Thanks for the follow-up, @4425. Running balanced into the amp and unbalanced into the sub will result in a very slight imbalance between the impedances of the two signal lines in the balanced signal pair, relative to ground. That will result in a slight degradation of the ability of the amp to reject common mode noise that may be present at its inputs. I’d be surprised, though, if they would consider that effect to be great enough in degree to be audibly significant, since those impedances will be dominated by the output impedance of the preamp, which is vastly lower than the 50K unbalanced input impedance of a JL sub.
Or perhaps they were envisioning the possibility of ground loop issues. But that would be a possibility, depending on the specific designs, even if the unbalanced outputs were being used to drive a power amp and the balanced outputs weren’t used at all.
Those are the only two reasons I can think of that might lead them to recommend against driving a sub having suitably high input impedance with the preamp’s unbalanced outputs, while driving the power amp balanced.
Tketcham’s post reminds me that another member here who uses ARC Ref electronics and a sub had a tube buffer stage custom made for him some years ago by Tom Tutay of Transition Audio Design in Florida, which worked out very nicely and didn’t cost a great deal (well under $1K if I recall correctly). I don’t think Tom has a website but his contact info can be found via Google.
It sounds like you’ve settled on a course of action to which none of this applies, but I’m mentioning these things in case others find themselves in a similar situation.
Best regards,
-- Al
Or perhaps they were envisioning the possibility of ground loop issues. But that would be a possibility, depending on the specific designs, even if the unbalanced outputs were being used to drive a power amp and the balanced outputs weren’t used at all.
Those are the only two reasons I can think of that might lead them to recommend against driving a sub having suitably high input impedance with the preamp’s unbalanced outputs, while driving the power amp balanced.
Tketcham’s post reminds me that another member here who uses ARC Ref electronics and a sub had a tube buffer stage custom made for him some years ago by Tom Tutay of Transition Audio Design in Florida, which worked out very nicely and didn’t cost a great deal (well under $1K if I recall correctly). I don’t think Tom has a website but his contact info can be found via Google.
It sounds like you’ve settled on a course of action to which none of this applies, but I’m mentioning these things in case others find themselves in a similar situation.
Best regards,
-- Al