Can a rogue audio Cronus be used just as a preamp?

I just looked at the owner's manual for the Cronus and it shows 2 sets of RCA outputs. 1 fixed and 1 varible, so yes you can use this as a preamp. Use the varible outputs so that the volume control works.

Seems like total overkill to use a tube amp for preamp duties. Sell it and buy a used Rogue Metis or VTL preamp assuming you want a remote.

Rogue Audio also offers an upgrade of the Cronus to the Magnum for a very reasonable price of $650. Along with other sonic advantages, this would almost double output from 55 WPC to 90 WPC. It would be tough to get a comparable second external amp at this cost point.

http://www.rogueaudio.com/The_Magnum_Series.htm#GeneralFeatures

Best,

Can I buy a 200 Watt plus outboard amp and use the Cronus as a preamp only?

No, you can't! At least without connecting load resistors to the speaker outputs of the amp. And the resistors would have to be rated to handle high power levels, and should also be a non-inductive type.

The reason is that operating a tube amp that has output transformers without a speaker load, or equivalent, can and probably will ultimately damage the output transformers and/or the power tubes, due to a phenomenon called "inductive kickback." Google that term for more information, if you wish.

The risk is particularly severe if music signals are going through the output stage of the amp while no load is present, which would be the case here since the design does not provide removable jumpers between the preamp and power amp sections of the unit. But it would be an unhealthy idea even with no signals present, because inductive kickback could still occur as a result of turn-on and turn-off transients.

Regards,
-- Al