CD player and USB-DAC
• Channel isolated double mono• Uncompressed Stereo Digital Signal
• TDA1540D converter in ceramic housing
• Synchronized oscillators of the TDA1540D
• Dynamic correction of the shift register
• Frequency compensation of the TDA1540D
• Class A operation of the TDA1540D
The result of this interaction is the audible achievement of a spatial and temporal precision. It is no longer necessary to ask the question of deep bass registers, of nuances or transparency of reproduction - the discussion about top performances in terms of sound is over here. Rather, new standards are set for continuity and naturalness of reproduction. Simply put, compared to the best digital playback devices, whether CD or streaming, a metronom sounds lively and authentic.
TDA1540 or TDA1541A?
Considering these converters individually, the TDA1540 has a 12 dB higher noise floor than the TDA1541A with 16 bits due to its 14 bits. With the SAA7000 connected upstream, the TDA1540 has a lower noise floor and therefore a higher dynamic range. The TDA1540 uses a separate converter chip for each stereo channel. The TDA1541A differs internally in that it has a second shift register to output both stereo channels, thus eliminating the need for a second analog converter. The incoming digital signal is divided between the stereo channels at the sampling frequency. For this reason, each shift register in the TDA1541A must be 40% smaller than in the TDA1540. The larger shift register in the TDA1540 results in more contoured details and a more balanced ratio over the entire frequency range. Thanks to its double-mono design with consistent channel separation and larger shift register, the TDA1540 is the better analog converter.14Bit, 16Bit, 32Bit?
It means the maximum size of the analog sine wave on the amplitude axis (up-down). A dynamic range of +6dB is assumed per bit. In audio engineering, dynamic range is specified in dB SNR and is the distance between the maximum possible amplitude and the existing background noise.Dynamic range = Signal Noise Ratio = SNR
The number of bits determines the distance between the background noise and the maximum amplitude and therefore the dynamic range. It does not mean the amount of information on the time axis (left-right). The amount of bits is sometimes mistakenly confused with the accuracy or amount of detail.
How much dynamic range is required?
Our voice has a dynamic range of 40dB. Acoustic music has a dynamic range of 80dB. A dynamic range reserve of 9dB is also required.A TDA1541 with 16 bits has a dynamic range of 96dB.
A TDA1540 with 14Bit has a dynamic range of 97dB!
Why does a TDA1540 have a greater dynamic range than 14x6=84dB?
A music CD is always read out with 16 bits. The TDA1540 is therefore preceded by an SAA7000, which interpolates the digital data and assigns it separately to the stereo channels. Together with digital noise shaping, this reduces the background noise by -18dB, resulting in a dynamic gain of +18dB.
Technical note Philips 1984
Dynamic range equals playback quality?
The dynamic range should exceed the value of 80dB required for music reproduction plus the headroom of 9dB. Analog converters from modern production exceed this value by up to over 100dB (32bit, 192dB SNR). The advantage is not due to better playback quality. An increased dynamic range is intended to help in the recording studio to move the real usable dynamic range further away from the background noise. It is assumed that less background noise is better. More modern findings show that reducing the noise floor much deeper than the inaudible range is more detrimental. A “sweet spot” is crucial, in which weak signals with stochastic resonance can take more energy. This also explains the preference of many listeners for vinyl records or tube amplifiers, which deliver poorer measured values in this range.Stochastic resonance, PDF document (german)
Simultaneous data format
No compression, no artifacts and no quantization errors. The simultaneous data format is an uncompromising data format for analog conversion - while traditional digital playback devices use the I2S data format, which compresses the stereo channels into just one signal. With the simultaneous data format, the stereo channels are processed separately and uncompressed in a separate converter chip per stereo channel. The converters do not have to re-allocate the bundled signal to the stereo channels. Stress-free, these can fulfill their actual task, plus: negative interactions, because both stereo channels are processed in the same chip, do not occur. From digital to analog output, a channel-separated dual mono setup is possible.Active correction metronome
The converter-internal shift register, which takes over the analogue conversion of the data from the bitstream, as it were, as a manual transmission, is controlled by internal oscillation. This is disadvantageous without metronome correction with a fixed frequency and not in dependence on the received data window. ThThrough the active metronom module on the converter, the oscillation of the shift register is adapted dynamically to the data window, a frequency compensation is performed and the converter output is set in class A.
The oscillator and shift register in the TDA1540 are controlled externally. A dynamic control depending on the data input, specifies the analog conversion in a new order of magnitude.