Digital Processor Reviews

In his report, in the November 2016 issue, on the Torreys firmware upgrade for PS Audio's DirectStream D/A processor ($5999), Robert Deutsch wrote that he had noticed "an increase in resolution"—and at that, my ears pricked up. I had purchased our original review sample of this processor following Art Dudley's favorable review in September 2014, and I had upgraded it, in the summer of 2015, to the Yale operating system, which I prefer to the earlier Pikes Peak and v.1.2.1 versions. As much as I enjoy the sound of the DirectStream, I had always been bothered by the fact that its ultimate resolution was limited by its analog noise floor.

According to PS Audio, not only does the Torreys upgrade enable DirectStream DACs with the optional Bridge II network card to act as an endpoint for the Roon music management system, Torreys "further reduces DirectStream's sensitivity to jitter, and adds proprietary resource-management within the [Field-Programmable Gate Array]. Other advancements include better low level linearity at low volume levels; improved gapless DSD support; improved sigma-delta modulators; and improved high-frequency noise performance."

I am not a Roon user but these other benefits sounded tempting, and I installed Torreys on my DAC. The necessary files are packed into a Zip container that can be downloaded from PS Audio's website. After the files are unpacked, they are copied onto an SD card which is inserted into the appropriate slot on the DAC's rear panel, with the power off. When the power is then turned on, the DirectStream loads the new firmware from the SD card. After the installation, you can check that it has been correctly installed by pressing the gearwheel icon at the top left of the front-panel display.

Before I did any listening, I performed a full set of measurements with my recalibrated Audio Precision SYS2722, but to my surprise, I didn't find any differences. Fig.1 shows the spectrum of the DirectStream's output with the volume control set to its maximum with a dithered 24-bit 1kHz tone at –90dBFS with the Yale OS (blue and red traces) and Torreys OS (green, gray). The two sets of traces overlay exactly.

Similarly, the spectrum with a full-scale, 24-bit 1kHz tone with Torreys (fig.2, green and gray traces) was identical to what I had found with Yale (blue, red), even down to the very low-level 100Hz-spaced sidebands around each harmonic.

But when I listened to the PS Audio with the Torreys firmware, while the DirectStream DAC didn't have the low-frequency authority that makes the dCS Rossini Player I reviewed last December stand out from the crowd, I had to agree with Bob Deutsch. Even without greater measured resolution, it did indeed sound as if there was more resolution. I switched back between Torreys and Yale and back to Torreys and the impression of greater resolution with Torreys persisted. A paradox.

I wrote in a follow-up in the March 2015 issue, where I had found that the v.1.2.1 firmware had given measurable improvements in performance over the original v.1.1.4 firmware, "The new firmware is a gift to end users that will keep on giving." Torreys is another such gift.—John Atkinson