December 2013

World Premiere!
Red Wine Audio Isabella Renaissance Edition Preamplifier
An impressive battery powered tube preamplifier for $3995.
Review By Tom Lyle

  This is the second battery-powered component I've had in my system within the last year; the previous was for a review of a rather nice DAC. This time instead of coming from a manufacturer that offers only one or two products that are powered by batteries, Red Wine Audio's complete line of preamplifiers, power amplifiers, and headphone amps run "off-the-grid" using LiFePO4 (lithium iron phosphate) battery power. One can only hope this is indicative of a general trend, as the advantages to eliminating the conversion of one's home AC to the DC current necessary to power audio components are many, and with the popularity of the type of lighter, more user friendly batteries that are used in Red Wine Audio products I hope that battery powered components will become even more popular.

Around
Run by the estimable Vinnie Rossi, Red Wine Audio has been around for about ten years, and still stands alone in offering a full line of battery-powered components. The subject of this review, the Isabella linestage, has proven a very popular product within their line, and has recently been upgraded to a Renaissance Edition that features a pair of 6H30 "super tubes". Red Wine claims that this new iteration of the preamp offers better sound, improved cosmetics, tube rolling options within the 6922 family, and the ability to order the preamp with an on-board Analogica phono preamp, Cassabria single-ended or balanced headphone stage, an internal Bellina DAC, and other options. Although I wouldn't go as far as calling myself a purist, I have chosen to review the Isabella preamp without any extraneous on-board amps or converters and will focus solely on the unit's preamplification functions.

First off, the Isabella is a handsome looking component. The rather small cabinet measures only 13.5" wide and 10" deep, but its good looks are in no doubt due to its handmade 0.5" solid-wood front and side panels, which are available in maple, walnut, or cherry and are hand-sanded between each of its multiple polyurethane applications. The front panel is laser-engraved, with chrome-plated aluminum control knobs. Red Wine is thoughtful enough to forgo attaching the Isabella's vented top plate with screws that need an esoteric driver head, instead using three thumb-screws. The Isabella's rear panel has RCA inputs for three sources, has two pairs of RCA outputs, and an XLR input jack for the provided charger's output cord (and an standard IEC power cord is plugged into the charger). The remote of the Isabella is a weighty aluminum affair that befits the stylish component. The remote's sole responsibility is to raise or lower the Isabella's motorized volume control.

When opening the top plate of the cabinet to expose the preamp's innards, there appears to be ample space for the optional DAC, phono preamp, or headphone amp. This totally handmade in the USA component's insides reflect the skill and design acumen that was necessary to build it: it is neatly laid out and appears meticulously constructed. The battery occupies about a third of the available internal real estate, which is quite amazing given the size of batteries that they would have had to use in olden days that would supply enough current for use in a preamplifier of this caliber. Besides their smaller size, these newer batteries have a much longer usable life between charges, not to mention that these newer batteries are a heck of a lot simpler to re-charge. The Isabella's front panel three-position rotary switch lets the user choose between: off and charging, on and charging, and a position where the preamplifier runs exclusively on battery power, leaving the wall's AC current totally out of the preamp's circuits. The battery life is claimed to be approximately eight hours. During the Isabella's residency it never ran out of power during any of my listening sessions. Red Wine Audio terms their battery management system SMART, Seamless battery Monitoring and Auto Recharge circuiT. This system automatically monitors the battery's power. When it gets low, it turns the preamp off and starts to charge the battery, and when it is fully charged, it is again ready to use. As I stated previously, the Isabella never ran out of battery power. Nor was it necessary to initiate this charging sequence, I simply let the battery charge while I wasn't using it, and every once in a while during play if listening off-axis. Red Wine Audio claims that the unit sounds better when the front panel control is in its third position, running exclusively on battery power, and I agree with them wholeheartedly.

