BASIC PRINCIPLES
A ring modulator is a device that combines two inputs (A and B)
into one output, transforming them into new sounds not originally heard at
the inputs. These are in fact the sum and difference of the frequencies of
the input signals (A+B and A-B). The original input signals are
suppressed, leaving the sum and difference signals to be heard together
as the output. This process yielding very complex waveforms can
produce many harmonies. This results in the atonal and “bell-like” effects
that are commonly associated with ring modulation (unless A and B are
harmonically related which has less atonal results). A special case (which
the String Ringer exploits) is when A and B are the same thus giving an
octave above (A+B). Low-pass filtering (i.e. removing harmonics from)
one or both inputs can greatly increase the purity of the output signal.
Most simple ring mod units have only one external input and produce a
tone (or “carrier”) to modulate it with. The carrier remains static (unless
manually tweaked) which greatly limits the effects possible. Modulating
the carrier frequency (i.e. moving it around a bit) hugely increases the
potential. String Ringer allows various ways to do this (by foot pedal, light,
external control voltage and not least the built in LFO- short for Low
Frequency Oscillator). The carrier (or “VCO” –short for Voltage Controlled
Oscillator) on the Ring Stinger also has an insert point allowing the carrier
to be overridden by a second external source as well as access to the
carrier itself which can be used as a sound source in its own right. It is
important to understand that a ring mod will produce a sound only if
BOTH inputs have sufficient signal going into them (the resulting output
level being a factor of both input levels). You can also use the insert point
to treat the carrier itself (e.g. with low-pass filtering as mentioned above,
gating, amplitude modulation etc.)
An ring modulator suffer from carrier breakthrough and distort
and degrade the original signal, especially those using a transformer/
diode matrix as in the String Ringer. However, by good design and time
consuming selection and matching of components the carrier rejection
achieved in other designs by using modulator chips has been equaled
and in most cases surpassed but with two distinct advantages: mega sex
tone and no periodical adjustment required. !
