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Message

Re: Ring vs. Balanced Modulation

2008-12-31 by zaum

Reading the website description, clearly a ring modulator is a subset  
of a balanced modulator's range.

Allen Strange discusses it in the context of Audio Rate AM and the  
original 285 module.

"Most balanced modulators must have a manual and/or voltage  
controlled "modulation" index. If the modulator is designated as  
completely balanced, the term "index" is irrelevant as index is  
always at maximum.
As discovered with AM, the index controls the magnitude of the  
sidebands."

He mentions the two outputs sets on the original 285, one is VC going  
from no modulation (zero) to full balanced (ring) and the second is  
only ring modulation independent of the variable modulation index.

"Therefore an instrument labeled "balanced modulator' will provide  
different degrees of carrier suppression"

"With complete balanced modulation there is no need to distinguish  
between "carrier" and "program". (signal and ref on the Buchla)

Also perhaps of interest, though I don't know the if the 285 or 285e  
is AC coupled, the point is made that without AC coupling any DC  
offset on an input will add the DC amplitude of the offset frequency  
to the output (which would have been suppressed had the signal lacked  
DC offset)

nick

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