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Is that your interface with the highly modified power architecture?
Do you have an easy way to find that set of postings again to review? Maybe one of the changes has either decreased input CMRR for some reason, or has disconnected some of the audio circuitry reference from chassis, so that when the shield is connected to the reverb tank and the audio interface pin 1 or sleeve connection, that isn't effectively tying it to the circuit reference node.
The second would be my guess since the interface is running on batteries now.

Even high quality input designs have finite CMRR, and if the entire tank assembly is floating there will be some amount of power line noise induced onto the chassis through inductive or capacitive coupling. If the audio circuit ground does not have a connection to chassis to keep the common mode differences small then you can end up with a common mode signal so large there is no way the input circuitry can fully reject it.

<blockquote data-quote="ccaudle" data-source="post: 1124414" data-attributes="member: 41159">Is that your interface with the highly modified power architecture?&nbsp; Do you have an easy way to find that set of postings again to review?&nbsp; Maybe one of the changes has either decreased input CMRR for some reason, or has disconnected some of the audio circuitry reference from chassis, so that when the shield is connected to&nbsp; the reverb tank and the audio interface pin 1 or sleeve connection, that isn&#039;t effectively tying it to the circuit reference node.The second would be my guess since the interface is running on batteries now.Even high quality input designs have finite CMRR, and if the entire tank assembly is floating there will be some amount of power line noise induced onto the chassis through inductive or capacitive coupling.&nbsp; If the audio circuit ground does not have a connection to chassis to keep the common mode differences small then you can end up with a common mode signal so large there is no way the input circuitry can fully reject it.</blockquote>

[QUOTE="ccaudle, post: 1124414, member: 41159"] Is that your interface with the highly modified power architecture? Do you have an easy way to find that set of postings again to review? Maybe one of the changes has either decreased input CMRR for some reason, or has disconnected some of the audio circuitry reference from chassis, so that when the shield is connected to the reverb tank and the audio interface pin 1 or sleeve connection, that isn't effectively tying it to the circuit reference node. The second would be my guess since the interface is running on batteries now. Even high quality input designs have finite CMRR, and if the entire tank assembly is floating there will be some amount of power line noise induced onto the chassis through inductive or capacitive coupling. If the audio circuit ground does not have a connection to chassis to keep the common mode differences small then you can end up with a common mode signal so large there is no way the input circuitry can fully reject it. [/QUOTE]

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