Expert Pro systems come with a 2-year warranty. Effective from date of purchase.
The ideal situation is to have no limitation in terms of thermal dissipation and current availability. This is the case with the 250 Pro where the output power in dual-mono is then 4 times higher than the output power in stereo (the output power P goes from 250W to 1000W as the output voltage U is multiplied by 2 in dual-mono and P=U2/R). With the 220 Pro, the casing is limiting the thermal dissipation in dual-mono mode and therefore the output power is only multiplied by 2. With the 140 Pro, the class D board is limiting the current availability and therefore the output power is only multiplied by 1.5.