[sdiy] XOR as 'digital' ring modulator

[cheater cheater]

Magnus,
I'm afraid I didn't understand what you said there. Could you elaborate please?

Thanks
D.

On 10/11/2010, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 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
>> multiplier
>> 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
>> gain
>> 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.
>
> Cheers,
> Magnus
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