We started with the GEC ECC83 and some SPICE models to get the essential anode load characteristic of our preamp valve. From here we went on to add detailed characteristics for cathode and grid circuits. Once our model was behaving just like a real ECC83, we took the algorithm and re-implemented it in a more efficient format for use in our amp designs.
Next we built a library of passive filters that would form the interconnecting circuitry between preamp stages, carefully transposing the classic guitar amp circuits into corresponding digital filters and ensuring the correct interaction between tube stages and connecting circuitry.
For a more insight into our modelling techniques, see the article 'Vitrual Amps for Rookies' on SoundBytesMag.
Dynamic Power Amp
For a really natural tube amp feel, a dynamic power amp stage is the critical ingredient. Our solution reproduces the subtle compression, clipping and frequency response of a real tube power amp. We deal with the harmonic effect of power supply sag, clipping and shift in high frequency response, all determined with dynamic parameters reacting to how hard the amp is driven.
Each S-Gear amp includes an 'Amp Drive' parameter and a 'Tweak' panel. The Amp Drive pushes the power amp harder and increases the dynamic effects. The Tweak panel lets you fine tune Power Supply Sag, High Frequency Cut and Presence Frequency. Dial up the power amp tone and feel, just as you like it.