1. provides a volume control
2. provides switching to feed multiple sources to your amps
3. if so equiped, can provide balance and frequency controls
4. acts as a buffer so sources that need it can properly drive your amps
If you don't need any of the above, adding the active stages and cables associated with a preamp to a system can only degrade the sound.
If you do need the above, especially #4, then a preamp will make your system sound better.
Those who claim all systems need one have limited experience with systems that benefited from having one.
Some do, some don't.
2. provides switching to feed multiple sources to your amps
3. if so equiped, can provide balance and frequency controls
4. acts as a buffer so sources that need it can properly drive your amps
If you don't need any of the above, adding the active stages and cables associated with a preamp to a system can only degrade the sound.
If you do need the above, especially #4, then a preamp will make your system sound better.
Those who claim all systems need one have limited experience with systems that benefited from having one.
Some do, some don't.