London Power’s SL-MV Splitter-Limit Master Volume is an improvement of an old idea that needed improving!
Techs and amp designers have used various methods to control the gain of the Schmitt splitter to affect output level. In all these cases, the current through the splitter has been varied, because this parameter affects the available drive to the power tubes.
These usual methods are compromises. They can introduce scratchy sounds and even speaker “earthquakes” as the control is manipulated. Why are these approaches used? Often, the player simply wants something different – an alternative to traditional master volumes. Sometimes the choice is purely aesthetic – the designer or player does not want a master volume, because the old-style MVs were known to alter tone.
These common splitter-control approaches are a way to side-step the master-volume issues while achieving the same goal.
Our SL-MV Splitter-Limit Master Volume achieves this goal without the sonic detriment.
SL-MV allows the player to control the splitter gain and output via a front-panel control. A small PCB carries the pot plus the three components left out by everyone else – the ones essential to smooth operation. The SL-MV provides a wider range of loudness control than do the intuitive traditional wirings.
This type of control has variously been called “Limit”, “Power”, “Variac”, “Watts”, “power dampening” etc., but please be aware that the benefits to the amp are not as far-reaching as some marketers would like you to believe. Tube life is NOT extended (this is explained in our book The Ultimate Tone Vol. 4 (TUT4). Only properly implemented Power Scaling will extend tube life.
The SL-MV comes with helpful notes including installation tips and schematic diagrams of the kit.