Product Review

Manley 300B Stereo Tube Preamplifier

June, 2004

Jason Victor Serinus


Click on the photo above to see a larger version.



● Gain: 18 dB
● Internal Variable Feedback: 8 to 12 dB Adjustable
● Noise Floor: -70 dB (1 Hz - 100 kHz)
● S/N Ratio: 105 dB (A WCT, 20 Hz - 20 kHz)
● MFR: 5 Hz - 50 KHz ± 1 dB
● THD+N: -80 dB
● Input Impedance: 100 kOhm
● Output Impedance (Line Stage): 100 Ohms
● Output Power (100 Ohm Headphones): 1W (10 V RMS)
    (28 V P-P)
● Power Consumption: 170 Watts (1.4 A @ 120VAC)
● Dimensions: 3.5" H x 19" W x 13" D
● Weight: 28 Pounds
● MSRP: $5,250 USA

Manley Laboratories



I have often wished to review Manley products. Part of the fascination comes with EveAnna Manley herself. A powerhouse of a woman who seems to pride herself on holding more than her own with the guys, the idiosyncratic EveAnna, complete with colorful headgear and a husky voice you can hear across the room, is a show unto herself. No navy blue suit-clad businesswoman here.

Needless to say, EveAnna is one smart cookie. She may not design the equipment, but she has a lot to do with its success in the marketplace. Read the website's FAQ page to get a sense of how on-the-mark this off-the-wall woman can be.

In a curious way, Manley home audio equipment (not the major aspect of the company's business) has the look of EveAnna herself (or is it the other way around?) Taking its name and running with it, the gear consistently proclaims MANLEY in letters large enough to read from anywhere in the room. Even your next-door neighbor peering into your windows will know what brand of equipment you own, and in this case, they will be impressed.

Manley gear in general has a rugged, down and dirty, masculine look about it, which is very appealing. The tubes may be curved and fragile, but the gear looks to be built like a fortress. This is Manley stuff, it seems to say.

Curiously, given its rugged exterior, I've often found the equipment quite sweet in sound. Underneath that cold, ice and metal exterior lies a most sensitive heart.

Intrigued by its aura of manly intrigue and feminine warmth, I immediately bit on our Editor's offer to review the yin and the yang of the Manley 300B preamp.


The equipment arrived without a manual. My first check of the Manley website, whose design and layout are as wild as EveAnna herself, did not succeed in locating one. At least some of company's other preamp pages had links to manuals, but the 300B's did not. It was only when I clicked on the home page's “Tech Support” link that I discovered a link to PDFs of manuals for all Manley products.

The 300B preamp has been in production, with modifications, since 1996. Designed by David Manley, it utilizes a pair of 300Bs triodes which are complemented by two 6SL7GT plus two 5AR4s and two 0D3s to create a preamp powerful enough to drive either two amps or two headphones.

The preamp uses a 24-position gold contact Grayhill attenuator switch with metal-film 1% 1/2 watt resistors and a widely separated ceramic switch for input selection. In its most-used central positions, the attenuator adjusts volume in 2 dB increments. (When I have encountered attenuators that adjust in 3 dB increments, I've often been frustrated to discover that the volume I want lies somewhere in between settings.) Gold plated connectors, high purity copper wire, Mil-spec printed circuit boards with extra thick copper and plating, and custom designed transformers are also employed.

The 300B has two sets of identical RCA main outputs to use when bi-amping. All five inputs use unbalanced RCA jacks. The REC OUT output is not buffered and thus is only recommended for recording purposes. When one is not recording, it is wise to disconnect cables from this output because the preamp lacks a buffer amp to isolate the effects of loading and cable capacitance.

The front panel sports two 1/4” headphone plugs, both of which are transformer coupled. Selecting headphone operation mutes line outputs.

Headphone output impedance can be set to either 30-400 ohms or 300-4000 ohms to best match the headphones. The difference in impedance is achieved by using the two transformer output windings in either series or parallel. Choosing the wrong headphone impedance will result in a slight attenuation on extreme highs.

The front panel's input switch allows a choice of five inputs: Video (audio), CD, Tape, Tuner, and Aux. All except tape are interchangeable.

A 30 second wait is recommended between turning on the preamp (first) and turning on your power amp (last). While one can listen immediately, 30 minutes are required for maximum warm-up. It is neither necessary nor recommended to leave the preamp on all the time.

Setup is a simple as inserting the tubes that are packaged separately, being sure to insert the square peg into the round hole. If you don't force it, the way will become clear. Because the Sovtek 300Bs supplied with the unit are very tall, I took the opportunity to readjust the height of my rack's shelving. This included leveling my transport by opening the tray, inserting a CD, and then making sure it was level. A good hour later, I felt I had benefited from the experience.

