"i am actually considering the Dartzeel NHB-18NS but i was told that the XLR outputs are not at the same level as the single ended ones."
John Atkinson, test of above preamp published in Stereophile:
"Turning to the NHB-18NS’s line-stage performance, I looked first at the balanced input. Measured at the balanced outputs with the input set to "Pro," this gave a maximum gain of 9.3dB. Switching in the –6dB input pad gave 4.85dB. Absolute polarity was preserved, indicating that the XLRs are wired with pin 2 hot. The input impedance was an extremely low 640 ohms, while the output impedance was a high 2500 ohms at low and midrange frequencies, rising to 3080 ohms at 20kHz. The input impedance is too low for many source components to give their best performance, the output impedance a little high for some power amplifiers.
The balanced input’s frequency response didn’t vary with different settings of the volume control, but it did peak by 0.75–1.25dB at 42kHz before precipitously rolling off (fig.3, top pair of traces). The audioband response was flat with the input switch set to "Pro," but with the input set to "–6dB," a –0.75dB trough appeared in the treble (fig.3, lower pair of traces). A glance under the preamp’s cover told me that the balanced input and output appear to be realized with transformers, which are presumably the cause of the response anomalies. Even so, I don’t feel the DarTZeel’s balanced inputs and outputs to be of much practical use, the unbalanced jacks being better behaved."
Read more at
http://www.stereophile.com/content/dartzeel-nhb-18ns-preamplifier-measurements#d1Fd12jf0zGKjyAS.99This confirms what you heard as well as this preamp’s incompatibility with other brands of amps (and sources) using XLR inputs/outputs as stated by the manufacturer.
I would look elsewhere, thieliste.
Dave
