Soundtoys Little Radiator Plug-in Analysis

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SOUNDTOYS LITTLE RADIATOR
LittleRadiator%20GUI

INTTRODUCTION
This is a follow-up ‘plug-in analysis’ from its bigger brother ‘Radiator’ that can be viewed here.
Little Radiator is not a simplified version of Radiator but modelled on a different Altec unit, the 1566A, whereas Radiator is based on the larger 1567A.

HARMONIC ANALYSIS
To analyse the non-linear behaviours of Little Radiator, I ran a 100 Hz sine wave through the plug-in at various settings. In addition, I passed Little Radiator through a Hammerstein module to trace the amplitude of the harmonics across the frequency range of the plug-in.

100 Hz sine wave at -12 dB passed through Little Radiator at Unity - Bias Disabled


Like Radiator, Little Radiator generates strong low-ordered harmonics. However, at this setting they are weighted towards the third. The third harmonic is associated with richness and depth.

100 Hz sine wave at -12 dB passed through Little Radiator at Unity - Bias Enabled


When Bias is engaged, Little Radiator generates stronger second ordered harmonics, the second harmonic adds body and is often associated with a warm and smooth sound. However, with Bias engaged, Little Radiator also generates stronger higher ordered harmonics. Higher ordered harmonics, especially above the seventh are particularly dissonant, and give a sound edge or bite.

100 Hz sine wave at -12 dB passed through Little Radiator at +6dB Heat - Bias Disabled


100 Hz sine wave at -12 dB passed through Little Radiator at +6dB Heat - Bias Engaged

Little Radiator at Unity with Bias Disabled passed through a Hammerstein module (4 Orders)


Little Radiator at +6dB Heat with Bias Disabled passed through a Hammerstein module (4 Orders)

Little Radiator at Unity with Bias Engaged passed through a Hammerstein module (4 Orders)

Little Radiator at +6dB Heat with Bias Engaged passed through a Hammerstein module (4 Orders)

It is interesting to see how the individual harmonics are affecting the sound. I only plotted the first 4 harmonics, as the graph gets a little convoluted when depicting additional harmonics.
Little Radiator’s lower-ordered harmonics are much more uniform to the fundamental when compared to Radiator, this will produce a cleaner and less dense sound.
Explanation : The Hammerstein module plots a trace per harmonic. The trace amplitude depicts the amplitude of the harmonic across the frequency range of the plug-in.

SOFT CLIPPING CHARACTERISTICS
For this test I ran a drum loop through Little Radiator at various settings. I have compensated for level so that the drum loop peaks at -1 dBFS for maximum resolution of the waveform in Pro-L. In addition, I passed a sine wave through Little Radiator at various settings and captured the results on an oscilloscope.

Drums – Radiator Disabled

Drums passed through Little Radiator at Unity - Bias Disabled


Drums passed through Little Radiator at +6dB Heat - Bias Disabled

Very nice transient rounding, sounds smooth!

Drums passed through Little Radiator at Unity - Bias Engaged

Drums passed through Little Radiator at +6dB Heat - Bias Engaged


Bias saturates higher frequencies more and produces a warmer but dirtier sound - very retro.

Oscilloscope - at Unity - Bias Disabled


Interestingly, compared to Radiator, Little Radiator produces smooth soft clipping behaviour on the negative portion of the waveform, more squared on the positive portion.
Little Radiator has asymmetrical soft-clipping behaviour.
Asymmetrical clipping saturates either the positive or negative portion of the waveform more then the other. This creates the generation of both even and odd ordered harmonics,

Oscilloscope - at +6dB Heat - Bias Disabled


Oscilloscope - at Unity - Bias Enabled

Oscilloscope - at +6dB Heat - Bias Enabled
LittleRadiator-Osc-Bias%206Heat
When Bias in enabled, Little Radiator also elongates the negative portion of the duty-cycle, which generates even ordered harmonics.

FREQUENCY AND PHASE RESPONSE
Frequency and phase response of Little Radiator at unity and then how particular settings change this relationship.

Frequency Response at Unity - Bias Disabled
LittleRadiator-Freq-Unity
Frequency Response at Unity - Bias Enabled
LittleRadiator-Freq-Bias
Frequency Response at +6dB Heat - Bias Disabled


Frequency Response at +6dB Heat - Bias Enabled

Phase Response at Unity - Bias Disabled


Phase Response at Unity - Bias Enabled

Phase Response at +6dB Heat - Bias Disabled

Phase Response at +6dB Heat - Bias Enabled

CONCLUSION
Little Radiator is a very different beast from its bigger brother with a different sound, espically when Bias is enabled. I know after this analysis I will be reaching for Little Radiator more often, especially on drum parallels in Bias mode for more grit.