Red Wine Audio suggested that I try out the selectable gain switch located on the rear panel that enables the user to select between a low and high gain setting. I suppose it's either because I have neither very sensitive nor very insensitive loudspeakers, so the gain control made not a whit of difference to the Isabella's sound. Yes, I needed to turn the volume control up more when I chose the lower of the two settings, but heard no sonic advantages of doing so. And I had no problem with the gain setting being sensitive enough to satisfy even on its lowest settings regardless of the gain setting. Your mileage may vary.

Audition
I usually audition a component such as the Isabella in one of my two systems, but this preamplifier was at home in either – the downstairs system in a common space powered by a pair of PrimaLuna tube monoblocks, or in the main rig in my dedicated listening room powered by solid-state behemoths, either a Pass Labs X350.5 or Maker Audio NL14+ monoblocks. The smaller downstairs system is where it spent most of its time, though, and where I spent the most time "seriously" listening to the preamp, with an all-digital front end consisting of a Logitech Squeezebox Touch feeding either Benchmark DAC1USB or Wadia 121 digital to analog converters. An Oppo BDP-83 Special Edition universal player's digital outputs were also connected to the same DACs, and the player's analog outputs connected directly to the Isabella preamp when spinning SACDs or the occasional DVD-Audio disc.

The 70 Watt per channel PrimaLunas powered a pair of EgglestonWorks Isabel (no relation) two-way floorstanders.  The system's cables were mostly DH Labs' Silver Sonic series, including the digital cable that connected the transports to the DAC. For a while the cabling was by the much more pricey Furutech cables that were on loan. The front-end and the preamp sat upon Metro Commercial shelving, and the room is untreated other than the normal household furniture and wall hangings one is likely to find in a suburban home. The room is relatively "live" sounding, but doesn't bother me at all since it tends to lean toward the neutral when the shades are drawn, which they are when I'm seated in the listen seat during any listening session where I am paying full time and attention.

On their website Red Wine Audio claims that the Isabella preamplifier will reproduce music with "great dynamics, tight resolved bass, and an open and extended treble". I don't know why I'm bothering you with this information. Is this claim made by every high-end audio manufacturer regardless of the type of component? Sure it is. Despite these assertions, I was awfully disappointed when I first connected this preamplifier. It took a good 50 hours before it even started sounding what any sensible audiophile should deem acceptable, as the system sounded as if someone installed some sort of filter and/or phase inverter into the chain.  Slowly it settled in. I sure wish all audio companies were somehow able to ship their equipment already burned in. And I also wish I hadn't judged the Isabella so harshly before I started paying such close attention to its sound. That's a tall order, especially since I regularly use this system for "background" music.  Regardless, I was relieved that the Red Wine Audio Isabella sounded so good once it was broken-in.

Lately, when I'm "between" preamps I've gotten into the habit of using this system's DAC in lieu of a stand-alone preamplifier. I have a good feeling that's what many are doing these days, especially since the dawning of the computer-music age. There's nothing wrong with using the variable output of a DAC as a substitute for a preamplifier if one has only digital sources. This makes sense – why interrupt the path of the signal with more than is absolutely necessary? There isn't much point going into the technical reasons of why or why not a separate preamplifier is a good idea, because in my system there is no doubt that a separate preamplifier sounds better in my system.  I've used some rather pricey DACs in this system, and yes, these DACs sound very good when used as a preamplifier, but it always has sounded better with the separate preamp.  Perhaps it is because I've always used a high-quality high-end tube preamp? Bingo.

Sounds
The Red Wine Audio Isabella preamplifier sounds great in my system. It doesn't sound great because it sounds very transparent to the source, although it does sound very transparent to the source. It doesn't sound great because it has an exceptionally deep and pitch-stable bass, although it does have an exceptionally deep and pitch-stable bass, especially if one considers that these frequencies are coming from a tube preamp. It doesn't sound great because Red Wine Audio's claims of having an extended open treble are spot on. The Red Wine Isabella sounds great because it has all of the above characterizes, and at the same time the instruments that pass through its circuits sound realistic. To me, this trait should be placed above all others. The Isabella's transparent midrange has more to do with this than anything else, I suppose, and all the other traits were icing on the cake as I enjoyed these realistic sounds enter my listening room.

