November 2024

Manley Labs Oasis Vacuum Tube MM / MC Phono Stage Review
Manley Labs vacuum tube Oasis phono stage produces excellent sound quality.
Review By Tom Lyle

   My first experience with a Manley component was in the late 1990s. I was working at a well-known recording studio mastering an album when the chief engineer insisted we use their vacuum tube-powered Manley Stereo Variable Mu Limiter-Compressor, which I had no idea at the time was one of Manley's first products which was introduced in 1994. We had the music signal pass through the Manley compressor but kept all its settings on default. This happened quite a long time ago, so I can't recall any specifics about how the Manley affected the album's sound quality other than passing the signal through this studio component made the album sound closer to our goal of making it "sound like a record."

Shortly after, I learned that Manley designed and manufactured high-end home-system audio products. I've wanted to review one of their products since then, and I'm finally having my chance!

The Manley Oasis is the successor to their Chinook phono stage, yet the Oasis isn't much more expensive. Still, the Oasis' $4,000 price tag might be out of reach for many, especially for younger audiophiles. But even if it shares only a few traits with Manley's top-of-the-line Steelhead phono preamp, this should be enough to consider it worth saving for.

This spoiler shouldn't be that much of a surprise for anyone familiar with the Manley imprint. Plus, the Oasis phono preamp is much more than simply an upgraded Chinook, and in this review I'll explain why.

The Manley Steelhead Versus Oasis
For quite a long time, to those who could afford it I recommended Manley's top phono preamplifier, their $10,900 Steelhead, introduced in 2001. The Steelhead has front panel loading settings as opposed to the $3,999 Oasis' rear panel DIP switches, it has three inputs as opposed to Oasis' single input, has a remote control option, among other superior features, and is, of course, reference quality.

Although the Steelhead is superior to the Manley Oasis in many ways, the Oasis is hand-crafted in the same factory as the Steelhead, located in Chino, California, about 35 miles from Los Angeles. However, as the Steelhead is superior to the Oasis, the Oasis is superior to its predecessor, the Manley Chinook phono stage. The improved power supply was the most significant factor in improving the Oasis' sound quality over the Chinook, but this wasn't its only upgrade.

Also improved was the Oasis' user-friendliness. The Chinook's gain settings were internal, forcing the user to remove this phono stage's cabinet to make any changes. The Oasis' gain settings are alongside its resistive and capacitive loading DIP switches on its rear panel, making its initial setting much more accessible. Those who need to make changes will find it easy to make any modifications. The Oasis's resistive and capacitive loading options allow practically any moving coil (MC) or moving magnet (MM) to be used.

The Oasis also boasts an upgraded chassis design. However, its more efficient internal design keeps it in its relatively affordable price range. Continuing its surprising similarities to Manley's Steelhead, each channel of the Oasis uses two triode sections of a 6922 vacuum tube to boost the signal of one's phono cartridge. It is aided by low-noise FETs located below each cathode. It should shock no one that the Oasis employs "highly accurate" passive RIAA networks.

Details
The audio signal doesn't pass through any integrated circuits (ICs) in the Oasis. ICs apply a precise biasing voltage to the FETs, and some chips perform LOGIC functions to direct the turn-on and off sequences. These sequences use mute relays to prevent noise when this phono stage is warming up after being turned on from standby. The front panel on/off switch is lit when the Oasis is connected to the AC. This switch will blink for a minute or so after it is pressed while the Oasis warms up, then is solidly lit when ready to play music.

On the Manley Laboratories, Inc. website, they stress the significance of their coupling the signal directly from the gain stages to a 6922 dual triode vacuum tube, which serves as the output driver in a "White Follower" configuration (this patented method is similar to a single-ended design, but different). This output stage circuit, says Manley, is their favorite because of its inherently low output impedance and "beefy current-driving capabilities". This allows it to drive very long cables and difficult loads. On Manley's website, they describe the results of this method as enabling them not to use any "wimpy cathode followers."

Playing Records
I was fortunate. I was one of the few who kept all their vinyl in the 1990s through early 2000s, what I term the "CD era." Sure, I purchased many CDs, but also as much vinyl as I could find, such as the meticulously pressed analog-mastered Led Zeppelin catalog pressed by Classic Records. And so, one of the first albums I played during the Oasis' review period was the incredible-sounding Led Zeppelin III. Its mix of genres makes for a perfect demo disc. It has everything from quintessential hard-rock, like the Nordic-inspired "Immigrant Song, and hard rockers such as "Celebration Day." There are also plenty of acoustic numbers, including "Friends" and "Tangerine." Yet, in some of these ballads that feature drummer John Bonham, their trademark heaviness comes through. In my humble opinion, it is one of the greatest albums considered "Classic Rock" by those younger than I am.

A Dynamic Performer
My analogy front-end for this review consisted of a Basis Audio Model V turntable and a Top Wing Suzaku "Red Sparrow" phono cartridge mounted on a Tri-Panar 6 tonearm. With this turntable setup, I could easily hear what the Oasis was sonically capable of. When spinning this Led Zeppelin vinyl LP, I could sense the sound pressure levels surrounding my reference Sound Lab Majestic 545 electrostatic speakers, aided by a pair of SVS SB16-Ultra subwoofers. Not only did this breathtaking sound surround the speakers, with a soundstage that extended beyond the front wall of my listening room, but it also engulfed me.

