Tubescreamer simulation under PSpice

Just for fun, here is a PSpice simulation of an Ibanez Tubescreamer.

Simplified schematic used to simulate :

Tubescreamer PSpice SchematicNote : Drive and tone pots are represented as resistor. More convenient under PSpice as pots are not implemented (to my knowledge, maybe I’m wrong)

Bandwidth : (note the 700hz mid-hump)

Tubescreamer PSpice Bandwidth

Wave forms :

Tubescreamer PSpice WaveFormInput on top, output at bottom. The waveform at the output (“shark” ;-) ) essentially because of the 220nF capacitor. One test is to remove it, you should obtain a more “squared” waves …

How to add post clipping boost (not more distortion but more volume)

Notice resistor R9 of 1kΩ. Let’s say we replace it with a 100kΩ (for instance, a log variable resistor, I assume) ; it could be done with a spdt switch to choose between 1k (standard tubescreamer resistor) and 47k to 100k with the variable resistor for a boost from 8 to 14dB …

Tubescreamer PSpice Schematic Post clipping boostHere is the difference between 1k (green) resistor and 100k resistor (red) :

Tubescreamer PSpice Bandwidth boost post clipping

Of course, these are PSpice simulations, to be prototyped.

When prototyped, we learn that R9 too high means a lot of parasitic oscillations, when highs are pushed to the max (and a lot of distorsion when high pot turned full clockwise !). In practice, 2k seems to be a good value for R9, not more.

Have fun !

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