I was able to convince Vinnie Rossi from RedWineAudio to send me his Isabella headphone amp/preamp for review. The Isabella is a high end product to be sure, and the physical design is luxurious – beautiful casework, nice touches like a touch-sensitive power switch, high-end chassis-mounted jacks, etc,., etc. – it is incredibly well built and is a thing of beauty to behold:
Really the only nit I can pick with the construction is the rear-panel location of the headphone jack. This could be major pain for some folks, depending on their intended usage. According to RWA, this is done to provide the shortest signal path. And it does also show that the real intent of this product is as a high-end stereo preamplifier and DAC, more than as a stand-alone headphone amp for its own sake (although the headphone amp is truly world-class in its own right). So does its price – at $6,000, it costs more than any single piece of hi-fi gear I own except for my main loudspeakers.
One of the Isabella’s main features is its power supply. The Isabella uses an integral battery power supply that is charged with a supplied AC charger. The amp can run off AC or battery at the flip of a switch. This also allows instant comparison of the sound in either mode. No doubt the battery supply improves the sound – backgrounds are blacker, and noise is subtly but audibly reduced. If you want to do battery power supply, this is the best way to do it – battery power, but with the built in charger. I hate the idea of using actual disposable batteries to power an audio device, and the Isabella does not require this. The battery supple is very well implemented. My only complaint here is again my preference would be to have the AC/Battery switch on the front rather than on the back. But as for sonics – this is a terrific feature.
The Isabella uses 2 6DJ8/ECC88/6922 type tubes. They are housed under a glass door for easy access – another nice touch. The amp was supplied with JJ tubes, and while I did listen to them, I fairly quickly subbed in NOS JAN-Sylvania short gray plate tubes which sounded MUCH better than the JJ’s. Vinnie agrees that NOS tubes sound better, but it is basically impossible to provide the amp with NOS tubes in it. But if you are able to spend $6K on a wonderful amp like this, don’t hamstring it with mediocre tubes. Spend the money for some nice NOS tubes. It will be well worth it.
The DAC in the Isabella is superb as well. It sounded better than my Denon CD player and my higher-end Denon Universal Player. I don’t own any stand alone DACs with which I could directly compare it, but the Isabella has a lot of flexibility by having an internal DAC of very high quality. I also listened to the Isabella via USB being fed Apple Lossless files from my PC. Here again the sound was excellent, however, I find ALL USB DACs to have a slightly grainy quality compared to being fed a coaxial input from a CD player, and the Isabella was no exception. The COAX input provided better sound than the USB input IMO. It was also quieter with no music playing.
I used the Isabella both as a headphone amp and as my main stereo preamp, where I listened to Vinyl via my B&W Nautilus 800 Signatures and Sunfire 600 Signature power amp. My thoughts on the sonics as outlined below apply equally to both modes unless otherwise indicated. I used mostly the Beyerdynamic DT990/600 and the JVC DX1000 for the review.
Let’s get the gushing out of the way. The Isabella is the best sounding headphone amp AND the best sounding preamp I have ever had the privilege of having in my home. It was better than any of my Singlepower amps, better than my Krell preamp, and sounded better as a DAC than my Denon DVD-5900, and took my main hi-fi to another level. I desperately wish that I could afford to buy it. It sounds phenomenal.
And in a way, this is because it doesn’t actually sound like anything. This review will differ significantly from my other reviews in this regard. I normally write a review that essentially describes the sonic flavor that the product in question imparts on the sound. But the Isabella is in another league here. I’m not sure I had even experienced true neutrality or transparency before. While my Krell preamp comes very, very close, the Isabella is at once more colorless and also more musical. Some of what I perceive from the Krell as neutrality is actually some “enhanced” etch and detail that the Isabella doesn’t burden the listener with. The Isabella has all the detail of the Krell, but delivers a more relaxed musical presentation without using sonic colorations to deliver it. It was breathtaking.
Listening to the acoustic version of Porcupine Tree’s “Lazarus” on LP, I had major league goose bumps. When the backup vocalist joins Steve Wilson, it was just positively spooky. In fact, it was so transcendent an experience that I get goose bumps just thinking about it! It was really amazing. Listening to “Dark Star” from “Live/Dead” by the Grateful Dead, I could hear texture in some of the percussion that I wasn’t aware was on that recording, and I have heard this record many, many times.
I had always considered my Singlepower Extreme to be a highly transparent amp. And in the grand scheme of things, it is. But it is not in the same league as the Isabella in this regard. The Isabella sets a new reference point for me in terms of what transparency means in an audio device. I am quite certain it’s the most transparent sounding audio device I have ever heard.
Let me try to illustrate this point. When listening to King Crimson’s excellently recorded “Absent Lovers – Live in Montreal 1984”, there is a degree to which the Isabella allows you to really feel like you are actually in the hall that the SP Extreme, as good as it is, just does not quite manage. Also, when listening to Mae Moore’s “Love Will Bring You Back” from “It’s a Funny World”, there was a slight grain to the vocal on the Extreme that was missing on the Isabella, making the vocal presentation that much more liquid. When listening to the Extreme on its own, it does not seem to have any shortcomings in this regard, and I believed that it was all the headphone amp I could ever want. But now having heard the Isabella, I know that there is another level. Such is the danger, I suppose, of reviewing equipment that you cannot really afford
The Isabella does all the sonic checklist things right, when called for by the music. Subterranean bass? Listen to “It Doesn’t Matter” from Alison Krauss’s “So Long, So Wrong”, and yeah – all the crazy deep bass you ever need is there, tight as a fist, and with as much punch as one as well. Palpable, gorgeous, luscious midrange? Yup, and again without coloration. Listening to Fiona Apple’s “The Way Things Are” truly made her seem like she was in the room with me, and having seen her live in a small venue, I knew she sounded right via the Isabella. Open, extended treble? Check. The small nuances in the complex instrumentation in Steely Dan’s “Aja” were very cleanly and clearly rendered. Soundstage? It was as it should be on the recording. Listening to “Morning Dew” from the Grateful Dead’s Live at the Cow Palace, the band was represented exactly as they should be, and sounded appropriately big. And it was just holographic. This was the one area I felt that the tubes in it were having an obvious and positive effect.
The Isabella does have tubes. But it doesn’t “sound” like a tube amp, in the sense of any of the stereotypical colorations. It really does not have a “sound”. This may be its biggest strength – just an incredible degree of transparency and neutrality, without sounding even the least bit cold or threadbare. Music just flows out of the Isabella, and one is not cognizant of it being “warm” or “cold” or “bright” or “laid back” – one is just wonderfully aware that one is listening to MUSIC. I can’t give the Isabella any higher praise than that. To a degree that I have not experienced, the Isabella lets you directly connect with the music. When Isabella leaves me, I will miss her because of this.
And leave me she will. Why? Because, sadly, I can’t afford a $6,000 preamp at the moment. I sure wish I could. I would rather have the Isabella than my car, but I have to have my car. Too bad about that. The Isabella would give me a lot more pleasure than that old Jeep does. But such is the realm of high-end audio – sound this good comes at a steep price. Give the level of construction, features, and performance, I think the Isabella is absolutely worth the investment, if you can make that investment. For me, all I can do is dream about her…pleasant dreams to be sure
REVIEW: RedWineAudio Isabella tube Preamp/DAC/Headphone amp
