There is so much misinformation on this page that I thought I might add some technical information.This Yellow Jacket semiconductor rectifier is composed of standard solid state diodes. Now, solid state diodes come in many different types, obviously, since they come in different voltage and current ratings, but also, more important, different material of composition. Standard solid state diodes suffer from turn on and turn off noise and so new types of diodes were invented to mitigate the noise. These are the high speed fast recovery diodes such as the Schottky diode. These Yellow Jacket replacements are composed of the noisy p n junction silicone diode. Those who do it yourself (a very simple job) would use the Schottky diodes and the two diodes would cost about $20; so you can see why they are not used in the Yellow Jacket.There is considerable confusion about power supply sag. Any power supply has internal resistance. The power transformer itself has resistance in both the primary and secondary windings. Any competent supply (but not necessarily a guitar amp PS) will have a Pi filter composed of a capacitor, inductor, and capacitor. The inductor has a certain resistance that adds to the internal resistance of the power supply too, but it is very effective at eliminating much of the hum. Cheaper power supplies use a resistor instead that, obviously, add resistance to the supply increasing its internal impedance.The sag is simply a function of the internal impedance of the power supply. As more current is drawn from the supply under loud passages or power chords, the internal resistance of the supply drops more voltage: Ohm's law at work! So the higher the impedance of the power supply, the more voltage is dropped; it is that simple. Solid state diodes have a lower resistance than a tube rectifier and, in the same amp, this will increase the power supply voltage.As an example, if we have an amplifier that pulls 300mA from the power supply at idle, Ohm's law tells us that, if the power supply has an internal impedance of 200ohms, it will drop .3 x 200 = 60 volts. If we have a loud passage and 350mA is drawn from the PS, it will drop .35 x 200 = 70Volts. The power supply voltage has dropped by 10V. That is power supply sag!