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-   -   Filament Transformer Question ? (http://www.diyaudio.com/forums/tubes-valves/232009-filament-transformer-question.html)

HP8903B 14th March 2013 01:27 AM

Filament Transformer Question ?
 
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Eli Duttman 14th March 2013 01:35 AM

2X "6" V. tubes of the same type and same production run, with their heaters in series, will be fine connected to the toroid. You could bias the junction point of the 2 heaters off B+, for noise control.

HP8903B 14th March 2013 01:37 AM

Quote:

You could bias the junction point of the 2 heaters off B+, for noise control.
I don't understand this

FoMoCo 14th March 2013 01:52 AM

Quote:

Originally Posted by manp111 (Post 3409820)
I don't understand this

Take the center connection of the two heaters, the two that you connected together and are not connected to the transformer, and place about 50V of bias using a resistor divider from B+. It's not a requirement, but can reduce hum.

HP8903B 14th March 2013 01:54 AM

What about connecting the center connection (center of two filaments) to ground ?

Bibliophile 14th March 2013 02:53 AM

You can ground the centre point but, if it is a high gain circuit such as an MM or MC preamplifier, elevating the filament can yield a useful reduction in hum as previous posters have said.

HP8903B 14th March 2013 03:05 AM

Thank you guys

Eli Duttman 14th March 2013 03:14 AM

Quote:

What about connecting the center connection (center of two filaments) to ground ?
In addition to biasing that point off B+ with a resistive voltage divider, you ground that point via an electrolytic cap. of several μF. As the other posters stated, the network of 2 resistors and 1 cap. reduces vulnerability to hum and other noise.

FoMoCo 14th March 2013 11:46 AM

Quote:

Originally Posted by Eli Duttman (Post 3409918)
... you ground that point via an electrolytic cap. of several μF. ...

+1 on the cap.
If you want, you can calculate its value based on the resistance. But, I'd probably just make it 10uF and be done with it.


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