This is the PCB of a very low distortion preamplifier that can accept balanced signal source. Within the board the balanced signal is converted to unbalanced output. The circuit make uses of a famous balanced line receiver SSM2141. The chip can offer a distortion as low as 0.002% across the whole audio frequency band. This is followed by another opamp stage.The gain is also adjustable so as to complete a preamplifier function. Besides being a balanced to unbalanced conversion amplifier, this board can also be used as a summing amplifier. One of the application is a low distortion two-input audio mixer. Another application is to sum the left and right channel signal to form a mono signal. Many audiophiles prefer the sound of mono to stereo for the perceptional purity of mono signal. This board would perfectly fit such summing function. When second stage (the opamp) can be inserted with opamp of one's preference. When a good driving capability opmp is used, the amplifier can even be used as a balanced input headphone amplifier !! Supply voltage : +/-9v to +/-15V. The PCB has a board thickness of 1.6mm, and copper thickness of 70um. This is four times normal board copper thickness ! The surface is gold plated and coated with two-sided solder resist for maximum durability. PCB dimension : 86mm x 50mm We provide schematic and part list to buyers by EMAIL( to be attached to the shipment notice). We do air shipping worldwide at US$4.00. We welcome combine shipping. Powered by SoldEazy