I believe the Hallicrafters used several pairs of lightly coupled tuned
circuits. The 1960s receiver, a GEC RC411, had crystal filters.
There is of course another advantage to the thermionic device. It is more
robust than a large number of transistors. One of my colleagues described
the power transistor as "the fastest fuse known to man".
John Rabson
----- Original Message -----
From: "Alberto di Bene" <[email protected]>
To: <[email protected]>
Sent: Tuesday, October 22, 2002 3:19 PM
Subject: LF: Re: Vacuum tubes on Motherboards...
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
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