From the measurements section of Stereophile’s review of the BAT VK-51SE:
Which means that this preamp is not compliant with the AES48 requirements Ralph has described. It also means that it would not be a good match for the 20K load it would see when connected to both amps, assuming (as is highly likely) that its two balanced outputs are driven by the same output stage.
Best regards,
-- Al
The balanced output impedance was twice that specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20Hz, due to the size of the output coupling capacitors.
Which means that this preamp is not compliant with the AES48 requirements Ralph has described. It also means that it would not be a good match for the 20K load it would see when connected to both amps, assuming (as is highly likely) that its two balanced outputs are driven by the same output stage.
Best regards,
-- Al