[R-390] 60 Hz HUM Why AC filiments?

[Barry]

From: "Rasputin Novgorod" <priapulus at yahoo.com>
> I must confess that I don't have a lot of experience
> with tubes; But pumping AC into a tube seems to me
> to be a great way to inject hum. Why did they do it?
>
> Given how cheap and easy diode rectifiers and regulators
> are today, should we convert AC filaments to DC?
>
> Sincerely
> /b

Ras,

The HP-606A uses a rectified and well-filtered supply for the RF tubes.  I 
was kind of surprised to see that.

Good to hear from you,

Barry - N4BUQ