Hey everyone, I’ve been tinkering with Home Assistant lately and stumbled upon a really cool way to sync my old IR stereo amplifier with the Chromecast volume controls. It’s been a game-changer for me! 
The Problem: My TV sends audio to the stereo via an optical cable, but the volume doesn’t sync automatically. Before, I had to fiddle with the IR remote or blaster every time. Such a hassle!
The Solution: I managed to link the Chromecast volume to my stereo using a Broadlink IR blaster and some clever automation. Here’s how I did it:
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Create a Volume Sensor: I set up a YAML template sensor that tracks the Chromecast’s volume percentage. This acts as the source of truth for volume changes.
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Derivative Helper: I used a derivative helper to detect volume changes. A positive derivative means the volume is increasing, while a negative one means it’s decreasing. This helps trigger the right actions.
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Automations: I set up automations based on the derivative values. For example, if the derivative is between 3-6, the stereo volume increases by a lot. If it’s between 0.01-1, it increases just a little. The same logic applies for decreasing the volume. This ensures smooth and proportional volume control!
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Mute/Unmute Automation: I added another automation to mute the stereo when the volume hits 0% and unmute it when it reaches 100%. Perfect for seamless transitions!
The Result: Now, I can control the stereo volume directly from my phone or PC while casting music or videos. It’s like having a smart stereo without upgrading hardware! 
Tips for Others:
- Make sure your IR blaster is properly calibrated for your stereo.
- Test the volume steps to ensure they match your listening habits.
- If you encounter lag, tweak the automation thresholds for smoother performance.
I’m really happy with how this turned out. It’s a great example of how smart home tech can breathe new life into old devices. If anyone has questions or wants to share their own setup, I’d love to hear from you! 