 When people think about guitar tone many people think about valves and of course our St. James amps use these in both the preamp and the power amp but surrounding valves are hundreds of other components and other important circuits. Of these the power supply feeding the valves has a crucial role in how an amplifier works and produces sound. Even though the actual signal does not pass through the power supply it's responsible for the amplifier's headroom, how much noise is introduced into the system as well as its dynamic response to transients. In more musical terms the attack of the note or chord. Up until the release of St. James Blackstar valve guitar amplifiers and almost all others have used traditional power supply methods using big heavy transformers. Today we're going to talk about an alternative form of power supply that we developed at Blackstar for high voltage guitar amplifiers using SNPS technology switch mode power supply. But first why do we want to move away from traditional power supply methods? A traditional power supply usually called a linear supply basically consists of three main elements a transformer rectification diodes and smoothing capacitors. These convert the AC main supply into a DC voltage. This is very simple but it is also very inefficient. This results in the transformer itself basically a lump of iron and copper needing to be fairly large and heavy. This makes the whole product heavy. Also to perform well in audio circuits linear supplies need extra circuitry to smooth the voltages to reduce mains hum from being too audible. Other common issues with linear supplies is that their output voltages vary with changes in actual local mains supply voltage. This can result in inconsistencies in tone and they need to be rewired or even have a different transformer for territories with vastly different mains voltages such as Europe and America. Alternatively a switch mode power supply is inherently more efficient. It still has a transformer but due to the high speed switch mode design it's about three times more efficient. This free fold increase in efficiency means that the transformer the main weight in the whole amp can be about a third of the size and weight as a linear supply. So this is not an incremental difference it's a big difference. The fact that the mains frequency content is removed in this high speed switching also results in hum being effectively eliminated from the supply outputs. This leads to lower noise and hum more stable biasing which itself leads to more consistent tone from venue to venue. Our SNPS can also accept all international mains input voltages. So the same amp can be used in London, New York, Paris and Tokyo without any electronic changes and again with completely consistent tone. Now switch mode power supplies themselves are not a new thing. Due to the desire for efficiency and lightweight products elsewhere switch mode power supplies are now found in almost all other consumer applications. Computers, laptop adapters, phone chargers, flat screen TVs, pedal supplies, etc. are already generally using them. However these are usually quite simple supplies with often just one voltage output. In our case a modern valve guitar amp usually needs four or five voltages to power the different elements including a high current supply to heat the valves and around 460 volts for the main high voltage for the power valves. This means that an SNPS for a valve guitar amp is not a simple off the shelf device. So we had to develop this ourselves. The demanding nature of a valve guitar amp resulted in many challenges needing to be overcome before we were happy that these performed as robustly as a simple linear supply. Before we finish I should just make a few things clear. SNPS should not be thought of as a digital supply. That term is completely inaccurate nor is it in any way a compromise. These provide the same voltages and currents to the audio circuits as a linear supply. The main signal path from St James outfires from input to speaker is completely analog. The only digital sections are the custom voice reverb and the awesome groundbreaking cab rig DSP technology both of which have been developed by our world-class in-house digital team. We believe that our development of the SNPS in the St James products along with cab rig DSP driven by clever power reduction technology and an inbuilt reactive load represents a big step forward in the world of catamplification solidifies St James as the most advanced valve amp in the world and for a 50 watt model the lightest.