I love the qualities that good tube-powered components impart to my system, regardless of where they might be in the audio chain. The Manley Oasis possessed a good tube component's most marvelous trait: the ability to impart a dynamic distance between instruments.

Dynamic distance is the ability of an audio element to not only separate vocals and instruments from each other but also to separate sounds that occupy the same space on the soundstage, even when they are playing at the same volume. This attribute was easy to hear on "Gallow's Pole," Led Zeppelin's take on Leadbelly's classic from the 1930s, which he adapted from the centuries-old folk song about a condemned woman's pleas to the onlookers to buy her freedom from the hangman's noose. This song has layers of different instruments and voices recorded onto the multi-track tape.

The crowded soundstage coming through my speakers included Robert Plant's multi-tracked vocals, Jimmy Page's electric guitar, acoustic six and 12-string guitars and banjo, John Paul Jones's mandolin and bass, and John Bonham's drum kit. I was amazed how the Oasis was not only able to separate each of these instruments and vocals in the soundstage, so much so that it was as if I could "see" behind each instrument and voice.

The Manley Oasis communicated all that I love about this album. Even though the Oasis had a bit more background noise than my reference Pass Laboratories XP-27, on this album the noise was only present when no music was coming through the speakers. It is good to remember that my reference Pass Labs phono preamp is a solid-state component that costs about three times as much as the Oasis.

Vacuum Tube Rolling
Still, background noise was there, and when listening to music with passages that might be very low in volume, such as when I played my new copy of Jackie McLean's It's Time, one of Blue Note Records incredible "Tone Poet" reissues mastered by Kevin Gray. On this album the background noise was sometimes a tad intrusive. Since I wasn't anywhere near the first reviewer who had the pleasure of reviewing this sample of the Manley Oasis stereo MM/MC phono stage, I thought that perhaps the repeated handling by various shipping companies might have had some adverse effect on the tubes, so I switched out the input tubes for a matched pair of Amperex 6922 tubes that I had.

These tubes didn't change the basic character of the Oasis' sound quality very much, except now the background noise was nonexistent. This aided in all the sonic qualities that one would expect from having a silent background.

I chatted with EveAnna Manley and asked her opinion about switching out the tubes, and I was relieved when she said, "It seems as if your Pass Labs XP-17 MM/MC phono stage operates about 10dB quieter than the Manley Oasis as per its specs, but as you discovered, the noise level of the Oasis is reliant on selecting quiet tubes, and I am happy that you had a stash of quieter tubes to roll into the gain stage to knock the hiss down a bit!"

Lastly, Its Exterior!
I'm not usually that concerned with the appearance of a component's appearance. Its performance has always been my first concern. But Manley components are an exception, as I've always been impressed with their cabinet design. The exterior of the Manley Oasis is worth mentioning. It has a chic-industrial design similar to Manley's other good-looking components. The Oasis's chassis is powder-coated over a non-reactive steel design. It has a 3/8" CNC milled faceplate with a laser-engraved "Manley Oasis" logo. The Oasis is available in its traditional "Manley Blue" but also in silver or black.

In Conclusion
I can imagine some audiophiles purchasing a Manley component sight unseen. As I hinted at in this review, Manley's reputation precedes itself. And so I wouldn't reprimand any audiophile simply buying a Manley Oasis without reading any reviews. Thankfully, some do read the reviews! I hope I've made it clear to those audiophiles that I highly recommend the Manley Oasis phono preamplifier without reservation. Yes, it might be financially out of reach for some audiophiles. For those who can afford it, I say go for it.

One of the definitions of the word oasis is: "Something that provides refuge, relief, or pleasant contrast from what is usual." Manley Laboratories, Inc. couldn't have chosen a better moniker for the phono preamplifier.

Specifications
Type: Vacuum tube stereo MM / MC phono stage

Vacuum Tube Complement: Two 6922 (gain stage) plus two 6922 (output stage).

Input And Output: Manley Labs Teflon and gold-plated RCA jacks.

Automatic Mute Timer: On initial power up output jacks are muted for approximately 45 seconds. 

Input Termination Capacitance: Three-position user-selectable capacitor values of 50pF, 100pF, and 200pF yield resultant combinations of: 50, 100, 150, 200, 250, 300, and 350pF.

Default Input Impedance: 47k Ohms, with no other DIP switches selected.

Selectable Input Impedance: Five-position user-selectable resistor values of 50, 100, 200, 400, and 800 Ohms.

Custom Cartridge Input Load Impedance: User may solder a fixed resistor value.

Dimensions: 17" x 14" x 3.5 (WxLxH)

Price: $3,999

Company Information
Manley Laboratories, Inc.
13880 Magnolia Ave.
Chino, CA 91710

E-mail: sales@manleylabs.com
Website: www.Manley.com