I'm not sure what prompted me to put on King Crimson's Lizard album. It's one of their most misunderstood albums, and without doubt one of the least heralded from their prodigious early to mid-1970s period. I don't think it's because the lyrics are overwrought (they are) but even though there is plenty of Mellotron to be had, stylistically, it just deviated too far from the more straight-ahead progressive-rock of the first two albums. But this jazz-influenced album is a great analog multi-track album from this golden age, and the abundance of acoustic instruments makes for a memorable audiophile experience.  Plus, once one has listened to all their other albums from this period multiple times, this album makes much more musical sense. Over time it has become one of my favorites. On the first track "Cirkus (Including Entry Of The Chameleons)" we're treated to not only plenty of Mel Collin's sax, but other winds provided by the guest musicians invited to London's Wessex Sound Studios in 1970.  Leader and guitarist Robert Fripp puts on a fine display with more clean and acoustic guitar than on the previous Crimso albums, and his guitar is recorded well enough to add to the aural festivities. The Isabella preamp doesn't attempt to make more of this recording than is presented, the preamp's slightly warm sound only aids in making the acoustic instruments sound more authentic. The end results weren't as if the instruments and voices enter the room, but more of a clear window into the recording session.

The imaging and soundstaging prowess of the fine EgglestonWorks speakers of course are dependent on the associated equipment feeding them as the sound quality of the source, and the combination of the EgglestonWorks and the Red Wine Isabella made the album sound more "real" than it ever has. The man-made soundstage was wide and deep, and the images of the frighteningly realistic sounding flute, acoustic guitar, voice, and guest musician Robin Miller's cor anglais on the pastoral "Lady Of The Dancing Water" were rock solid, each find its place in the huge soundstage and their positions did not waver despite their varying pitches and volumes. I have reservations with calling this trait of the Isabella "imaging", as it went far beyond this. I feel more comfortable calling it instrument "placement", because that's what the Isabella did – it simply placed certain instruments in the soundstage where they belonged according to where they appeared on the recording. Instrument placement was certainly more realistically located on orchestral recordings or other types of music recorded in a real space, but that's not the point. The instruments on this studio recording are placed according to many factors, chief among them their volume and left/right panning, but still, the impression that I got was that I was listening to real people playing real instruments in a real space, even though that space was the recording studio.

Because the Isabella is battery powered, I expected it to have very little, if any background noise. Of course, it is also a tube unit, so I also expected that I would have had to allow for a bit of tube noise. I was wrong about that. The background of the Isabella was supernaturally quite. Not supernaturally quiet for a tube preamp, supernaturally quiet for a preamp, period. I'm lucky; I don't live in a particularly EMI/RMI rich neighborhood although I can't explain why – I'm about a quarter-mile away from a train station, and there are a number of commercial establishments nearby. But when I turn the preamp's volume control to 11 and put my ear to the speaker there is nothing, not even a hissing sound. Of course this is also due to the associated gear, especially the very quiet PrimaLuna tube amps. Even when I set the preamp to run from the wall current (while still charging the battery) the background of the Isabella was extremely quiet. Switching it to run off of the battery was a game-changer, though. Every sonic benefit that comes from having a quite background was amplified. The most valid comparison is live music, during events such as when one can hear the musician take a breath before the note is played, when a guitarist's pick is a nanosecond away from hitting the strings, a drummer's stick is a micron away from contact with a cymbal – these are real events that only the best components can replicate. The silent background of the Isabella also increased the dynamics of the music, especially the micro-dynamics that occur on good recordings of orchestral and jazz. The black background of the Isabella preamplifier was not its only positive characteristic. I have a feeling, though; its quiet background is one of the reasons why the Red Wine Isabella's has so many other positive characteristics.

