[sdiy] passive ring modulator transformers

[Neil Johnson]

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