I bought a Slim Devices Squeezebox connected to Wi-Fi in early 2006 to experiment with streaming media. When Slim Devices released the high-performance Transporter, I purchased the review sample after measuring Wes Phillips in the February 2007 review, which left a deep impression on me. I have used Transporter for a few years, but at the end of 2006, after Logitech, which purchased Slim Devices, stopped supporting Squeezebox devices, I put it aside. By then, I had started to use Pure Music and Audirvana streaming media applications, I prefer Slim Devices' SlimServer software (footnote 1). But every few months, I will start Transporter, provide it with audio data through my network, and then spend a nostalgic night and enjoy everything it does.

Given this history, it is not surprising that I eagerly agreed to review HiFi Rose's RS250 Roon Ready streaming digital-to-analog preamplifier.

The RS250 is priced at US$2,495. This is a relatively small device. Its front panel is a large four-color touchscreen display that is almost 9 inches wide. On the right side of the screen are the standby button, volume control knob and 3.5 mm headphone jack. In contrast, the rear panel is very crowded, with a pair of single-ended analog inputs and several digital inputs: coaxial and TosLink S/PDIF; for USB Type B It is used to connect to the USB output of a PC or similar device; USB 3.0 Type A is used to connect to a storage device; and an Ethernet network port. RS250 has a pair of single-ended analog outputs and three digital audio outputs: coaxial and optical S/PDIF and USB Type A. Video output, resolution up to 3840 × 2160 at 60Hz, can be used on HDMI 2.0 port. The AC power supply is connected to the 15A IEC jack. In addition to these wired connections, RS250 also provides Airplay, DLNA, Roon, Spotify Connect, Tidal, Qobuz and other streaming services.

Internally, two ARM Cortex 64-bit processors-a dual-core Cortex-A72 and a quad-core Cortex-A53 with 4GB RAM-run the Android 7.1 operating system. The power supply is linear rather than switching mode, and has a configuration that is said to minimize electrical noise. The analog output stage uses the relatively new ESS ES9038Q2M two-channel DAC chip, which has a so-called "femto clock." Internal SSD data storage is an optional additional feature; this is not suitable for review samples.

This screen makes the RS250 both eye-catching and practical. When you turn on the device for the first time, it will prompt you to enter the time zone, country, and preferred language. After that, the horizontal flow of icons will be displayed. Too many icons, you need to scroll left or right to see them. Some are self-explanatory-music, video, Qobuz, tide, clock, settings, input and output settings-while others are mysterious: Bugs, RoseFM, RosePodcast, RoseRadio, RoseStore, RoseTube, CD playback, and CD ripping. (The RS250 does not have a CD drive.)

Press the "Settings" icon to adjust the display brightness, clock display format, the appearance of the VU meter that appears when playing music, and the order of rearranging the icons. You can also check the operating system version and IP address, connect to a Wi-Fi network, and watch tutorial videos. The input and output settings icon allows you to select external input, digital or analog, set the input to internal, default to network input, and select digital or analog output. When you select the analog output, a gear icon will appear, allowing you to select one of seven FIR interpolation reconstruction filters (see the "Measurement" sidebar); select a variable output level or eight from 100mV to 2.2V One of the fixed output levels; resample the incoming digital data (selection range from 44.1kHz to 192kHz); reverse the polarity; and use a 32-bit audio source to apply correction to the bottom 8 bits.

Setup and use When I turned on the RS250 for the first time and connected it to my network via Ethernet, it assigned itself an IP address and then told me that it needed to update its operating system. Indeed, the front panel display recognizes the system as "3.8.13" and the audio firmware version as "XMOS 3115". Then I set the time, my language and my country.

Roon recognized the connected HiFi Rose as an endpoint; I also connected the RS250's USB Type B input port to the USB Type A slot on the back of Roon Nucleus. When I select the USB input with the input and output setting icon of RS250, Roon recognizes it as an ALSA device. For CD playback, I used a 1m AudioQuest OptiLink 5 cable to connect the optical output of the MBL N31 player to the TosLink input of the RS250. I learned that the RS250's animated front panel meter does not work under S/PDIF and USB connections, and the metadata of the file will not be displayed with the USB data because it is the same when it is connected to the network or played from an external storage device.

I mainly use the single-ended analog outputs of the RS250 to connect directly to the Parasound block, and then these outputs are first connected to the PSB Synchrony T600 speakers I reviewed in November, and then connected to the GoldenEar BRX. The playback volume can be adjusted by Roon's level control (network and USB) or front panel knob or Bluetooth connected remote control (analog and S/PDIF input and local media). However, in most cases, I use the RoseConnect Premium app (v3.04.27) in a comfortable listening chair. This application requires iOS 13.0 or higher, and my old iPad Mini is running iOS 12.5.4, so I installed RoseConnect Premium on an iPhone 11 running iOS 14.8. RS250 is recognized as "ROSE 5-D". I used the application to log in to my Qobuz and Tidal accounts, and the Tidal and Qobuz albums I added to my Roon library appeared in the Tidal and Qobuz album window, including the application and the front panel display of the RS250.

I learned that certain audio settings can only be used through the In-Out Setting icon on the front panel display and the aforementioned gear icon. Based on my experience (footnote 2) on the reconstruction filter settings of other D/A processors using the ESS Sabre DAC chip, I selected the "corrected minimum phase fast roll-off" filter (see the "Measurement" sidebar) and set RS250 plays files at the original sample rate instead of up-sampling them. I don't have any 32-bit audio files, so I turned off "Low 8-bit correction for 32-bit sound sources".

The menu item allows the RS250 to access the music library stored on the NAS network drive. However, since my NAS is currently offline, I inserted a 16GB USB flash drive with some reference recordings into the USB 3.0 "in" port on the rear panel of the RS250. RS250 recognizes the storage device and asks me if I want to scan the content and create a database. After completing this operation, the album will appear in the music window of the application and the front panel after the delay. There is also an MPEG video file on the USB flash drive, I can play it with RS250, and the video image appears on the front panel display. Selecting RoseTube using the app or display will display a series of music videos on YouTube. Similarly, selecting Radio and (in response to the prompt) selecting "USA" as my country/region will display a list of Internet radio stations.

Footnote 1: Now called Logitech Media Server, this open source application is still being updated regularly. It can be used with servers such as the Antipodes K50 reviewed by Jason Victor Serinus in the November 2021 issue.

Footnote 2: See, for example, the discussion of filters in my comment on Okto dac8 Stereo.

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