SmartHomeScene Reviews the Apollo CAST-1: A Local Chromecast Audio Alternative for Music Assistant and Home Assistant
SmartHomeScene published a full review of CAST-1 on October 19. They set it up, streamed through Music Assistant, grouped it with other speakers over Sendspin, ran text-to-speech announcements in Home Assistant, and tested our optional Ethernet module. Their take is that CAST-1 "does an incredible job of streaming audio via Music Assistant."
Thank you to SmartHomeScene for the time they put into this. Here is what CAST-1 is, how it fits with the Open Home Foundation projects that make it work, and what the review found.
- What is CAST-1?
- A local Chromecast Audio alternative
- Music Assistant, Sendspin, and the Open Home Foundation
- What SmartHomeScene tested
- CAST-1 specs
- FAQ
What is CAST-1?
CAST-1 Audio Casting is a 45 x 45 mm network audio player. Plug it into powered speakers, a soundbar, or a receiver with a 3.5mm cable, power it over USB-C, and those speakers become a local, synchronized player for Music Assistant and Home Assistant.
Inside is an ESP32-S3 and a Texas Instruments PCM5122 32-bit DAC. It runs open source ESPHome firmware, so there is no account to create and nothing sent to the cloud.
A local Chromecast Audio alternative
Google launched Chromecast Audio in 2015 for $35. It was a small puck that plugged into the speakers you already owned and made them networked speakers. People loved it, and plenty are still plugged in today. Google stopped making it in January 2019, and nothing quite took its place.
CAST-1 fills that same spot behind your speakers, at $34.99. The difference is where it gets its music and who controls it.
- It is local. Audio streams across your home network from Music Assistant or Home Assistant. No cloud account sits in the middle.
- It is open. The firmware is ESPHome, and multi-room sync uses Sendspin, an open standard anyone can implement.
- It does more than music. CAST-1 is a full ESPHome media player in Home Assistant, so it also plays doorbell chimes, text-to-speech, and alerts.
- It is not a Google Cast receiver. You won't see it under the Cast button in a phone app. You play to it from Music Assistant, which can pull from Spotify, Apple Music, YouTube Music, TIDAL, Plex, and your own files.
If you have a drawer of old speakers or a receiver that never got smart, this is what CAST-1 is for.
Music Assistant, Sendspin, and the Open Home Foundation
CAST-1 is a small piece of hardware. The software that makes it useful comes from the open source community, most of it under the Open Home Foundation.
The Open Home Foundation
The Open Home Foundation is a Swiss non-profit that owns and protects Home Assistant, ESPHome, Music Assistant, Sendspin, and many other open source smart home projects, so no single company can buy them out or shut them down. It has two commercial partners: Nabu Casa and Apollo Automation. You can read how that partnership started in our commercial partner announcement.
Music Assistant
Music Assistant is a free music server that combines your streaming services and local files into one library, then plays them on speakers you already own. It supports Spotify, Apple Music, YouTube Music, TIDAL, Qobuz, Deezer, Plex, TuneIn, Audiobookshelf, and local files, and plays to Sonos, AirPlay, Google Cast, Home Assistant players, and Sendspin speakers like CAST-1. The queue lives on the server, so music keeps playing when you close the app.
CAST-1 shows up in Music Assistant automatically through mDNS. No pairing needed.
Sendspin
Sendspin is an open standard for synchronized whole-home audio, backed and governed by the Open Home Foundation. It keeps music in sync across speakers on your local network, with no cloud account. The spec is public and free to implement, and Music Assistant supports it natively. Sendspin is enabled by default on CAST-1.
Sendspin is still young. The spec is at the release candidate stage, so expect it to keep improving, and CAST-1 gets those improvements through ESPHome firmware updates.
What SmartHomeScene tested
Here is a summary of the review. Read the full CAST-1 review on SmartHomeScene for the details and screenshots.
Setup
They connected through CAST-1's fallback Wi-Fi hotspot, added it to Home Assistant through the ESPHome integration, and updated the firmware from there.
Music Assistant and multi-room sync
They streamed through Music Assistant to CAST-1 on a set of old PC speakers, then grouped it with a living room TV. They heard no audible drift between the two. A Google Nest speaker added to the same group played with a slight delay.
Announcements and text-to-speech
Using Piper for text-to-speech and a doorbell chime, they tested announcements over music. CAST-1 dropped the music by 40 dB for the announcement and faded it back in over about a second. See our TTS and announcements guide to set this up.
Ethernet
With the W5500 Ethernet HAT installed on its header, no soldering, CAST-1 switched to the wired connection. When they unplugged the cable, it fell back to Wi-Fi on its own.
What the review wants you to know
- No built-in amplifier. CAST-1 is a line-level source. Passive speakers need an amp.
- No Bluetooth audio input in the current firmware. Bluetooth on CAST-1 is for the Home Assistant Bluetooth proxy.
- The Ethernet HAT is not PoE. CAST-1 still needs USB-C power.
- Cables are sold separately. Bring a USB-C cable and a 3.5mm cable.
- Mixed groups vary. Sync with other Sendspin players was tight. A Google Nest speaker in the group lagged slightly.
