Network Bridge II inbuilt. (DOP 06/2018)
Preloved PS Audio PerfectWave DirectStream Junior, Silver. 1 owner, excellent condition, original packaging, 30 day warranty
DSJ is a technological wonder that builds on the same architecture awarded Product of the Year in both Stereophile and TAS, Darko Knock-Out award, Editors' Choice and Golden Ear awards. DSJ is an extraordinary performance instrument–handwritten and uncompromised – a pure DSD Digital to Analog Converter uncovering all the missing information long hidden in your audio library, from both PCM and DSD sources.
CD's, high-resolution PCM, or DSD based media, are expertly upsampled to twenty times DSD rate and output as pure analog directly into your amplifier or preamplifier. DSJ is one of the few, true, fully analog DSD devices, that's setting the industry on its ear and reshaping the landscape of music and high-end audio.
The PS Audio PerfectWave™ DirectStream Junior Digital to Analog Converter (DAC) is a state ofthe-art DAC, preamplifier and media centre. DirectStream accepts PCM as well as DSD Digital Audio data and converts it to high-performance analog audio that can be fed directly to a power amplifier or preamplifier.
DirectStream Junior, based on its larger sibling, the DirectStream DAC, represents a major advancement in the art of recreating the musical event.
Musical information that may have previously been hidden (or covered up by other DACs) in digital audio media ranging from CDs to high resolution downloads will be uncovered by DirectStream Junior.
Subtle musical details and cues such as upper harmonics, decay, reverb and room reflections will no longer be masked by the conversion process from digital to analog. Your music will sound natural, and you will be able to rediscover much of what you may have been missing in your digital audio library with the introduction of DirectStream Junior into your system.
DirectStream Junior features a unique architecture inside. From its digital inputs to its simple output stage, DirectStream Junior has been hand written, hand designed and personally voiced by its designer, Ted Smith, along with PS Audio CEO, Paul McGowan and legendary loudspeaker designer and founder of Infinity Loudspeaker Systems, Arnie Nudell.
DirectStream Junior is based on a FPGA (Field Programmable Gate Array) as its core processor and no off-the-shelf DAC chips are used in its design.
DirectStream Junior is less sensitive to the vagaries of input source types and their level of jitter than most DACs made. Remarkably low jitter sensitivity is one of the hallmarks of this design and is accomplished by not using classic edge transition detection techniques on the digital input data.
Instead, a proprietary method of extremely fast sample-and-recognize technology is employed that reduces dependency on cables, jitter and the quality of the incoming data source.
Once the data from the selected digital audio source has been input to DirectStream Junior, it is upsampled to ten times the standard DSD rate of 2.8MHz before any processing takes place. After processing by DirectStream Junior, all input data is converted to double rate DSD (5.6MHz) and output through a passively filtered solid state analog section.
DirectStream Junior is entirely DSD based, even for PCM inputs. DSD was chosen as the core engine for this instrument for a number of compelling reasons:
- DSD is simple to convert to analog: just low pass filter it.
- DSD is inherently linear: it’s hard to build a PCM DAC that always takes the same sized step in the output for any possible unit increment of the representative PCM voltage value. The best PCM technology for linearity is arguably a resistor ladder, then all steps are at least positive for a positive change in the input, but making resistors that are accurate to one part in 2^16 is hard and to one part in 2^20, very hard. DSD doesn’t need anywhere near this level of component matching to achieve its excellent results.
- DSD soft clips when overdriven, more like magnetic tape: signals which exceed the nominal full scale value only get slightly compressed, if at all. With PCM, you either have flat tops which induce extra energy at the squared off edges or, worse, you can have wrap around, which is very audible.
- All bits in a DSD stream have the same weight: a single bit error anywhere is barely measurable, let alone audible. Some bits in PCM carry a lot of weight and would make a very loud pop if changed. PCM needs more error recovery to keep to a given signal to noise ratio (S/N) with a slightly corrupted digital signal.
- Ironically, most sanely priced PCM players actually use DAC chips that utilise a sigma-delta modulator (DSD) to get a DSD-like signal anyway. Similarly, many (most) A/Ds are sigma-delta based. The typical PCM path is analog -> DSD -> PCM -> disc -> PCM -> DSD -> analog. The DSD path can skip the conversions to PCM. Those conversions can’t be perfect, and artefacts of the steep anti-aliasing filter or the reconstruction filter aren’t considered benign by many.
- DirectStream Junior handles the PCM conversion from AES/EBU, S/PDIF, TOSLINK, I2S and USB without recovering a clock by simply watching for the edges and making decisions about what they mean in context. The result is that any jitter present on the input is lost entirely in the FPGA. There is little difference between TOSLINK or I2S because the output clock’s rate only depends on the long term average rate of the inputs not on any edge or other local feature.
The heart of DirectStream Junior is the DSD engine itself. Regardless of input format, whether PCM or DSD, all data are upsampled to 30 bits running at 10 times the standard DSD rate and then back down again to double rate DSD for noise shaping.
The internal volume control keeps complete precision: every bit in the input affects the output of the DAC for any volume level. Except for the sigma-delta modulation process itself, there is no rounding, dither, or other trimming - not to 24 bits, not to 32 bits, not to 48 bits, but rather a full 50. The incoming PCM signal is 30 bits from the upsampling filter, and the volume control is 20 bits wide, so all 50 bits
of the output are used throughout the sigma-delta conversion, requiring more than 50 bits of precision.
DSD only requires a nominal 20 bit signal to noise ratio. This design utilises a minimum width of 24 bits with wide filter coefficients and 144dB S/N. Use of full precision everywhere and many guard bits in the IIR filters and the sigma-delta modulator help maintain our goal of perfecting the audio output.
While some designs may run out of headroom or approach saturation levels, depending on the source material, the new design opts for an extra top bit everywhere in the digital path coupled with an extra 6dB of head room in the analog path beyond the 6dB of headroom that SACD uses. The top bit keeps PCM from saturating, even if that PCM was not properly bandwidth limited in the initial recording process.
The output of the DSD engine is fed directly into the output stage, based on high speed video amplifiers and a passively filtered solid state output stage.
Most output schemes for DSD modulators are active low pass filters, covering the required 120dB S/N ratio from 10Hz to 220MHz and have a number of design challenges and problems associated with even the best designs.
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