Curiously, sometime after Manley created its online manual, it added a third switch to the top of the preamp. In addition to the headphone/line output and a headphone impedance switch, one can set the line output to either Transformer or Direct. The Direct setting bypasses the output transformer, which otherwise would prevent any DC from getting to the power amplifier input. Once assured that this would not present a problem with my tubed Jadis Defy 7 amp, I listened in both modes. As you will read below, there is a significant difference between them. Note that the Transformer mode is primarily for use with headphones.

Click on the photo above to see a larger version.


Because I've been spending the bulk of my time listening to the Theta Generation VIII DAC/preamp, adding the Manley to the mix necessitated connecting my spare set of Nordost Valhalla RCA-terminated interconnects and Elrod EPS Signature 2 power cable. After cleaning every connection, powering up the units for several hours, and playing the Ayre demagnetizing and break-in tones, I engaged in my first round of critical listening.

My initial setting was in the Transformer mode. The first disc I listened to was one I had just reviewed (see this issue's CD reviews), tenor Rolando Villazón's disc of Italian arias. I was immediately impressed with the unit's beauty of sound and great dynamic range. “Wow” was my initial reaction.

Then critical mode kicked in. Perhaps the highs are a little less extended, thought I, but the sound is still gorgeous. Is the orchestral sound as full? Is the voice a little fatter and more spread in the middle, with less of a defined edge on top? Is there more echo on the voice? And regardless of all that, am I still finding myself seduced?

Although the six discs I listened to that session continued reveal aspects of the preamp's fundamental sonic signature, the experience mainly served as a reminder that interconnects and power cables take awhile to settle in. A day later, I was listening to a much superior preamp. It's the extended period I spent with the preamp after the settling in period that you'll be reading about.

I began by listening to the wonderful Chesky disc of Rosa Passos, Ron Carter and friends. On my Theta, the sound was very direct. The marimbas sounded very far back in the soundstage, separated from other instruments by absolutely silent, transparent space. I also noted the focus and pitch of Carter's bass, and the amount of echo and air around Passos' voice.

Then I listened via the Manley set to Transformer mode. I found Passos' voice a little softer, as were the instruments. There was less of a defining edge, less of a sense that the instruments were spread out across a wide and deep soundstage. Plucks on the guitar's strings, for example, had less of a percussive impact. Everything I heard seemed a bit sweeter in color and more homogenized. Wire brushes on cymbals didn't stand out as much. In place of all that, I heard even more “air” and echo. But I did not sense that this air was necessarily inherent to the recording itself. The sound was unquestionably beautiful and in no way offensive. But when I sought crisp detail, I could not find it.

In this sense, listening via the Manley in output transformer mode was analogous to real-life listening. If you sit very close to musicians, you will hear great detail. Highs, which lose edge and brilliance as they travel through space, seem very clear and present. They may even seem too bright, making you want to move back a bit.

Move back in the hall, and everything sounds mellower. Beyond a certain distance, instruments and voices begin to blend, as details fade into the overall sonic landscape. Highs sound mellower and softer, while the bass remains virtually the same in impact. (This is why you hear the bass from your neighbor's sound system, but not the violins.) On the other hand, there is an overall glow and reverberation (some call this air) surrounding the entire musical gestalt that you quite possibly did not hear up close.

It was now time to listen in Direct mode. In discussion with my audio guru friend David Tonelli, we deduced this meant that the output would be driven directly by the tube, without any buffering. John Johnson told me to be sure to turn off the amp first, then the preamp, before switching between modes. I did that for awhile, being sure to turn the preamp on first, wait 30 seconds, and then turn on the amp. No problem.

Eventually I followed David Tonelli's suggestion that turning the preamp off before switching was unnecessary.

With my equipment, I found David's advice correct. John's admonition is of course applicable in cases of shorts, but everything I was using was working fine. I heard neither pop nor change in volume level as I switched between settings. But I did hear major differences.

In “Direct,” I heard more of the vocal breathiness Passos intentionally employs. Strums on the guitar stood out more. Detail was unquestionably greater. What was still missing, compared to listening only to the Theta, was the sense of absolutely silent space between instruments and voice. I also noted that while the brushes were certainly crisper in impact, they were still slightly soft.

Once you grasp a unit's sonic gestalt, further listening may simply tend to reveal greater nuances rather than change one's impression. Such was the case when I played Reference Recordings' superbly recorded Rachmaninoff Symphonic Dances.

On Direct, the setting where I left the preamp after my journey through bossa nova land, the entire orchestra's sound seemed a little softer. A telling example was the horns, which had less of that sit-up-and-listen brass glare to them. The plucks on the double bass as well seemed softer in impact, and the triangle's sound was a bit less shimmering and free. With Transformer engaged, overall impact was softer still, and equally sweeter. Drums had less thwack, edges of sounds blended together. The orchestra seemed a little wimpy, as though conductor Oue had failed to whip them into shape.

