Conrad-Johnson PV-5 preamplifier
Tubed preamplifiers have a well-earned reputation as system busters. Many of them during warmup produce horrendous bangs or plops so severe that every speaker fuse in the system blows. If fuses are absent, or rated too high to protect things, the amplifier, speakers, or both are likely to blow up (not literally; they just twitch once and lie down dead). The PV-5 contains one of the most effective pop suppressors I've encountered, and produces no noise whatsoever during warmups and turnoffs.