We can’t let it supersede our knowledge of the amplifier’s circuit or whatever other evidence the amp is offering. Although we can and should listen to it, we can’t let it dictate our method of troubleshooting. Likewise, the noise floor is an unreliable witness.

In order to make sense of the green hat as evidence, you ideally need other information from other sources as well.

So, you can’t simply arrest the first person you see who is wearing a green hat. Think of it this way: if you are the detective, the noise floor is the witness that says, “A guy wearing a green hat robbed me.” This is a great piece of information as long as you don’t forget that 1) a lot of people own green hats 2) people have the ability to take their hats off, and/or put new hats on 3) a lot of people don’t know what the color green is (Is chartreuse green? Is teal green?) 4) if the witness was dishonest or forgetful, there might not even be a green hat in the first place. The more you listen to the amp and think about its issues, the less you’ll rip out and replace perfectly good components and drive yourself to total frustration. However, the point is that everything that the amp is doing should be treated as evidence of its malfunction. We’re giving this section probably more real estate than it deserves, because listening to the noise floor is a vague and inexact method of diagnosing an amplifier’s problems. The first piece of evidence that you have is the sound that the amplifier actually is making: the noise floor. You can use your knowledge of how an amplifier works, along with the evidence that your malfunctioning amp is giving you. In most cases, you don’t even need test equipment to determine where the problem is hiding. The good news is that most problems can be narrowed down to small portions of the amplifier. The bad news: a “no signal” problem can dwell anywhere in the amp circuit. So, do not use a valuable speaker for this test. Shorted output transistors or a faulty output transformer can destroy a speaker in an instant. You can always do the reverse - test a known working speaker in the questionable amplifier - but there is a chance that the amplifier is malfunctioning in a way that damaged the speaker in the first place. One way to do this is to test the speaker in a working amplifier. For this reason, you should always be suspicious of your speaker until you can prove that it is functioning correctly. Is the speaker blown? Many symptoms of a blown speaker imitate symptoms of a malfunctioning amplifier. If it is facing away from you, turn it around. Just be aware of the position of the speaker. This isn’t to suggest that you should smash your face against the speaker cloth for a closer listening experience: if there is an unexpected loud noise, you may damage your hearing. You may need to get physically closer to the speaker than you would otherwise position it during normal use. When testing, make sure that the speaker is pointed in your general direction. Turn the instrument up and make a thorough test before making your conclusions. In this case, hum will also be attenuated, so you can’t necessarily make a determination of “no sound” by the absence of the usual noise floor. In some cases, the signal is extremely attenuated but very, very faintly audible. Give yourself every possible advantage when troubleshooting and always listen carefully before concluding that the speaker has no sound. Any audible signal, audio or otherwise, is a good clue. Listen to the speaker carefully, in a quiet room, to confirm that it is, indeed, not passing any signal whatsoever.

These possibilities are discussed in the guide, My amp doesn’t turn on. There might also be an interruption in the early power supply: for instance, a failing power transformer. The speaker wiring has deteriorated, or the jacks have rusted to the extent that they can no longer make the proper connection The output transformer is open or otherwise faulty However, it is certainly possible for the speaker to be interrupted in a way that also silences the speaker.

This is because, in many cases, the signal is interrupted well before the speaker, leaving the speaker to transmit any incidental noises that enter the circuit outside of the fault area. For instance, you may hear hum, hiss, reverb crash (if applicable), or even popping sounds when connecting or disconnecting inputs. Usually, in a no-sound scenario, you will hear some sound coming from the speakers, even if the signal path happens to be cut off. If you don’t see these things, you should read the guide My amp doesn’t turn on first. If you see tube glow and the pilot light is on, that is an indicator that the early power supply is functioning correctly (i.e., your amp turns on). If there is absolutely nothing coming from the speakers, you should distinguish between an amplifier that is not turning on and an amplifier that is not passing signal.

Hifonics amp wont turn on