Once again speaking of the 1970s, the recordings that conductor Andre Previn made with the London Symphony Orchestra during this era on the EMI label are some of my favorites. This isn't only because these are great performances of some great works, but the sound quality of those UK pressings are some of the best that were available at that time, and were still plentiful and not too expensive for a long time after that. I assembled a nice sized collection of these LPs. I was thrilled when I found an LP of Prokofiev's Cinderella, but alas, by the time the 1970s drifted into the 1980s EMI had switched to a digital recording process. How does the sound quality of this LP compare to Previn's other Prokofiev works recorded earlier in his tenure as musical director of the LSO? How would you like to use a digital component from this era? This is the caliber of the gear that the engineers had to work with in those days, and the recordings reflect this. Perhaps I'm being too harsh. Now that it's been transferred to CD, at least if one does not directly compare it to most other mid-70s LP EMIs, version of Cinderella doesn't sound that bad.

When played as a FLAC file through the Benchmark DAC1USB on the system containing the Red Wine Isabella preamp I was able to enjoy this recording quite a bit. Previn's version of Cinderella can't stand up to some other conductor's versions in the catalog (I'd rather not join that debate right now), but it is pretty darn good, and if judged on sound quality alone this CD/FLAC file holds up fairly well. The string sound isn't strident or steely by any means, and even if a bit of grain still remains it is actually quite lush sounding in many sections of the score. The plethora of percussion devices that Prokofiev liked to employ in his ballet scores comes through as realistically as I've ever heard them. In fact, the entire orchestra, laid out before me, its multi-layered soundstage between and behind the speakers, is quite impressive. The Isabella's slightly warm sound smooths out just about all of the digital nasties that still remain on the recording, and I was able to enjoy the recording for what it is – a very passionate reading of a score that even though is overshadowed by Previn's own Romeo And Juliet, can still hold up as both an ballet score that is played rather regularly and occasionally performed concert suite. And enjoy it through the Isabella I did – I listened to just about the entire score in one sitting because I got lost in the piece, judging not the recording quality or its sound quality but just great music making. The Isabella was able to draw me in through its musicality, and that is just about the highest praise I can give a piece of audio equipment.

Summing It Up
The Red Wine Isabella Renaissance Edition preamplifier is a fine piece of audio equipment that is available at a very reasonable price. It has three gold-plated unbalanced RCA inputs and unbalanced RCA jacks for output. If these features fit your system, then I think you've found a perfect candidate for inclusion into your hi-fi. If one has doubts that a vacuum tube preamplifier can compete with the sound of a modern solid-state preamp I think one might need to sit down and hear what tube preamps are sonically capable of these days. And better yet, a tube preamplifier that is battery powered! Yes, the Isabella has a slightly warm demeanor, but this is hardly its dominant trait and tube rolling can ‘customize' the sound to your system's liking. It has so much more to offer it seems almost unfair to its competitors. An audition is not only recommended but absolutely necessary.

Specifications
Type: Battery Powered vacuum tube stereo integrated amplifier with USB DAC
Tubes As Supplied: Two 6H30 "Super Tube"
Accepted Tubes:
     6H30, 6922/E88CC, 6DJ8/ECC88, 7308/E188CC
     7DJ8/PCC88, 6N23, 6H23, 6N11, and 6GM8
Frequency Response: 10 Hz to 120 kHz (+/- 0.5dB)
Input Impedance: 100 kOhm
Output Impedance: Less than 1 kOhms
Gain: 0dB /12dB (selectable)
Power supply transformer/rectifiers in signal path: none
Battery: Red Wine Audio 25.6V LiFePO4 battery pack
Battery Charger: 30V, 2A LiFePO4 battery charger, input voltage range 100 – 240 V 30/60Hz
Battery Duration: 6 hours with optional Isabellina DAC and 8 without Isabellina DAC
Dimensions: 13.5" x 10.5" x 3.75" (WxDxH)
Weight: 10 lbs. without charger
Price: $3995 (as tested)

Company Information
Red Wine Audio
800 Main Street
Suite 125
Holden, MA 01520

Phone: (774) 234-0800
Email: vinnie@redwineaudio.com 
Website: www.RedWineAudio.com