[Amps] Filament Voltage Question

[Bill Turner]

ORIGINAL MESSAGE:          (may be snipped)

On 4/22/2014 9:09 AM, Jim Garland wrote:
> Hum rejection (also pointed out
> by a commenter) would seem to me to be worse in low V/high I filaments,
> since the induced hum field would be greater.

REPLY:

There is another issue too: With a directly heated cathode (filament), 
there is an unintentional bias across the filament. Whether using AC or 
DC, one end of the filament will be more negative than the other and 
that adds a grid-cathode bias to the equation. With DC the bias is 
constant, with AC it alternates of course. More anode current will be 
emitted from the negative end and less from the positive end.

I don't know if this causes any actual harm, but I can't imagine it 
helping any.

73, Bill W6WRT