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Non-oversampling Digital Audio Converter
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Jundac Three - March 2011
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Jundac Three push the TDA1543 to 192kHz...
The Jundac Three is a 16bit non-oversampling digital to analog converter.
It integrates one S/PDIF or AES/EBU input, an optional input clock and stereo fixed analog output.
The DAC chip is Philips TDA1543; it can operate from 32kHz to 192kHz sampling frequency.
The I/V stage uses discrete, solid state technology, in an open loop (feedback-free) configuration.
A non oversampling DAC don't use any digital filter. Data coming from CD are directly converted to analog;
there is no coloratura introduced by digital filtering, noise shaping or dithering.
Before output, the signal is smoothed by a sweet first order low pass filter. To reach best listening quality,
it can be coupled to an synchronous or asynchronous low jitter clock.
Power supplies in a DAC are critical to the overall design. The Jundac Three uses six very low noise
separate regulators. These power supplies use polypropylene capacitors and two separated power transformers.
To achieve the full music sonic attributes, we recommend using 200VA to 300VA power transformer
for analog section. This transformer powers the DAC stage and the analog section (I/V converter
and low pass filtering).
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Jundac Three - mounted
- click on the picture to show kit's details
- Assembled and tested
- Sold without transformers
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discontinued
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Recommended transformers
- 1x9V 20VA for digital section
- 2x24V 200VA for DAC and analog
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Technical documentation
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Technical description
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The Jundac Three use Cirrus CS8416, 32K to 192KHz DIR
(digital interface receiver) chip. The CS8416 provides digital de-emphasis needed for reading some CD
recorded with pre-emphasis.
Before DAC, digital data are re-clocked to avoid digital delay and reduce jitter and noise; re-clocking can be synchronous or asynchronous.
The DAC chip is TDA1543 from Philips allowing 16bit resolution.
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Schematic
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The data stream feed a TDA1543 16 bit DAC chip followed by feedback
free I/V stage with very sweet low pass filter. The low pass filter is first order filter cutting
at 170KHz using polypropylene film and foil capacitor. The BC550C were chosen for their high quality sounding,
each transistors are matched.
The Jundac Three uses very low noise regulators:
- LT1763 for the digital section (digital decoder),
- LT3080 for analog and DAC stage.
The analog section use three very low noise regulator LT3080 form Linear Technology in a semi-parallel configuration.
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In a semi-parallel regulator, i3 is adjusted to never become negative. Thus, the analog stage is never
directly powered by the regulator, this improve transient response. The LT3080 ensure line regulation.
Pictures of analog signal:
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Low filtered output signal
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Detail
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Dirac impulse response
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Power supplies
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Power supplies in a DAC are critical to the overall design. The Jundac Three uses six very low
noise regulators: three for the analog section and three for digital section. These power supplies
use polypropylene capacitors and two separate power transformers. For electrolytic capacitors, Elna Silmic II for analog,
and Nichicon LF for digital, are used. MURS320T3 state-of-the-art surface mount rectifier diodes from ON Semiconductor are
used in analog stage.
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Detail of 75 ohm load resistors on TDA1543
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Nichicon LF for digital ps
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Wima polypropylene film cap
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Diagram of power supply
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There is three LT1763 for digital section in a cascaded configuration (+8V, +5V, +3.3V) and three LT3080 for analog section
in a cascaded configuration (+27V, +22V, +7.5V).
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