An OPV can, therefore, be thought of as an attempt to fine tune the amount of resistance being overcome in a hydraulic system. The primary job of producing resistance in an HX espresso machine is performed by a Pressurestat, which governs (via pressure) energizing a heating element through a manipulation of a SPDT (Single Pole Double Throw) switch, to heat the water within a HX Boiler System's Steam Boiler, which in turn transmits this hydraulic system overall resistance passively to the HX Thermosiphon loop via kinetic energy transfer between the heated water/gas molecules in the steam boiler and the HX Tube's metal surface. Unfortunately, control of an HX espresso machines Steam Boiler pressure is usually not easy to get at and often requires disassembly of the machine's casing to some degree to reach the Pressurestat adjustment screw. Once a Pressurestat is adjusted (calibrated) to produce the proper pressure in the HX espresso machine's Steam Boiler corresponding to a specific extraction temperature (correct for a specific roast light to dark or somewhere in between) for an optimal grind and tamp, there will be no need to adjust the machine further. An OPV offers similar control but instead of regulating kinetic energy transfer between the Steam Boiler and HX-Line, the OPV attempts to directly regulate the amount of resistance being overcome in the HX Hydraulic Line.
Neither method of adjusting the extraction temperature target is perfect, but both have their advantages and disadvantages. The most important thing to keep in mind is that these variables can change over time (resulting in increases or decreases in amount of resistance in the hydraulic system), depending on mineral buildups in a machine, components wearing out or failing, and other factors that make it tough to rely on a specific Presurestat or OPV setting. Moreover, if a person changes their roast suddenly from a light roast to an espresso dark roast, the extraction temperature change required in the espresso machine is 10℃ and expecting to get the same quality of organics extraction from similar tamping/grinding in a dark roast as from a light roast calibrated espresso machine is not possible. And so, we often see, as above, people instinctively attempting finer grinding, increased tamping pressures, adding extra components such as OPV's, gigleurs and many other items, which can be very effective, but in reality, the design of the Nuova Simonelli Oscars and Musica is of such a quality and specification that all that is needed is to adjust (calibrate) the pressurestat on these machines to correspond to the lightness or darkness of the roast, between 92 ℃ for light roast, preferred in Europe, Northern Itally and North America, and 102 ℃ for dark roast as preferred in Southern Italy etc. The Nuova Simonelli Oscars and Musica's are of such a design quality that all that is needed is this pressurestat calibration to produce perfect extractions.
Some folks like to diss the Oscar and Musica espresso machines, and this is understandable if they own an different espresso machine. However, the Oscars I and II in particular are amongst the best espresso machines ever invented and manufactured, by any company . . . incredible feats of engineering genius and technological design that rival and equal any espresso machine, including the latest and greatest machines. Indeed, many machines derive numerous features from the patents developed for the Oscars. These new espresso machines are indeed mighty and impressive, but the Nuova Simonelli Oscars and Musica's rival them in every way and stand shoulder-to-shoulder with them as their equal partners in the very impressive field of incredible machines we all have come to enjoy and admire in the coffee culture and communities we share here and in coffee shops throughout the world

Leave a comment: