Just to clarify:
You can order the Isabellina HPA with "fixed" RCA outputs, or "variable" RCA outputs.
FIXED - For this option, the output from the Isabellina dac gets fed directly to the RCA outputs. This is a 2Vrms fixed output that you can feed to another headphone amplifier, or home audio preamplifier, or home audio integrated amplifier. In this configuration, it works exactly like the stand-alone Isabellina dac:
Red Wine Audio Isabellina
VARIABLE - For this option, the output from the Isabellina dac passes through the volume control before passing to the RCA outputs. This option is great if you plan to feed your Isabellina HPA directly into a home audio power amp. The volume control is like a "passive preamp" (no voltage gain). Most power amps can be driven to full output power with 2Vrms.
-- I suspect that the majority of you will go with the FIXED outputs, but there might be some of you who want to also use their Isabellina HPA connected directly to a home audio power amp and the VARIABLE feature is perfect for this.
-- What is stated above applies for the RCA output jacks. Some of you who are only using the Isabellina HPA as a headphone amp will not even care about the RCA output jacks (but you might down the road, especially if you want to integrated your Isabellina HPA into a home audio system, or use it as a dac to feed a different headphone amplifer).
Hopefully eveything is clear on this...
Vinnie