DC-Cascaded Amplifier
    The next possible circuit for the first stage is the cascaded amplifier. Here one grounded-cathode amplifier cascades into another. In the schematic below, the connection is capacitor free, i.e. DC coupled. Each triode sees the same cathode-to-plate voltage, with resistor R taking up slack voltage. This circuit yields a huge gain that would be suitable for MC cartridge use.

    Tube CAD does the hard math for you. This program covers 13 types of tube circuits, each one divided into four variations: 52 circuits in all. Tube CAD calculates the noteworthy results, such as gain, phase, output impedance, low frequency cutoff, PSRR, bias voltage, plate and load resistor heat dissipations. Which tube gives the most gain? Tube CAD's scenario comparison feature shows which tube wins.

Grounded-Grid Amplifier
   The grounded-grid amplifier does not invert the signal's phase at its output and it offers a low input impedance, as the input is the cathode rather than the grid. A low input impedance (100-600 ohms) is great for MC cartridges, but not so great for MM cartridges, which prefer to see an impedance between 10k to 47k.
    Since the cathode is the input of this circuit, DC coupling becomes difficult, as ground-level DC coupling would require using a negative power supply and a negative grid voltage to place the cathode at 0 volts. A DC servo loop would help, but the cartridge would still be susceptible to damage at turn on, when the tube just starts to conduct and the servo might be too slow to prevent a large DC offset at the cathode. Consequently, a coupling capacitor is the safer approach.

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