If you are looking for a preamp that has XLR inputs and outputs, you might want to know that many products in high end audio, even though they have balanced XLR connections, don’t actually support the balanced standard.
This is true of both the ARC and Aesthetix. As Al pointed out, one of the problems with this is that neither is a good combo with your Bryston on account of the low frequency output impedance. But that’s not all- another problem with not supporting the balanced standard (also known as AES File 48) is that the interconnect cables you use in your system will have to be auditioned for the best sound; IOW you will hear differences between cables, and that isn’t supposed to happen!
The balanced standard is supposed to eliminate interconnect cable differences. To this end, it has a benefit whether the cable is 6 inches or 60 feet.
You can always ask the manufacturer about whether their equipment supports the standard, but one clue that it doesn’t is the use of output coupling capacitors. I don’t know of a topology that allows for their use. The reason is that part of the standard is that ground (in other words, the shielding of the cable, pin 1) is ignored. Instead, the signal travels as a twisted pair within the cable, so the shield is only used for shielding and **not** signal current return. When there are signal currents within the shield, then the construction of the cable gets a lot more critical, i.e. the cable itself becomes audible, which defeats one of the intentions of the balanced system.
There are high end audio preamps out there, even tube preamps, that support the standard and have XLR inputs and outputs, and further are fully balanced from input to output.
FWIW, the Calypso is a way better preamp to my ears than the SP6!
