Emerson -- Yes, thanks for reminding me of our conversation about the Blue Jeans cables, which have an extremely low capacitance of 12.2 pf/ft. So I don't think you've got any problem in terms of capacitive loading. Even if you were to have three twenty foot cables loading the same preamp output, their combined capacitive impedance ("reactance") at 20KHz (the worst case frequency) would be around 11,000 ohms, according to my calculations.
However, if the subs really have a 6,000 ohm input impedance, and especially if the VTL 2.5 doesn't separately buffer the two outputs, you've definitely got a problem there.
If there are not separate buffers, the preamp would see a load impedance consisting of 6K, 6K, and 10K in parallel, which is about 2.3K (the reciprocal of the sum of the reciprocals of the three numbers). If there are separate buffers, and if you had one of them driving the two subs, that output would see a load of 3K. Or if you had one of the subs connected to the same output that drives the DNA-500, that output would see a load of 3.75K. All of these numbers are most likely too low to be acceptable.
Let us know the make and model number of the sub, and perhaps one of us will be able to find a definitive indication of its input impedance. And perhaps check with VTL to find out if the two outputs are separately buffered (or if convenient, remove a cover which would allow you to see if the two output jacks for each channel are simply wired together, or if they appear to be coming from separate circuit points).
Regards,
-- Al
However, if the subs really have a 6,000 ohm input impedance, and especially if the VTL 2.5 doesn't separately buffer the two outputs, you've definitely got a problem there.
If there are not separate buffers, the preamp would see a load impedance consisting of 6K, 6K, and 10K in parallel, which is about 2.3K (the reciprocal of the sum of the reciprocals of the three numbers). If there are separate buffers, and if you had one of them driving the two subs, that output would see a load of 3K. Or if you had one of the subs connected to the same output that drives the DNA-500, that output would see a load of 3.75K. All of these numbers are most likely too low to be acceptable.
Let us know the make and model number of the sub, and perhaps one of us will be able to find a definitive indication of its input impedance. And perhaps check with VTL to find out if the two outputs are separately buffered (or if convenient, remove a cover which would allow you to see if the two output jacks for each channel are simply wired together, or if they appear to be coming from separate circuit points).
Regards,
-- Al