SE vs Balanced volume

" Forgot to include in the original post that the tube amp is definitely fully balanced. Can the attached photo help determine if the SS amp is also?"

Look at the specs for both pieces. If a component is fully balanced, they list 2 sets of specs. One for SE operation and one for balanced. If 2 set of specs are listed, there should be a 6db difference between the 2. The balanced specs will be the larger number.

Sorry Al. You put your last post up while I was typing mine, so I didn't see it. You're much better at explaining this type of thing than I am, so I'm sure you would have had to clarify some of my posts anyway.

"So what your saying then is the RCA input uses the IN134 to provide an extra 6db of gain to keep both inputs the same level, but there’s no feedback network to set the gain, and as the data sheet says it’s fixed gain at unity."

No. The IN134 is not used to get an extra 6db. If you have a fully balanced component that needs to work with other single ended gear, you need to configure it to do so. Think of it as an adaptor. Also, you can't run a fully balanced component SE and Bal at the same time. The circuitry changes. You can't just use 2 pins of an xlr connector to make a SE connection. The pins do different things. If you've ever seen a component that has a little jumper connecting 2 pins of an xlr cable, that's why.

"Also then wouldn’t the switch have to have to be more than just a simple two pole switch? "

Since there's only 3 signal path/pins for balanced, the only change you can make is a simple 2 way switch. You're going from 3 pins to 2.

"If not then and I’m wrong the rca is at a disadvantage having to go through the opamp."

Correct. The opamp is another component in the single path, so it has to have some effect. In many cases, though, the complete opposite is true. If you have a singled amp but want it to work with balanced cables, the opamp is used on the xlr and not the rca.