[78-L] PItch change

Steven C. Barr stevenc at interlinks.net
Thu Dec 31 20:29:58 PST 2009


----- Original Message ----- 
From: "DAVID BURNHAM" <burnhamd at rogers.com>
>I don't usually quote from such a long letter but this issue was discussed 
>over a week ago and any comments I make won't make any sense without the 
>comment which inspired the response.
> I found this posting a little disturbing because it demonstrated some 
> rather narrow thinking on the part of someone who obviously has a broad 
> understanding of his specialty.
>
Point being...virtually ALL of us on the 78-L list are used to the 
(supposedly) "warm"
sound of analog recording...! As I have often posted, there is a technical 
reason
behind this...! When a vacuum-tube amplifier is overdriven, it reaches 
"cutoff"
gradually. The output waveform starts as (fairly) perfect sine waves...but 
as the
tube reaches "cutoff" the sine waves lose their "top end"...but NOT all at 
once!

If the input is a series of perfect sine waves, the "overdriven" output will 
be a
series of unmatched sine waves! OTOH, an overdriven solid-state amplifier
simply amplifies up to "cutoff" and then ceases. The result is a series of
sine waves with perfectly-flattened tops...the functional equivalent of
square waves! Square waves have a nasty sound when fed into an audio
amplifier; however, the gradually-distorted waves produced ny vacuum-
tube amplifiers do NOT!

Steven C. Barr 




More information about the 78-L mailing list