Before Sonos became known as a speaker company with devices such as the One and the Beam, it produced a line of add-ins for existing systems and speakers. The $500 Connect:Amp debuted in 2009, and almost a decade later it's finally getting an refresh.

The new $600 Sonos Amp sports a number of upgrades that should appeal to both the custom integrator and the home user. This compact two-channel amplifier can power whatever speakers you hook it up to, integrating them with Sonos' whole-home system. 

Like other Sonos gear, it can be controlled by your phone to play audio from pretty much any music source you want, including Spotify, Pandora and Apple's iTunes, either by itself or as part of a multiroom Sonos system. Although it lacks an onboard microphone, it will also be controllable via Alexa voice commands if you own an Alexa-capable device like a Sonos One ($199 at Amazon.com) or Beam, or an Amazon Echo ($100 at Amazon.com) speaker. When Sonos launches support for Google Assistant, the Amp will work with those devices too.

Other features include:

• 125 watts per channel -- twice the power of the original model.
  
• A new HDMI input, or optical input with the optional adapter
  
• AirPlay 2 support for Apple devices
• Stereo RCA line in
  
• Subwoofer output
• Can be used as part of a 4.1-channel surround setup, with two Sonos Amps and a phantom center
  

One of the main problems with the original Connect:Amp was that it didn't really synchronize with audio from a TV. The new HDMI input promises easy AV sync when connected to a television, and audio from the TV can pass to the amp via Audio Return Channel (ARC) -- similar to the Sonos Beam ($399 at Amazon.com). That also means you can listen to TV audio elsewhere in the house on another Sonos speaker.

Design-wise, the Amp is essentially a shortened, black cube at 8.54 inches square and 2.52 inches high. It includes internal heat sinks so it can be stacked with other amps, though the company suggests active cooling in professional applications.

The front of the unit is minimalist, with a play/pause button and an area you can swipe for skipping tracks as well as volume up/down. The back of the Amp has a pair of proprietary thumb-screw speaker terminals but these can be removed completely to reveal normal banana plug inputs. There's also an Ethernet port in case you don't want to rely on Wi-Fi.

The Amp doesn't include the digital-to-analog converter found on most of its kind, instead using a Qualcomm DDFA amplifier, which keeps the signal digital until the last possible moment. The analog input still features an analog-to-digital converter though, and the signal -- say of a record player -- can be streamed to other Sonos units in the home.

I've seen plenty of compact amps based on Class D technology, but some -- such as the Creative X-Fi X7 -- are less than "serious" audio components. With its power upgrade, hopefully the Sonos Amp can finally compete or even better the likes of the Marantz NR series or the Elac Element.

The Amp can also be run in conjunction with a wireless Sonos Sub or with a pair of smaller Sonos speakers, such as the Play:1s, as rears.

I heard the Sonos Amp connected to a pair of Bowers & Wilkins 702 S2 speakers at an event in Boston last week, in the same room as I first heard the Sonos Playbase ($699 at Amazon.com). While the demo wasn't as attention-grabbing as the Playbase, the Amp nonetheless demonstrated how it could operate as a straight two-channel amp or be split to operate as part of a 4.1 setup. I look forward to testing the amp in the CNET office, but maybe a pair of the more affordable Bowers & Wilkins 606 would make a better fit.

With all of the improvements, at $600 the Amp is $100 more expensive than the previous version. It will be available from December on the Sonos website and to custom installers in the US, and will go into worldwide distribution in February 2019. It'll cost £600 in the UK and AU$1,000 in Australia.

While we're on the topic of upgrading aging components, one thing I'm still holding out for is an update on the company's oldest product, the ZP100 (now Connect). A $350 Wi-Fi dongle was a big deal when it was released, but even the new Works With Sonos program -- a Sonos Connect operating in tandem with an Onkyo receiver -- can't help the device compete in a world where the $35 Chromecast Audio ($35 at Dell Home) exists. Here's hoping.

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