Isabella Vacuum-tube Preamplifier
LiFePO4 battery now included »
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. We 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, low-resistance 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 that matches our award winning Signature 30.2 and Signature 70.2 amplifiers. 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 visibility
- Separate linear voltage regulation stages for B+, tube heaters, input select relays and optional DAC
- 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 (Seamless battery Monitoring and Auto Recharge circuiT). This is a custom-designed circuit board that continuously monitors the voltage of the internal batteries. If the voltage drops too low, the SMART module automatically turns off the Isabella and begins the battery recharge process for you.
Battery / AC power mode selection switch
The Isabella also features a switch to allow for continuous operation from the external 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.
Options
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. We 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)
- 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 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.
Shown with optional built-in Isabellina d/a converter
“The Isabella has the most musical sound I’ve yet to experience when feeding from a source via USB.”
Jeff Dorgay, TONEAudio
Isabella headphone output stage
For the headphone connoisseur seeking the ultimate listening experience, we offer the Isabella with an optional, built-in headphone output stage. The result is truly a unique, audiophile battery powered tube headphone amplifier featuring input source selection, adjustable gain, remote volume control, and an optional built-in Isabellina d/a conversion module. 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!
“You will freak out over the quality of what lurks in the Isabella for a mere $500 upgrade. I’ve heard a lot of the best and most expensive headphone amplifiers now, and I’d put this one right at the top of the list, regardless of price!”
Jeff Dorgay, TONEAudio
Reviews
“Fleet of foot, compact, quiet, reliable and damnably low in coloration and seasoning, I’ve kept her around in preference to many a better known adversary. You’re gonna change amps; you’re gonna change wires- you’re gonna change speakers- hell, you’re an audiophile! So you owe it to yourself for once and all to have a centerpiece- a lynchpin- a piece around which everything else can turn. That’s Isabella!”
“For guts, fleshiness and wallop — in short, the illusion that the ghostly phantom images in your sound room have bodies and arteries with flowing blood — the Isabella delivers more than class leaders at twice her price.”
“The tonality of the Isabella is excellent. I firmly believe this is due to the lack of grain from power supply artifacts coloring the signal.”
“The Isabella [combined with the Signature 30.2 power amp] will be tough to beat without spending a lot more money.”
“…few preamps in my experience combine quietude, transparency to source, PRaT and tonal veracity with fuss-free operation and friendly, non-Machiavellian designers in quite the way Isabella does.”
Specifications
Optional Isabellina DAC 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, 1,500mA 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 (without charger) |
Approx. 15 lbs. |
Package weight |
Approx. 20 lbs. |
Proudly manufactured in the State of Connecticut, United States of America
Product design and specification subject to change or modification without notice.
Purchase
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International Customers »
Limited Warranty »