Most likely a ground loop. Do you have a loop breaker set up?
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
at the moment, its on the bench, only psu is grounded. input is from a phone on battery power.
edit: ha.. ive just realised the earth/ground pf the psu was not connected.. so absolutely zero grounding.
wonder if that might have been the cause. im away from my shed at the moment so i cannot test until later.
edit: ha.. ive just realised the earth/ground pf the psu was not connected.. so absolutely zero grounding.
wonder if that might have been the cause. im away from my shed at the moment so i cannot test until later.
Looking at the TPA3255EVM schematic, there's a 100k ohm resistor to ground at the inputs. Would that not result in a 100k ohm input impedance?
The manual doesn't specify the input impedance.
Thanks, Mike
Hooked 'er up to a Peaktech 6225A lab supply, giving the maximum 31V and it sounds great. Quality seems in the same league as my ice power 50asx2 but more powerful. Its only drawing 0.1 - 0.15A on normal listening level, which is already too loud for having a conversation. I've seen up to 0.4A but that was party-like uncomfortable loud just for testing. Max draw on startup seems to be 0.8A but I'm not sure what the supply would show if the peak is very short. My speakers are Klipsch rp-160m with 96dB (which is said to be too optimistic). I'm not arguing for a power supply this weak, and heavy bass can quickly draw more, but I will surely have no reason to upgrade from one of the recommended Mean Wells with 7 - 10A which I otherwise had considered ;-)
Well it seems extremely tolerant, I could go down to 16V and not hear any difference. Now running with a HP switch power supply brick style, 48V 1.75A (so less power than 90W suggested above), that sounds great too. I don't seem to hear any differences with this board.
Is anyone experiencing differences in sound with different supplys?
Is anyone experiencing differences in sound with different supplys?
The supply voltage can make a big difference at some ICs (IRS2092 i.e.), not so much at others (STA516 i.e.). My biggest concerns (besides noise) would be reliability, a lot of these bricks melt or burn with overload.
No, input impedance is determined by the 10k resistor to NE5532 negative input in parallel to 100K resistor, so about 9k input impedance.
In layman terms, the positive input of NE5532 is fixed to half Vdd (pin 3) and it at all times "tries" to adjust the negative input to the same voltage, thus acting as a virtual ground. It does that by adjusting the output rail (pin 1) to compensate for the input signal coming in on pin 2, carrying the inverted input signal to the next stage.
In layman terms, the positive input of NE5532 is fixed to half Vdd (pin 3) and it at all times "tries" to adjust the negative input to the same voltage, thus acting as a virtual ground. It does that by adjusting the output rail (pin 1) to compensate for the input signal coming in on pin 2, carrying the inverted input signal to the next stage.
Okay, to shorten that.. the IRS2092 amps usually benefit from higher supply voltages.