<https://www.head-case.org/forums/topic/10783-megatron-electrostatic-headphone-amplifier/page/34/#comment-814982>
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"Has anyone continued to investigate something about preamp tubes?  \n \n\n\n\tI still use the E180CC instead of the 12AU7.\n \n\n\n\t \n \n\n\n\t \n "
<https://www.head-case.org/forums/topic/10783-megatron-electrostatic-headphone-amplifier/page/34/?tab=comments>