[jdandy]

bodiezaffa.......Your volume knob is not a zero to 100% output level control, and 12 o'clock is rarely 50% of output. In fact it is usually well past 50% output, especially the peaks. Your maximum clean volume is not necessarily based on the volume position as much as it is based on the dynamic range of your source material.

You must remember that every 3 decibel increase in output (volume level) requires a doubling of output power. If you are listening to music with an average volume level of 15 watts, your peaks are likely 10 to 12 decibels higher. Doing the math, that equates to 150 to 240 watts of output power required to faithfully reproduce the music without clipping the peaks. Lets assume this is happening at the the 11 o'clock position on your volume knob with a given piece of music. You are essentially using every single watt your integrated amplifier is capable of delivering within its distortion rating. Turning the volume knob to 12 o'clock will push the amplifier into clipping on the peaks because you are now trying to get 300+ watts on peaks from an amplifier only capable of delivering 200 watts.

Another thing to keep in mind is the amplifier's power supply and its ability to deliver a continuous voltage supply to the output stages at maximum rated output. Many amplifier designs can achieve maximum rated output, yet the power supplies are not sufficiently stout enough to maintain the amplifier's maximum output for any length of time. This is often the case with many integrated amplifier designs, as space and weight considerations during the design take precedence over what might otherwise be necessary for a premium grade power supply section. I am not saying this is the case with your Luxman 507u, but it could be part of the equation that is adding to your integrated amp's dilemma. You may be expecting more performance than the Luxman integrated is capable of delivering, even into the 91 dB efficient Sonus faber Cremona M's.