The Isabellina HPA combines the Isabellina DAC with the headphone amp that’s available as an option with the Isabella tube preamp. In addition to high-current SLA battery power with dedicated linear voltage regulators for both the analog and digital sections, the Isabellina HPA also features the Smart 1224 board, which monitors the battery voltage and automatically switches the unit off if the voltage falls too low. This board also features 0.5-second inrush current limiting, to prolong the life of the internal components.
The philosophy behind the DAC is a bit unusual in that a modern DAC chipset is not used. Rossi believes that even modern DAC chipsets boasting impressive specs sound cold, sterile, and analytical. His answer is to use a new-old-stock (NOS), 16-bit, non-oversampling, non-upsampling DAC chip with no digital filtering, which he claims offers a more natural sound, for a more emotionally involving musical experience. The analog output stage is a discrete class-A output with no op-amps.
Looks-wise, the Isabellina HPA is handsome in minimalist fashion, and mirrors the appearance of its sibling products. The casework is powder-coated aluminum with a nice nubby finish, and the faceplate is black-anodized aluminum. The front panel has a centrally located volume-control knob of silver-painted aluminum, flanked on the right by a 0.25" stereo headphone output jack, and on the left by a flush-mounted, soft-touch power button. On the power button is a red LED that blinks slowly when the battery voltage gets low.
On the center of the rear panel is a pair of vertically arrayed RCA line-output jacks. To their left is the jack for the battery charger, and to their right is a three-way toggle for selecting the digital input: optical (TosLink), coaxial, or USB. The USB input accepts sample-rate frequencies up to 48kHz, while the coaxial and optical inputs accept up to 192kHz.
The Isabellina HPA comes with a dedicated wall-wart charger and a handheld remote control. An optional 12VDC output ($100) is available for powering a Wadia 170iTransport.
At 12"W x 3.5"H x 9"D and weighing ten pounds, the Isabellina HPA isn’t really "portable," but it’s small and light enough to haul around in a padded duffle. My local coffeehouse and bakery has free WiFi, and I was tempted to take it there for some remote listening, but was too concerned about spilling coffee on something that didn’t belong to me to tempt fate. However, I was able to use it all over my house, and even ended up taking it to work.