How do I reset a Marantz sr6007 to factory reset

Hi Mark,
One can hook-up as many peamps as desired to the SR6007 either as sources or destinations. How to connect external preamps to the SR6007 depends on what you wish to achieve.
The SR6007 already has its own internal preamps.
You could, if you are not careful, burn the AVRs input circuitry by adding external preamps as "sources". Also, not much improvement in SQ could be gained by external preamps connected to the SR6007's preouts becuase any signals that come out of these have already been processed (or distorted?) by the SR6007s internal preamps.

If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
Search the site by type in the "Brand Name" (Exclude the model number) to your device, in the "Search box at the top right of the display window of the Homepage" to get gathered related posts.

Reset to factory and make sure you have a good network wifi signal before starting a firmware upgrade. The reset is listed on the last page of the troubleshooting section of the manual. (Surround + Clear for 3 Seconds on my SR6004)

Hope this helps: How to reset the SR6006
Microprocessor reset (p. 150 Owner's manual) - Press and hold the Zone Select/Display buttons while powering on the AVR ......release 4-5 seconds later

Network reset - Press and hold the M-Dax/Display buttons (resets network card and does a microprocessor reset)

If you need further help, reach me via phone at https://www.6ya.com/expert/timothy_c6f309c0f75b6f43

Try to reset to your Marantz to factory settings, or try the newest Firmware. :)

how to factory reset marantz sr5007

Hold the 'display' and 'zone select' buttons, then press power. Display should blink all segments. Let go of buttons, and your good to go