RedWineAudio Isabella with DAC + headphone output stage

Introducing the Red Wine Audio Isabella - a reference-level, battery powered vacuum tube line-stage preamplifier created for music connoisseurs seeking a sublime listening experience, dependability, and value. Meticulously designed the Isabella to greatly enhance any high quality two-channel music system by offering the listener an emotionally involving, natural, and effortless musical presentation.

The heart of any line-stage preamplifier is its power supply, and the Isabella's heart is pure using high-current sealed lead-acid (SLA) batteries that allow all the nuances of the music to emerge with remarkable integrity. Because the Isabella uses no transformers, rectifiers, power cords or any form of dependence on the AC power grid during playback, the Isabella frees your music from the entire AC to DC conversion process and the associated electrical noise and hum problems that hinder the performance of conventional vacuum tube line-stage preamplifiers.

Inside the Isabella is a unique design that reflects our philosophy in using carefully selected and tested premium parts, short signal paths, and going "off-the-grid" with battery power. On the outside you will enjoy simple yet elegant aesthetics and superb build quality. Every Isabella is proudly hand-made in the USA and carefully tested, inspected, and packaged before making its journey to our highly-valued and satisfied customers.

Features

• Two 6922 dual triode tubes (one per channel)
• 3 sets of analog inputs and 2 sets of analog outputs using premium Vampire RCA jacks
• Remote volume control using motorized Alps potentiometer
• Hi/Low gain select switch to maximize volume control range in various systems
• Sliding glass window on top cover for easy tube access and visability
• Separate linear voltage regulation stages for B+, tube heaters, input select relays and optional dac (see below)
• Only one premium paper-in-oil capacitor in signal path
• No transformers, no rectifiers, no DC-DC converters, no ribbon cables or connectors in the signal path
• Auto-mute delayed turn-on sequencing (approx. 40 seconds) to allow for adequate tube warm-up and stabilization and to eliminate turn on/off transients

SMART module equipped

The Isabella features a Red Wine Audio innovation - the SMART module (SLA battery Monitoring and Auto Recharge circuiT). This is a custom-designed circuit board continuously monitors the voltage of the internal SLA batteries. If the voltage drops too low, the SMART module automatically turns off the Isabella and begins the battery recharge process for you.

With the SMART module, any user concern of accidentally damaging the internal SLA batteries by forgetting to turn off the Isabella is eliminated.

Battery / AC power mode selection switch

The Isabella also features a switch to allow for continuous operation from the external SLA battery charger for "non-critical" listening such that the battery charging and listening can occur simultaneously. While running direct from battery power offers cleaner power, blacker backgrounds and no chance of ground loop hum, we added in significant filtering to the external power input to ensure listening in this mode still results in excellent sound.

Isabellina: built-in, digital-to-analog conversion module

The built-in “Isabellina” dac module recreates music from digital media as close as possible to that of a high-end analog setup. Carefully voiced the Isabellina to seduce the listener with a non-fatiguing sound conveying the indisputable qualities of analog playback, such as richness of tone, excellent pace/timing, spaciousness, and natural upper frequency resolution.

Our recipe is a purist approach:

• New-old-stock 16-bit, non-oversampling/non-upsampling D/A chip that implements R-2R conversion
• No digital filtering
• Discrete Class A transistor output stage (no opamps)
• SLA battery powered with dedicated linear voltage regulators for the analog and digital sections

The Isabellina option provides three digital inputs that are selectable on the front panel of the Isabella tube line-stage preamplifier (along with the three analog line-level inputs):

- USB that converts directly to I2S to feed the dac chip (no intermediate s/pdif conversion). This input offers optimal sound quality and requires the use of a computer (music server) with a USB port. The power bus from the computer is not used. We instead provide our own clean, on-board +5V line derived from SLA battery power.

- Coaxial (s/pdif) with a Vampire 75-ohm, high-bandwidth BNC jack followed by a digital pulse isolation transformer that isolates noise from the source and gives precision 75-ohm impedance matching.

- TOSLINK (optical s/pdif) that naturally offers noise isolation and avoids ground loops from the source via the optical transmission cable.

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Isabella headphone output stage

For the headphone connoisseur seeking the ultimate listening experience the built-in headphone output stage is the last stop for headphone excellence. The result is truly a unique, audiophile battery powered tube headphone amplifier featuring input source selection, adjustable gain, remote volume control, and the built-in Isabellina d/a conversion module (see above). Simply connect your finest pair of headphones to the 1/4" stereo jack added to the rear panel (providing the shortest signal path) and become emotionally connected with your music in a whole new way!

Technical Specifications

Included Tubes	6922/E88CC dual triode (one tube per channel)
Accepted Tubes	6922/E88CC, 6DJ8/ECC88, 7308/E188CC, 7DJ8/PCC88, 6N23, 6H23, and 6N11
Input Impedance	50k
Output Impedance	Less than 1k
Frequency Response	10Hz - 120kHz (+/- 0.5 dB)
Gain	0dB / 12dB (selectable)
Power supply transformer / rectifiers / transformers in signal path	None
Batteries	2 x 12V, 5Ah Sealed Lead-Acid (SLA) batteries connected in series (24V system)
Battery charger	Rapid-speed, 24V, 2,000mA SLA "Auto-Charger," custom-modified for use with Red Wine Audio SMART module. Universal input voltage (100 – 240Vac, 50/60Hz), IEC power input jack, and output cable featuring a heavy duty XLR plug.
Typical play time between full battery charges	Approx. 6 to 8 hours in battery mode / Continuous playback in AC power mode (see above for details)
Dimensions	12” width x 10.5” depth (including volume knob and rear panel jacks) x 3.5” height (including feet)
Weight (w/o charger)	Approx. 15 lbs.
Package weight	Approx. 20 lbs.