Use new imported TDA7379 amplifier chip, with fever AD828 preamp.R8, R10 is the magnification setting resistor (default delivery is about 2-3 times magnification, according to their need to change the magnification from 10k-47k resistor between select, the greater the resistance.the higher the zoom factor, if it is used plug-in resistors, chip resistors can take down the original, the plug-in resistance welding position on the patch ends of the pad).Preamp input and output coupling capacitors Promise of imports fever capacitance, better than the polarity effect.Maximum output power: 39W X 39WOperating voltage: DC 9-17.5VBoard dimensions: length xwidth(50mmx33mm)/1.97x1.30 inchmaterial:plastic,metalcolour:redPackage Included:2x TDA7379 Amplifier + AD828 Preamp BoardOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.