[sdiy] passive ring modulator transformers

[Simon Brouwer]

Hi Neil,
 
The transformer-diode ring modulator is not "just a switching modulator", it is
sort of half way between a true switching modulator and a product modulator, as
the diodes are operated in the area where they are not fully on or off.
It should be no coincidence that germanium diodes are preferred in this circuit,
as they have a softer current-voltage knee.
 
Best regards
Simon
 
 
> Op 17 januari 2016 om 15:10 schreef Neil Johnson <neil.johnson71 at gmail.com>:
>
>
> Hi,
>
> Simon Brouwer wrote:
> > I imagine a big part of the sonic difference between the
> > transformer-and-diode-ring modulator and analog-multiplier circuits is the
> > nonlinear behaviour of the diode ring.
>
> A ring modulator is just a type of switching modulator - only the sign
> of the carrier is important, and the sharper the switching edges the
> cleaner the resulting output.
>
> Whereas the analogue-multiplier circuits are in the class called
> product modulators.
>
> There are many different ways of making switching modulators. The
> original advantage of the diode ring and transformers was cost - in
> 1934 "op-amps" didn't really exist, and diode choices were either
> thermionic or copper-oxide.
> You can kind-of emulate a switching modulator with a product modulator
> by driving the carrier input with a square wave.
>
> > If the transformers do not contribute a lot of distortion (assuming that in
> > this application they are not driven to saturation), they might be replaced
> > by opamp circuits without losing much of the characteristic sound.
>
> You can make a switching modulator with a single op-amp and a transistor.
>
> Cheers,
> Neil
> --
> http://www.njohnson.co.uk
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