Hi @RobCJohnson, thank you for reaching out to us and welcome to the Sonos community. I’d be happy to help you all here, let me ask some questions to isolate the issue so we can create a path towards resolution.

Can you tell me how is your Tannoy subwoofer connected to your Sonos Amp? 
What other music source connected to your Amp? 
Do you have other Sonos devices?

I'd appreciate if you can submit a diagnostic report of your system for better understanding and see what would be best for the setup. Reply to us with the confirmation number. We and the community are always here to help.

Hi

my subwoofer is connected via rca Jack in the left channel of the sun to the sun output on the amp )everything was working fine before switching my connect amp for the new amp.

The only other component I have on the system is the Sonos port.

Diagnostic report number is 1439834832

thankyou 

Hi @RobCJohnson, thank you for your response and for providing the diagnostic report. Let me help you out with this.

This is to clarify that your Tannoy Sub is wired via RCA to the Sub port output on the Sonos Amp. In the report, the Sub was detected and your Sonos Amp is also connected to your TV via HDMI cable at the same time.

Sonos Amp has an auto-detecting RCA subwoofer output with a user-adjustable 50-110 Hz crossover. Simply connect your subwoofer to the Amp’s RCA output labeled SUB. Please note that the subwoofer output is disabled when Amp is being used to power surround speakers for a Sonos home theater product.

To test the Sub, please disconnect the HDMI cable from the Sonos Amp.

If you have any questions about this. We and the community are always here to help.

Hi

The only connections to the amp are for left and right speakers and the subwoofer. There is no HDMI connection to a TV. So everything is connected as you have suggested. I really don’t know where the HDMI connection is coming from as there is certainly not one.

Hi 

Further to my previous message I have found out that the Amp is connecting wirelessly to a tv in another room as it shows up on the tv menu. 

Hi @RobCJohnson, thank you for your quick response. My apologies for the confusion. I've overlooked that there's no HDMI connected with the Sonos Amp. and I appreciate you for letting us know about it.

Based on the diagnostic, the Sub was detected as connected to your Sonos Amp. This means that it should work. You can perform basic troubleshooting to address this. 

1. Check if the RCA cable is not bent or kinked and check to see that it’s fully inserted into both devices.
2. If you can connect your Sub to another 3rd party device to check if it works using the same RCA cable.
3. User another RCA cable.

If you're still having the same issue after performing the steps above, I recommend contacting our Sonos Customer Care support to perform in-depth troubleshooting to isolate if the issue is with the Sub or with the Sonos Amp. 
Our phone support has the tools to check what's going on in your system and to remotely access your device to provide the best option for you.

Please feel free to reach out in the future if you have any other questions. You're always welcome here.