil without c.t.

[Deepdark]

When We have a filament coil which doesn't have a c.t., it means the coil is 6,3v-0v, isn't it? By creating an artificial one with a pair of 100r to ground, does it force the coil to be 3,15v-3,15v? So We strap tubes like 12ax7 the common manner, pin 4-5 and 9, is that it?

 

[CJ]

yes, strap 4-5, connect to one green wire,  connect 9 to the other,
100 ohm virtual CT is very common,

more circuits here>

http://groupdiy.com/index.php?topic=57166.msg728663#msg728663

 

[PRR]

> the coil is 6,3v-0v, isn't it?

There's no "zero" on a winding.

When you test it on a bench, you pick one lead, *call* it "zero", and measure the other lead(s) *relative* to that. 0-6V.

Yes, when you connect a symmetrical network *across* the winding, and call that mid-point "zero", now you will find half-voltage on either side. 3-0-3V.

> strap tubes like 12ax7

The tube does not have an internal "zero" either. As long as one leg is 6V apart form the other leg, it heats.

 

[Deepdark]

Thanks guys. I've read some data sheet from edcor recalling one lead 0v or common, while no c.t. Which gave, ie, 5v-0v or 5v-common. Common should be a better way for naming it i guess