I have seen so many statements about " I think I blew up my amp because I engaged in an unusual action where I." to think that black-swan events cannot ever happen, because they do. We're made out of meat and meat is a bad substrate for computation, and even worse for repetitive procedures, even when OCD is in play. We may also not notice a wire has been pulled out, such as during vacuuming. Humans are very poor at always following procedures which are not written down, particularly when distracted. The "this could never happen" because of "always" following a checklist of verifying speaker connections is a misguided argument. I've elsewhere posted links to safety cautions about the MOV and fires resulting from same.) This is why the MOV must never be used in a socket strip. Each conduction burns a lower impedance path through the device. (An MOV is totally unsuitable as it has very limited number of cycles before it fails as a short. (b) Augment (a) with a TVS diode, acting much like a zener, across the primary and from each winding to the center-tap so as to conduct at the appropriate threshold and safely dissipate the energy. The standard values are generally selected to be sufficiently high so as to: So no distortion would accrue in normal operation. The superior alternative to the resistor is adding a flyback diode, which only conducts when inductive flyback is generated. I doubt anyone could hear the difference. But since speakers are nominal, anyway, that's not significant. If one had 470 Ω and the speaker is 8 Ω the resulting impedance is 7.87 Ω. The value the resistor, however, matters, and the import is greater than merely wasting a small amount of power a small alteration in output impedance also occurs. This approach is widely used in guitar amplifiers, as it is not uncommon for speakers to be not connected, shut off using switches, or accidentally disconnected during use.īoth resistors and diodes may be simultaneously used as belt and suspenders. Adding flyback diodes is a superior approach for a variety of reasons, particularly that a breakdown voltage of the TVS need not be exceeded, and the clamp works as soon as the voltage climbs above supply in exactly the way that diodes routinely function. This is why socket strips with MOVs occasionally start fires in homes and businesses. An MOV is not suitable as it degrades with use, as the repeated breakdown causes low-resistance paths to be permanently created through the grains, which eventually turns into a dead short. This is a standard approach.Īnother, and less common, solution is to place flyback diodes or TVS diodes across the output transformer, as these will harmlessly divert any inductive kick once the voltage rises. I think it adequately addresses a reasonable solution to the issue at hand.Īs a protective measure one may place a high-value resistor, say 470 Ω, across the output transformer's terminals such that the high-value dummy load is placed in parallel with the normal 8 Ω load and the parallel resistance thus does not materially affect normal operation. Since I have been asked, here is some information I've previously posted, and some which I've sent via PM after in inquiry, loosely edited together.
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