Timeline for Why a 1 A pedal power supply can't power a 750 mA practice amplifier?
Current License: CC BY-SA 4.0
10 events
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Feb 11, 2021 at 20:05 | comment | added | fraxinus | There may as well be ground loop inside the amp (bad engineering, that is). The amp can as well hum by some mechanism other than the ground loop. But it is better to spawn another question at EE.SE | |
Feb 11, 2021 at 19:54 | comment | added | Tim | @fraxinus - yes, just sharp of G. Been there done that, many times, but I'm trying to establish how it happens when there's only the amp. that's earthed. For a loop, there needs to be other components, or am I going bonkers? | |
Feb 11, 2021 at 19:06 | comment | added | fraxinus | @tim pretty much the usual way to pick up a grid hum is via ground loop somewhere. In UK, it should be between G ang G# (50Hz). | |
Feb 11, 2021 at 18:29 | comment | added | user1079505 | @Tim the nomenclature is a bit confusing here. Word ground is used to describe safety connection to earth, but it also means a reference potential for an electrical circuit. If you make a large, closed loop out the ground line, it may pickup electromagnetic noise from nearby devices, regardless of whether it is connected to earth or not. The most common source of noise is the 50 or 60 Hz oscillation from the mains, but it could be something else, e.g. from switching power supplies, frequency converters... | |
Feb 11, 2021 at 17:12 | comment | added | Tim | @user1079505 - I understand - it used to happen at one particular venue I played frequently - in UK almost a G pitch ( I guess 60 Hz), but would that actually be a ground loop - earth hum, per se? | |
Feb 11, 2021 at 16:59 | comment | added | user1079505 | @Tim As fraxinus explains, mass of various devices is connected via the signal cable shield and via the power supply. This forms a loop that might pickup noise. | |
Feb 11, 2021 at 15:09 | comment | added | Tim | In the past, I've got rid of earth loops by (naughtily) removing an earth connection. If that's not there in the first place, as in most power supplies, how can the lack f it produce hum? | |
Feb 11, 2021 at 14:59 | comment | added | fraxinus | The loop is between the power supply, the first device and the second device. | |
Feb 11, 2021 at 14:16 | comment | added | Tim | How would ground loops come from wall warts that had no earth pin connected? Most are live and negative, the earth pin not being connected. | |
Feb 11, 2021 at 12:52 | history | answered | fraxinus | CC BY-SA 4.0 |