CAST-1 specs
- Processor: Espressif ESP32-S3, 16 MB flash, 8 MB PSRAM
- DAC: Texas Instruments PCM5122, 32-bit stereo, 112 dB SNR and dynamic range, -93 dB THD+N
- Output: 3.5mm analog stereo line out, 2.1 VRMS full scale
- Playback: 48 kHz in the current firmware
- Network: 2.4 GHz Wi-Fi, or wired with the optional W5500 Ethernet HAT
- Bluetooth: BLE, Home Assistant Bluetooth proxy capable
- Power: USB-C, 5 V 1 A
- Extras: RGB status LED, plus solder pads for 5 V, GND, and IO1 to drive an LED strip that reacts to playback from the same device
- Size: 45 x 45 x 15 mm
- Firmware: open source ESPHome, Sendspin enabled by default
Full details are on the CAST-1 product page and in the CAST-1 wiki. Our CAST-1 launch post covers why we built it.
More CAST-1 reviews
SmartHomeScene isn't the only one. mostlychris showed how CAST-1 makes dumb speakers smart:
- Simon Says Home Assistant: Turn Any Powered Speaker into a Media Player with the CAST-1
- smarterkram (Olli, in German): a boombox music player for his youngest, with a volume limit and a four-button switch
For the ESPHome Starter Kit reviews from the same creators, see our Starter Kit review roundup.
Get started with CAST-1
- CAST-1 Audio Casting, $34.99 from Apollo Automation
- W5500 Ethernet HAT for a wired connection
- In Europe, from Domo-Supply (Switzerland) and Slim Huisje (Netherlands)
- CAST-1 getting started guide
- Music Assistant and Sendspin
- Apollo community forum
CAST-1 FAQ
What is the Apollo CAST-1?
CAST-1 is a small network audio player from Apollo Automation. It plugs into any powered speaker, soundbar, or receiver with a 3.5mm cable and streams music, announcements, and alerts from Music Assistant and Home Assistant. It runs open source ESPHome firmware and works 100% locally.
Is CAST-1 a Chromecast Audio alternative?
CAST-1 fills the same role Chromecast Audio did: a small box that turns speakers you already own into networked speakers. Chromecast Audio was discontinued in January 2019. CAST-1 runs locally with Music Assistant, Sendspin, and Home Assistant, with no cloud account.
Does CAST-1 work as a Google Cast or AirPlay receiver?
No. CAST-1 is not a Google Cast or AirPlay receiver. You send audio to it from Music Assistant or Home Assistant. Music Assistant can pull from services like Spotify, Apple Music, YouTube Music, TIDAL, and local files, and play them on CAST-1.
What is Music Assistant?
Music Assistant is a free, open source music server from the Open Home Foundation. It combines streaming services and local music into one library and plays it on speakers you already own, including CAST-1, Sonos, AirPlay, Google Cast, and Sendspin players. It integrates with Home Assistant.
What is Sendspin?
Sendspin is an open standard for synchronized whole-home audio, backed and governed by the Open Home Foundation. It runs on your local network with no cloud account, and keeps playback in sync across speakers. Music Assistant supports it natively, and CAST-1 has it enabled by default.
Can CAST-1 do multi-room audio?
Yes. Group several CAST-1 units, or CAST-1 with other Sendspin players, in Music Assistant for synchronized multi-room audio. In SmartHomeScene's test, CAST-1 grouped with a TV played with no audible drift.
Can CAST-1 play announcements and text-to-speech?
Yes. CAST-1 is a standard ESPHome media player in Home Assistant, so it handles text-to-speech, doorbell chimes, and alerts. When an announcement plays, the music ducks and then fades back in.
Does CAST-1 have a built-in speaker or amplifier?
No. CAST-1 has a 3.5mm line out and needs something to plug into, like powered speakers, a soundbar, or an amplifier. Passive speakers need an amp.
Does CAST-1 need Home Assistant?
No. CAST-1 works with Music Assistant, which can run on its own on a Raspberry Pi or home computer. Adding Home Assistant brings automations, announcements, and text-to-speech.
Does CAST-1 support Ethernet?
Yes, with the optional W5500 Ethernet HAT, which connects to a header with no soldering. CAST-1 switches to the wired connection and falls back to Wi-Fi if the cable is unplugged. The Ethernet HAT does not support PoE.
Does CAST-1 need the cloud or a subscription?
No. CAST-1 runs locally on your network with no cloud account and no subscription. Music streaming services you connect through Music Assistant still need their own accounts.
What DAC does CAST-1 use?
CAST-1 uses a Texas Instruments PCM5122 32-bit stereo DAC rated at 112 dB SNR and -93 dB THD+N, with a 2.1 VRMS full-scale line out. It runs on an ESP32-S3 with 16 MB flash and 8 MB PSRAM.
How much does CAST-1 cost?
CAST-1 is $34.99 from Apollo Automation. The optional W5500 Ethernet HAT is sold separately. A USB-C cable and a 3.5mm audio cable are not included.
Thank you
Thank you to SmartHomeScene for a thorough, honest review, and to the Music Assistant, Sendspin, ESPHome, and Home Assistant teams whose work makes a $34.99 box like this possible. If you put CAST-1 behind an old set of speakers, show us on the forum.
Apollo Automation designs, engineers, and manufactures privacy-first, locally-controlled smart home sensors in Versailles, Kentucky. Every product features 100% local control with no cloud dependencies or subscriptions required. Apollo is a Works With Home Assistant partner, Made For ESPHome certified, Works With Homey certified, a BBB Accredited Business, and the second official commercial partner of the Open Home Foundation. Learn more at apolloautomation.com.
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