Biggest impact: moving from integrated to separates

@asp307
If the output impedance of the line stage is 10K or less at all audible frequencies, **or** if the output impedance doesn't vary very much over the frequency range even if it does exceed 10K, there won't be an impedance compatibility problem with a 100K load.  It would be very rare for a line stage to not meet the first of those criteria, much less both of them.

Regards,
-- Al

@asp307

they said 100K

OK, if so you won’t have an impedance compatibility problem connecting any reasonably designed line stage to the variable outputs.

That would certainly explain, though, why they added a buffer stage for that output in the Magnum II version. A 100K output impedance would be pretty much useless for driving many and perhaps most powered subs, which commonly have line level input impedances in the area of 5K to 20K. And in an application where treble response may be important, such as using the variable outputs to drive a separate amplifier for biamping, the resulting sensitivity to cable capacitance would be very likely to cause poor results as well.

Good luck. Regards,
-- Al

Asp307, has there been any word from Rogue on the output impedance of the variable output?

BTW, for those who may own a Cronus Magnum II, I found the following statement in a description of that version of the amp at a dealer’s site:

The Cronus Magnum II comes with a host of upgrades over the original Magnum.... The variable outputs are now buffered for better subwoofer performance....

Assuming the buffer which is referred to is an active buffer, which it almost certainly is, I would caution anyone owning a Magnum II that Rogue’s suggestion to the OP that it would be ok for him to connect the output of a line stage to the variable output of his earlier version of the Magnum will not work with the Magnum II. And although it is probably unlikely, doing so could conceivably even cause damage, depending on the specific design of the line stage and the Magnum II’s buffer.

Regards,
-- Al

Awesome! Thanks for letting us know.

I would suggest, though, that you follow up with him by asking what the output impedance of the variable output is. Assuming that the "variable output" is in fact an output, that output impedance will be seen as a load by whatever line stage you connect to it. Which in turn could very conceivably result in an impedance match with the line stage you end up choosing that is very non-optimal from a sonic standpoint. Especially if the line stage you choose has a coupling capacitor at its output, as most tube-based line stages and at least a few solid state line stages do.

Also, when and if you use this approach I would suggest having the CM’s input select switch set to something other than phono. And in addition it would probably be a good idea to put shorting plugs on the selected input, to avoid the possibility that RFI/EMI pickup might cause the CM’s line stage to sum a low level "signal" together with the intended signal. If you search at eBay for "RCA shorting plug" (without the quotes) you’ll find many such things at very low prices.

Good luck. Regards,
-- Al

asp307 12-19-2017
I am not looking to upgrade both amp and line stage at this point, just one or the other with the next upgrade probably occurring next year. I can continue using the Cronus Magnum either as a line stage or amp so I have flexibility.

If I’m not mistaken none of the versions of the Cronus Magnum provide either an input to the amplifier section or a means of disabling the amplifier section.

Which means that if you were to use it as a line stage you would have to put load resistors having high power handling capability onto its speaker output terminals. As you may be aware, running a tube amp which has output transformers in an unloaded condition can cause damage to both the transformers and the output tubes, especially if the amp is processing a signal.

And if you were to use the CM as an amp, I believe you would have to have its line stage in series with the new line stage you would be purchasing. That would work, but it would probably negate the benefits of the upgrade. Although I realize it would only be a temporary arrangement.

Good luck. Regards,
-- Al