Written on: 12/08/2013 by Drastic (14 reviews written)
The “Little Bear P3 Pre-Amp” is a pre-built 3 valve unit available from our friends in China (see e-bay). The amp is supplied complete with valves & transformer plus a clear perspex top & bottom cover. You are required to fix the covers in place and connect up the wires from the transformer to the screw connectors on the amp board (all marked), all in all 10 minutes work, now fit the values then she’s ready to run.
The valves are two 6N3 (double triodes) plus one 6Z4 (rectifier), cheap to replace and easy to get on e-bay.
Sound Test :- First thing to come to light is theres FAR TOO MUCH GAIN, with the pre-amp plugging into a Power amp you could hear the sound with the volume control OFF. Turn the volume control up just a tad & your pumping enough sound for a disco.
The two output resistors (260K) next to the volume pot should be changed for 3.9Meg ohm, this reduces the gain to a usable level. There maybe a better way to reduce the gain,but without a schematic it’s hard to see what’s what as it’s a double sided PCB.
The sound quality it very good indeed! there was no hum what so ever, the bass was well controlled but at first lacked a little firmness, with a detailed mid range, the treble seemed a little sharp, but the valves have still to run in. After only a couple of hours the bass sounded more solid & the treble sharpness was less
noticeable, also she was on the stock Shuguang valves, which did sound fine, but better are available.
It’s a very good piece of kit, very good quality sound, you wont buy better for less than £50 !
The only thing against it is the top & bottom covers, they could allow a stray finger to touch a high voltage connection, but the average DIY person could easily add extra protection to prevent access.