From Russia to Germany. Hilary Hahn's Brahms followed suit. Direct, to me, seemed the more preferable setting (albeit perhaps potentially electronically riskier), because it provided more detail, a less homogenized sound, and more variation in color between instruments. Yet when Hahn's violin entered after the long orchestral introduction, I found it still had less distinction in color from the strings accompanying it than I was used to hearing.

Returning to the Theta, I was again reminded that Hahn's violin is notable for its big, multi-layered sound. The Theta conveyed far more complexity to the instrument's tone, with more of a glint to the upper strings. Indeed, it is this glint, emerging as it does on highs in the same way that Elisabeth Schwarzkopf's voice first bowled me over in her famed early commercial recording of Bach's astounding cantata for soprano, "Jauchtzet Gott In Allen Landen BWV. 51", that adds to the specialness of Hahn's performance. Even in the Manley's Direct mode, this glint was not as pronounced as through the $10,000 state-of-the-art Theta.

While the Manley was in the loop, I welcomed my sister-in-law and brother-in-law to our new home. I had a gift for Kathleen, EJ Mills Brennan's beautiful independently produced CD, Breath of Prayers III. I had last heard this disc before the Jadis Defy 7 amp changed my life.

We were all struck by the beauty and sincerity of EJ's grounded voice, simply accompanied by piano and flute. Even the instrumental compositions seemed etheric in impact.

Yet as much as everyone loved what they heard with the Manley in Transformer mode, they all immediately noted the difference when I bypassed the Manley and instead used the Theta as both DAC and preamp.

Although everyone wanted to play immediate critic, ignoring the music, I urged them to continue listening before proclaiming final judgment. When the proverbial gong was sounded, “muted” was how David described the sound of the disc through the Manley's output transformer. I prefer to say homogenized rather than muted, but I think this second person perspective will help you further understand the Manley's unique sonic signature.

Is this a result of the 300B tube? When I asked David Tonelli, he replied that he had never heard two 300B units sound alike. Perhaps the Manley would sound different if one tried General Electrics or other brand 300Bs. But with the stock Sovtek tubes, I believe I've done an accurate job reporting its sound.

I also wish to note that I spent considerable listening to a host of other recordings with this preamp, including Abyssinia Infinite's gorgeous and rousing Zion Roots that includes the remarkable vocal soloist “Gigi” Shibabaw, chorus, saxophone, and drumming. My impressions remained consistent regardless of music played.

As a Headphone Amplifier

A main rationale for the 300B is its dual function as a headphone amp. Unfortunately, there is a lack of decent headphones at Casa Serinus. My elderly pair of AKG 240s with a loose left channel will not do for review purposes.

The situation was soon remedied by an emergency call for help to fellow members of the Bay Area Audiophile Society. My sincere thanks to Mike Zumbrunnen and Jeff Wilson for their gracious loans of Sennheiser HD 600 and Grado RS-1 headphones, as well as battery-powered Headphone and Grado headphone amps.

In preparing to audition the dual headphone feature of the 300B preamp, we contacted EveAnna to check on correct preamp settings for headphone listening. It was only then that we learned that the 300B preamp should be played in direct mode when listening through speakers and output transformer mode when listening through headphones. Ah, if only it had either said so on the preamp itself or in the online manual that EveAnna is now poised to update.

One cool thing about the 300B's dual headphone option is that it allows two people to listen simultaneously. Of course, this is only practical if both sets of headphones require identical volume settings and the two listeners have relatively equal hearing ability. Assuming those two conditions are met, partners can inhabit individual worlds, yet hold hands while listening in silence. It's a bit like tripping, albeit far more contained. Which, depending upon the outcome, may need the beautiful sounds of the 300B to remedy a bad trip. Or one of you can lie in bed while the other sits at the desk paying bills.

I adjusted the impedance setting for each headphone. The Grados preferred 30-400 ohms, the Sennheisers 300-4000 ohms. The Sennheisers also required more volume. Out went the idea of reviewing by switching back and forth between the two without having to adjust volume.

I was delighted at what I heard. Taken on their own terms, good headphones plugged into the Manley deliver quite satisfying, innately musical sound.

Of the two headphones, I greatly preferred the Grados. The Sennheisers may have sounded mellower and softer on top, with more midrange emphasis, but the Grados seemed far more open, extended and accurate. The Sennheisers sounded sedate, almost muffled when compared to the Grado's aliveness.

As one might expect, neither headphone supplied the room shaking bass, vibrant highs, depth, and air heard through the Khorus X. The impact may have been quite immediate, but it touched me less on emotional and visceral terms. Regardless, taken on its own terms, the 300B/Grado Reference Series 1 headphone proved quite satisfying. Highs were alive and vibrant, bass well defined, with a decent amount of air in between and around sounds.

