Bunch purity measurements are widely based on the technique of Time Correlated Single Photon Counting using an X-ray Avalanche Photo Diode (XAPD) as fast detector. XAPDs are advantageous because their dark count contribution can strongly be reduced by choosing an appropriate discriminator threshold in the counting system (see e.g. G.Rehm, DEELS 2014). There exist commercial systems based on 5x5 and 10x10mm^2 windowless APDs, using a pre-amplifier design which was developed some years ago at ESRF. However, the experience from PETRA III shows that bunch purity measurements with these large area detectors may be hampered by X-ray fluorescence caused by scattered background (see e.g. G.Kube, DEELS 2014). In order to reduce this background, in the future it is planned to use XAPDs with a smaller round active area with a diameter of 3mm. Hence and additionally driven by the interest from user’s side, the development of a dedicated fast but low cost XAPD pre-amplifier system was initiated. This presentation introduces the current status of the amplifier design.