Amp Module: Power Amp


Power Amp



The power amp topology plays an important role in shaping the dynamic characteristics of the power amp’s tone. It defines at what point the power amp will start to break up, and how it will break up. It might sound subtle, depending on different parameter settings, but you will certainly find the sonic differences to be just like those for the real power amps’ responses.

Single Ended

Models the Class A single-ended amplifier. A single-ended-triode vacuum tube amplifier uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output. When going into distortion, it generates a uniquely abrupt distortion.


Models the Class A/B push-pull amplifier with a split-load (also known as “concertina”) phase splitter. Its special topology creates the most smooth and rich power amp distortion.


Models the Class A/B push pull amplifier with a long-tail pair phase splitter. The long-tail pair phase inverter is generally the best choice for a push-pull guitar amplifier. It provides balanced and warm power amp gain structure and very workable headroom.

Solid State

Models solid-state power amplifiers, which use transistors (such as BJTs, FETs and MOSFETs). It creates the cleanest tone possible, with much less distortion than other types of amps. Your ticket for pure and clean tone.


The MASTER KNOB was originally designed to simply control the input signal driving the power amplifier. But since the power amplifier is a highly dynamic beast, it’s no surprise there is much more to it than just loudness control.

The MASTER KNOB provides one way to control how much power amp distortion you would like for your amp, as it defines the breakup of the power amp distortion. By working with the preamp GAIN KNOB, you can manage the balance of preamp distortion and power amp distortion.

When the power amp section gets heavily saturated, the EQ controls, tone stack controls and presence control will have less influence on the tone and the sound will have a more “boomy” effect.


The DISTORTION KNOB is an extra control for adjusting the amount of distortion in the power amp tube stages. It provides greater resolution to allow fine-tuning the distortion—the break-up point—to match that in various amp designs.


The SPLITTER GAIN knob adjusts the distortion in the phase-splitter tube stage. Use this knob to fine-tune the distortion characteristics just for the phase splitter.


The POWER GAIN KNOB adjusts the distortion in the output tube stage. Use this knob to fine-tune the distortion characteristics just for the output tube stages.


This control sets the bias operation point of the power amp. Lower values will create less power amp harmonics, while higher values will create more dynamic harmonics. 


The PRESENCE knob boosts or cuts upper frequencies in the power amp stage by altering the negative feedback’s frequency response.

MODERN mode creates a sound that cuts more through effects, especially with higher-gain amp types. VINTAGE mode delivers a more classic and balanced upper range. 


Guitar speakers have an interesting impedance curve shape, which typically has a peak at about 100 Hz and rises gradually above 1 kHz. The speakers interact with the power amplifier through the transformer. The RESONATE knob controls the resulting effect in the lower and upper frequencies. The effect is different depending on the selected power amp tube types and transformer type.

The PUSH switch mode delivers an effect that helps the guitar tone cut through a mix, whereas NORMAL mode replicates a more balanced interaction between power amp and speakers.


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