When I plugged my system and the headphones into the Grado headphone amp, I definitely heard the greater directness and clarity afforded by battery power. What I also heard, however, were some pretty glass-shattering cymbals and a concomitant lack of air and grace. My ears were not happy. The little Grado headphone amp simply could not touch the musicality of the Manley 300B. For headphone listeners, the Manley is a must-audition.

On the Bench (JEJ)

All measurements were performed in the Transformer setting.

THD with a 1 kHz sine wave input was slightly more than 0.1%. The distortion is mostly second order. The noise floor is about 80 dB below the fundamental frequency output level.

With 1 kHz and 1.5 kHz sine wave input signals, IMD was very low.

Using 5 kHz and 6 kHz sine wave input signals, IMD was, again, quite low.

THD was just over 0.5% with a 10 kHz sine wave input signal.

The frequency response was ± 1 dB, 20 Hz to 20 kHz.

The Qualifier

Ever since obtaining the Theta and the Jadis, my reviews have included caveats. This one is no exception.

The Theta Gen. VIII is a state-of-the-art unit. Because it combines DAC and preamp in a single unit, it shares characteristics of a one-piece CD player that also boasts a volume-controlled output. There are less stages, fewer interconnects, less in the signal path that might modify or alter the signal. It is only to be expected that the Theta will sound more transparent and direct when auditioned by itself than with anything but a top-of-the-line separate preamp in the chain.

Note that I have not found the Theta “digital sounding” in the least. I experience none of the harsh glare, etched quality, flatness, or transistorized sound commonly associated with digital reproduction. Mated with the tubed Jadis amp, the Theta does not require the extra warmth or sweetness of a tube preamp to make it sound more musical. The match is heavenly as it is.

I will be listening to Manley 300B further when comparing it to the next preamp next on my review schedule. If I can keep the Manley long enough, I'll also compare it with preamps from additional manufacturers. Please refer to those reviews for an even more complete assessment of the Manley 300B. Meanwhile, I share with you my preliminary conclusions about the Manley in the current review.


I have greatly enjoyed my time with the Manley 300B preamp. I found it among the most musical preamps I have had the pleasure of auditioning chez Serinus. In fact, I want to listen to it some more.

The Manley's sound, a bit sweet, just a bit soft, offers a slightly euphonic presentation with lots of tube-like air. Its presentation is very much alive, with most of the sparkling highs I hear from the extraordinary Theta plus an extra degree of warmth and air.

Harking back to the Audio Note M3 preamp I reviewed some months back. I recall that it provided far “more of the same” than the Manley. Between the two, the Manley definitely gets my vote. If neutrality, transparency, and directness are the ideal, the Manley 300B seems far closer to that ideal than the Audio Note M3.

The Manley also gets my vote as a strong candidate for pairing with solid-state electronics. It sounds great with the Soaring Audio amplifier, and I'm sure would sound great with a host of other solid-state amplification. Precisely the sweetness, forgiving presentation, surfeit of air, and digital glare balancing warmth many of us desire from a tube preamp are here for the asking. Many solid-state products have pronounced highs and bass, yet lack midrange warmth. The Manley should provide a near-ideal complement to a system with such components.

The 300B is most definitely deserving of audition if you're shopping for a tube preamp. It's an absolute necessity if headphone listening contributes greatly to your aural satisfaction.

- Jason Victor Serinus -

Associated Equipment:

Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII

Perpetual Technologies P-1A with modified Monolithic Power Supply and Revelation Audio umbilical power cable (not used for this review)

Jadis Defy 7 Mk IV modified with a Siltech silver harness

Bruce Moore Companion III tube preamp with Electro-Harmonix gold pin 6922s and Jan Philips 12AU7 equivalents;
Reflection Audio OM-1 Quantum battery-powered preamp in non-battery mode (used for this review)

Talon Khorus X speakers (with latest modifications and Bybee filters that render its response even across the spectrum and greatly improve the bass)

Nordost Valhalla interconnects and digital interconnects
Nordost Valhalla bi-wired speaker cable
Powercables: Elrod EPS-1, 2, and 3 and EPS-2 and -3 Signature on main chain plus Harmonic Tech, Nordost, and AudioPrism SuperNatural S2 elsewhere

PS Audio P600 Power Plant power synthesizer with MultiWave II
PS Audio Ultimate Outlet; PS Audio Power Ports
Michael Green Deluxe Ultrarack, Basic Racks, room treatment, and Audiopoints
Ganymede supports under amp and transport
Black Diamond Racing Cones
Shakti stones on Amp, Monolithic/P-1A and Theta
Bedini Quadra Beam Ultraclarifier
Audioprism Stoplight and latest, Marigo Stealth Mat for CDs
Sheffield/XLO degmagnetiser and break-in disc and Ayre demagnetizing disc

© Copyright 2004 Secrets of Home Theater & High Fidelity

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