[sdiy] XOR as 'digital' ring modulator
madhun2001 at yahoo.com
Thu Nov 11 00:09:41 CET 2010
Sorry, I was speaking theoretical so as not to confuse the reader with details.
A true diode ring mixer uses diode switching to reverse the polarity of the
carrier signal. Since it is a passive system, it has loss and not gain.
----- Original Message ----
From: Magnus Danielson <magnus at rubidium.dyndns.org>
To: synth-diy at dropmix.xs4all.nl
Sent: Wed, November 10, 2010 1:59:46 PM
Subject: Re: [sdiy] XOR as 'digital' ring modulator
On 11/10/2010 09:27 PM, Tim Ressel wrote:
> As a hopefully interesting side note, there are 2 ways to obtain the "ring
> modulator" function. The popular one for the synth crowd is a linear
> like the AD633. The other way is by polarity reversal. This is how true "ring
> modulators" work: the carrier signal goes through an amplifier that has a
> selectable gain of + or - 1. The modulation signal's sign determines the
> polarity: when the mod signal is positive the gain is +1, when negative, -1.
> This is of course not nearly as clean as the linear multiplier, but hey, clean
> is over-rated.
> The XOR ring mod works as a true ring mod, as an XOR gate is a
> digitally-controlled inverter.
> We return you now to your regularly scheduled programming.
No. The true ring mod does not have gain which shift between +1 and -1.
It has a gain shifting between those two extremes. A true ring mod
actually always have losses.
Modern ring-mod equivalents such as Gilbert cells can also be made to do
4-quadrature multiplications like the old double-balanced diode rings.
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