John
CPLD. “Can punch low down”? For Colorado’s PS Audio the past twelve months’ show promo has centred on the soon-to-be-released BHK Signature 250 power amplifier: 250wpc into 8 Ohms, 500wpc into 4 Ohms, 6922 tube input, MOSFET output, US$7499. BHK? Them be the initials of the amplifier chief designer Bascom H. King.
A prototype handled the BHK Signature’s public debut at RMAF last October…
…before a finished version was hauled to CES in January 2015 (detailed here) to serve as a static display talking point…
…which in turn led to a real-life outing with Magnepan 20.7 loudspeakers at May’s Munich High End Show…
…and then two weeks later a pair of 300wpc monoblocked BHKs (US$15000/pr) lit up Irvine at T.H.E Newport Show:
…
..which aren’t pictured above (ha!) because a) three shots of the same amplifier is an elegant sufficency and b) you need to marvel at the view enjoyed by Paul McGowan and co. during the 3.5 days demo-ing said amplifiers at the Hotel Irvine.
Four separate sightings by yours truly at four separate shows. That’s some serious touting by the Boulder manufacturer. You’d therefore reasonably expect the PS Audio press release that hit the DAR inbox yesterday morning to be more of the same: a trumpeting of the BHK Signature 250’s (and 300) formal release date.
But no.
Instead, an announcement of the revised NuWave DAC which itself supplanted the Digital Link III at the tail end of 2012. On the surface it looks simple enough: the NuWave DSD updates the forerunning NuWave with DSD playback capabilities whilst adding an I2S input to its forerunner’s asynchronous USB, coaxial and toslink digital inputs – all of which are sample-rate conversion free.
The NuWave DSD will read up to 32bit/192kHz PCM on all but the toslink input (which is capped at 96kHz). Single- and double-rate DSD feeds must be piped in via I2S or USB.
It’s on the inside that things have been switched up more significantly.
“What makes the NuWave DSD so great? We’ve taken the lessons learned from DirectStream, and applied them to a smaller-scale, lower-cost unit,” reads the press release.
That doesn’t mean you’ll get Ted Smith’s FPGA decoder for US$1295. Decoding is still handled by a traditional off-the-shelf DAC chip. For this DSD iteration, that means an Sabre model from ESS Labs, switched up from the predecessor’s TI/Burr Brown silicon.
“Which ESS chip, Mr McGowan?” hollered I. Despite the choice of decoder silicon being only one of several influencers of a DAC’s sound, consumers like to know.
McGowan spills the beans: “It is the ES9010K2M which is out of their portable series of reference DAC chips. We chose it from testing a bunch of different ones and found this to be the most musical. Because it was developed as a portable DAC we had some power supply challenges but those were solved by Bob Stadtherr in engineering. The choice of a passive filter after the DAC and before the output stage was critical.”
Handling input data is something called a CPLD (Complex Programmable Logic Device) – reportedly a “simplified FPGA”. The CPLD analyses the incoming signal’s format and sample rate, re-clocks it and thus (hopefully) reduces jitter before “waveshaping” the data and sending it on to the ESS Sabre DAC chip.
An email back and forth with Mr McGowan takes us further into the technicalities: “The CPLD is a smaller FPGA, just not as many gates, but allows us to perform complex processing on the data. One of its primary functions is to organize all data the same, so if the XMOS feeds the CPLD or the input switch from S/PDIF or I2S, data is first organized in something similar to a RAM buffer, wave shaped and then output with our own clock to the I2S inputs of the Sabre [DAC chip]. Had we used a standard switch to simply select which input fed the DAC, each would have had a different sound, some better some worse. Using the CPLD to organize, identify and shape the data regardless of input, not only helps with consistency of performance but everything played through the system is improved regardless of quality of source.”
Perhaps the single biggest influencer of a DAC’s sound is its power supply. As well as “7 regulators, properly-bypassed high-speed switching diodes, and a massive 15,000 mFd of storage capacitance”, the NuWave DSD DAC’s mains juicer comes in the form of a larger-than-usual toroidal, similar to that found in the NuWave Phono Converter and consistent with other PS Audio products, including the aforementioned BHK amplifier.
Lastly: “The output stage is a unique Class-A configuration, fully balanced and direct coupled hybrid array (utilizing both discrete semiconductors and ICs), with an extended bandwidth of -3dB at 60 kHz!”
The NuWave DSD DAC comes in black or white and will sell for US$1299 – that’s US$300 more than the outgoing version.
Further information: PS Audio
