Damn I'm old... Can't figure out the tape loop on a Bryston SP3

Call your dealer. That's what they're for.

Tape (or processor) Loop, you go out to your deck or processor, and back to Tape IN. On older Preamps, there is a 'Monitor' or some similarly named switch that selects the tape loop input (doesn't matter what your source selector is using, it cuts to the tape input automatically).

this unit?

https://schroederamplification.com/products/bryston-sp3-surround-preamplifier

Looking at the rear jacks, there are two tape loops, one analog and one digital. It has to be selectable, and other settings are involved to get to 2 channel, etc.

here's your manual, perhaps someone here understands these modern devices, not me.

http://support.bryston.com/downloads/sp3/documents/300024%5BSP3%5D.pdf

Try the Bryston forum.

https://support.bryston.com/forum/29/

It looks too complicated for me.For the bucks the manual should be clear.

"It looks too complicated for me.For the bucks the manual should be clear."

Haha, my thoughts exactly!!

What’s not clear??

4: TAPE RECORDER TAPE LOOP A conventional tape loop consisting of two pairs of RCA jacks; one stereo pair of inputs and one stereo pair of outputs. A stereo down-mix for the selected source (or, in 2 Channel Bypass mode, the Left and Right analog inputs directly) appear at the TAPE OUTPUTS, unless the selected source is the TAPE INPUT itself in which case the TAPE OUTPUTS are muted. The inputs can, of course, also be used as just another pair of analog inputs, but at unity gain only & no volume control.

It is NOT a tape LOOP.  It has parallel tape monitoring outputs and tape inputs to listen from tape.  But it does not have a tape LOOP where you can send signal out the tape outs and receive back into the tape INPUTS simultaneously..  The term LOOP is a misnomer...  You can NOT insert an BAF/EQ in that loop.