Gmood1...
1...While the power capability (watts) of the amp has no direct relationship to its noise level, it does affect how the noise level is spec'd. Noise is spec'd relative to full power output. So a 60 watt amp rated at -100dB will be quieter at idle than a 600 watt amp with the same noise spec.
2...An AC powered dc supply can be as quiet as the designer cares to make it. And battery voltage has some noise on it when you draw current. The chemicals are "cooking off" to release the electrons. However, in practice battery power is a foolproof approach if the device doesn't require much power.
The noise generated by an ac supply is easily evaluated. Just pull the plug so the amp is running on the capacitors and see if the noise level changes. Make sure that you aren't hearing ground loop hum.
1...While the power capability (watts) of the amp has no direct relationship to its noise level, it does affect how the noise level is spec'd. Noise is spec'd relative to full power output. So a 60 watt amp rated at -100dB will be quieter at idle than a 600 watt amp with the same noise spec.
2...An AC powered dc supply can be as quiet as the designer cares to make it. And battery voltage has some noise on it when you draw current. The chemicals are "cooking off" to release the electrons. However, in practice battery power is a foolproof approach if the device doesn't require much power.
The noise generated by an ac supply is easily evaluated. Just pull the plug so the amp is running on the capacitors and see if the noise level changes. Make sure that you aren't hearing ground loop hum.