Reconstruction Filters - Wells JASON Owner's Manual

OWNERS MANUAL FOR WEISS JASON CD TRANSPORT

Reconstruction Filters

Reconstruction filters have been mentioned in the "Upsampling, Oversampling and Sampling Rate
Conversion in General" paragraph above. If you have read that paragraph you know what the
purpose of the reconstruction filter is. The main point about this analog filter is that its frequency
response should be as smooth and flat as possible in order to have a virtually linear phase
rd rd
response. The MEDEA employs a 3 order filter for that purpose. 3 order is sufficient to suppress
the frequencies above approximately 176.4kHz. 176.4kHz because the D/A converter in the
MEDEA is running at 352.8kHz (or 384kHz) sampling frequency.
Analog Output Stages
The MEDEA employs class A output stages with a virtually zero ohm output impedance. Class A
inherently guarantees very low distortion figures even when operating the amplifier in open loop,
i.e. without feedback. The feedback is added to lower the distortion figures even further. The
distortion figures of the MEDEA, which by the way are excellent, are predominantely caused by the
D/A converter and not by the output stage.
A very low output impedance assures that the performance of the MEDEA and the subsequent
amplifier combination is not compromised by the cables between the two or by the input
impedance characteristics of the amplifier. A low output impedance can be difficult when it comes
to stability issues, but we have taken care of that problem in the MEDEA.
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Page: Date: 10/04 /dw