Mod - Adding a PPIMV Master Volume in Essex
PPIMV – (Post Phase Invert Master Volume) For valve amplifiers without a master volume this is by far the best kind of master volume modification around, tonally it provides very little colouration while allowing you to crank the preamp valves.
Important to point out though that it doesn’t overdrive the power tubes unless up loud so the distortion will be far different than using other devices such as speaker load attenuators. This is a popular mod to carry out to older Marshalls or amplifiers which only have a single gain control.
There are quite a few ways to add a volume control, from a simple variable resistor in the send / return line however these can change the sound as they change the impedance of the signal going through the chain.
Adding a PPIMV control is fairly straight forward, it needs a hole to put the extra volume control, generally a spare speaker socket is removed and this hole used to avoid drilling any more holes or to revert the amp back pre mod if required. Despite being fairly straight forward we have seen so many wired incorrectly which will negatively affect the sound especially at low volume, or controls fitted with the wrong fade taper meaning for 80% of the travel the control does nothing, then in the last 20% the amp is silent to full volume which makes it a quite fickle control if incorrectly fitted.
If you are interested in having this fitted please use our new repair enquiry to get in touch and let us know the amp you have, as it’s easier on some amps than others and may not be suitable for all designs.