Bipolar Junciton Transistor modelling for Virtual Analogue

Rangemaster comparison

To further understand the Rangemaster in a real scenario, here guitar signals are compared. The signal is a chord normalised to have a peak value of 1 V. The signal is then processed at 8x oversampling through the Rangemaster for the three models: Ebers-Moll (EM), DC Gummel-Poon (GP), and AC Gummel-Poon. The waveforms are displayed below:

Sound examples

The three BJT models in the Rangemaster are here compared through sound examples in the below table. The input signal used is a direct recording of a guitar (Gibson Les Paul Junior, P90 pickup) featuring strumming and arpeggiation of some chords. An amp simulation follows the Rangemaster for one set of signals to better represent the a useful sound of the effect. The amp sim used was “Brit and Clean” from GarageBand which, based on the representative image in the software, looks remarkably like a Vox AC30.

A noteable difference between Ebers-Moll and Gummel-Poon can be heard in the transients of the arpeggios, particularly noticeable on the signals without amp simulation

	Dry	Ebers-Moll	DC Gummel-Poon	AC Gummel-Poon
Guitar -> Rangemaster
Guitar -> Rangemaster -> Amp Sim