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As is usual for RWA gear, the innards are mostly empty and with what's there, the battery takes up most the space.

There are four boards to handle remote volume control, headphone output, D/A conversion and battery management.

For coupling duties, Vinnie Rossi has chosen the popular but expensive oil-impregnated metallized polypropylene units from VCap. Those take a long time to break in so don't judge this amplifier prematurely. Here is the HPA board for the remote-controlled Alps pot.

Here is the solid-state Isabella headphone output stage.

Here is the same board from the front with the coupling capacitors. "The headphone output driver stage is on a chip but not an opamp.  You cannot swap it for another 2-channel opamp because it has a totally different pin configuration. It is really a smaller 'chip amp' (think gainclone)*. It is a NOS part out of production for a while but I really love the sound and it can even handle 8-ohm loads - just don't expect to drive home audio speakers unless they are very efficient. In the Isabella preamp, we set the gain of the headphone stage to unity just as a buffer because the gain derived from the tube preamp stage. With the Isabellina HPA, it is configured to have greater than unity gain. As you can see, the board layout of the headphone stage has been cleaned up quite a bit but is essentially the same circuit."


* I do think this is semantics. The gain clones use National Semiconductor op amps in their output stages and have no qualms calling a spade a spade and an op-amp an op-amp (regardless of its pin configuration or last date of manufacture).

Here is the Isabellina D/A converter board. Vinnie itemized its highlights as follows:
  • New-old-stock 16-bit non-oversampling/non-upsampling D/A chip that implements R-2R conversion
  • No digital filtering
  • Proprietary discrete Class A transistor output stage without opamps
  • SLA battery powered with dedicated linear voltage regulators for the analog and digital sections
  • Highest quality parts and short signal paths throughout
"USB is converted directly to I-squared-S without intermediate conversion to S/PDIF. Unlike many DACs today which boast impressive specs but are flawed with an analytical, cold and sterile sound, the Isabellina DAC offers a natural and emotionally involving musical presentation that pulls the listener into the music and does not let go."

Here is the SMART module which constantly monitors battery charging to optimize life expectancy. "Isabellina HPA features our new SMART 1224 board which has been developed to be universal in that it can be configured to output 12V or 24V. SMART 1224 monitors battery voltage and automatically switches the unit off if voltage falls too low and then automatically triggers the charging process via the external charger.  It also completely isolates the charger (both the + and – connections) from the unit when it is turned on to run exclusively on SLA battery power. Beyond managing multiple voltages (SMART 1224 is also used in the Black Lightning units), the new board incorporates a micro controller and our proprietary firmware to manage internal processes. Greater responsiveness in Red Wine Audio’s unique on/off switch is where this upgrade is most evident to end users. Now the red diode on the power switch begins to slowly blink when the battery voltage is getting low. SMART 1224 also features 0.5 second in-rush current limiting to provide sensitive audio gear with a soft start to prolong the life of internal components."

About pricing, Vinnie Rossi explained that "at $2,500, the Isabellina HPA assumes the price point originally held by the Isabellina in DAC form only. Isabellina's’s pricing as a stand-alone DAC has been lowered to $2,000 and a new version of the Isabellina sans USB input is now available for $1,500."

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