In 2016, we pioneered an approach to reproduce and experiment with Web-based simulations of classical tube guitar amplifiers, initially the Marshall JCM800 used by many famous musicians (e.g. AC/DC). Our implementations run within standalone Web browsers. The different stages of the amps are perceptually approximated using simple tools from the WebAudio API (waveshapers, biquad filters and convolver nodes). This approach achieves enjoyable, fully playable and faithful re-creations or variations around the JCM800, that were positively assessed by objective measures (i.e. latency, time/frequency responses), subjectively praised by professional guitar players and academically well-received. Relying on the WebAudio API, despite the stringent constraints imposed by browsers (block processing, latency issues, thread priorities, etc.), this framework enables a quite worthwhile portability with minimal requirements (an internet connection and a Web browser on whatever device). In this chapter, we will detail this Web-based approach and give insights on how to reproduce faithfully and efficiently the typical distortions of tube-based guitar amplifiers. We will focus especially on the critical stages (pre-amp, power amp and output stage with negative feedback/presence loops) inside a fully versatile and modular framework, coined “Virtual Pedalboard” for the recreation of historic guitar amps and pedals from the Golden Age and the exploration of new designs.