line contact 44 to its open position shown in fig7 as working fluid flows downstream past the ball poppet 42 through the smaller diameter end 38 of the supply valve seat 36 consequently any sonic flow erosion damage caused by such initial flow of high pressure working fluid is shifted substantially immediately to an upstream area 45 of the supply valve seat 36 this is highly advantageous in that it shifts such wear or damage caused by such sonic flow erosion to an area of the supply valve seat 36 that is adjacent to the annular space 43 rather than in contact with ball poppet 42 accordingly the sonic damage to the smaller diameter downstream sealing end 38 of the supply valve seat 36 is minimized as a result the damage to and wear of the actual sealing surface of the valve seat 36 on the ball poppet 42 is likewise substantially minimized and the functional life of the exemplary control valve 10 is correspondingly greatly extended in this regard the downtime and the maintenance costs are reduced for a system employing a control valve 10 according to the present invention as will be readily recognized by one skilled in the art the above described function of the ball poppet 42 with respect to the supply valve seat 36 as shown in fig6 and fig7 is similar to that of the function and relationship of the exhaust ball poppet 52 and exhaust valve seat 46 referring primarily to fig8.