T+A MP 2500 R digital media player Sidebar

Digital Seasoning

In line with T+A tradition, the MP 2500 R offers four custom digital filters for LPCM media that act in concert with a 3rd-order analogue Bessel filter. 'FIR Long' and 'FIR Short' are traditional linear-phase types while 'Bezier/IIR' and 'Bezier' are minimum-phase filters based on Bezier polynomials. FIR Long is the default filter, offering equal pre/post ringing and a brickwall roll-off (–0.2dB/20kHz, +0.25dB/45kHz and –6.1dB/90kHz with 48kHz, 96kHz and 192kHz media respectively). Phase distortion is low and rejection of aliasing images superb, but the ringing is not ideal. 'FIR Short' trades less pre/post-ringing for poorer rejection of out-of-band images (just –7dB versus –102dB for FIR Long). The two Bezier filters offer the same (negligible) stopband suppression as 'FIR Short' but with almost no pre-ringing in the time domain. While these filters modify the audioband with CD/48kHz media, they are ideal for 96kHz sample rates. Here, 'Bezier/IIR' offers a slightly brightened upper treble (+0.3dB from 10kHz-20kHz) with a roll-off thereafter (–4dB/30kHz to –28dB/45kHz) while 'Bezier' offers a gentler all-round response (–0.2dB/20kHz and –4.7dB/45kHz). PM



Time and frequency responses of FIR Short and Long filters [top, red/black] versus Bezier and Bezier+IIR filters [bottom, red/black]
T+A elektroakustik GmbH & Co. KG
Supplied by: Kog Audio, UK
01353 721089