LF: Re: Vacuum tubes on Motherboards...

["Alberto di Bene" <dibene@usa.net>]

John Rabson wrote:

> A few years ago, I was restoring an ancient Hallicrafters receiver and
> noticed the crisp quality of the audio compared with that of a 1960s
> transistorised communications receiver. I spoke to one of the experts at BT
> Labs, who suggested that the output transformer might have something to do
> with it. Also, the characteristics of a bipolar transistor audio output
> stage are _not_ identical to those of a pentode or beam tetrode.
>
>  
IMHO, the main reason for the more pleasant sound is the IF 
filter...supposing the '60s receiver
uses a crystal filter, while the Hallicrafters not.
Crystal filters are wonderful in the frequency domain, but terrible 
performer in the time domain,
while LC filter just the opposite...

73  Alberto  I2PHD