POSITIVE FEEDBACK ONLINE - ISSUE 25
as reviewed by Lester J. Mertz
The Manley Laboratories of Chino, California has been introducing new and upgraded products over the past seven or eight years with some remarkably unusual names for audio gear. The first product I heard with a "fishy" name was their Stingray integrated; it was in 1998 at Arizona Tube Audio, located in Tempe, AZ. I had gone there to listen to something called the Tiny Triode amplifier, sold under the VTL (Vacuum Tube Logic) brand name. The owner said he no longer carried that brand but showed me the Stringray which he said had a similar sound, and it sounded pretty good as I remember. I mention all of this because of the connection between those two amplifiers.
David Manley worked with his son Luke at the VTL factory in Chino producing various all tube equipment and amplifiers aimed mainly for recording studio markets. The early ‘90's Tiny Triode design used the EL-84 (6BQ5) nine pin miniature pentode in multiple pairs connected in the triode mode as the output tubes for about 20 watts.
In 1993 father and son decided to go their own ways, and thus two separate companies were formed: Luke carried on with VTL while David created a new company called Manley Labs, also located in Chino, CA. However, David left Manley Labs ten years ago in 1996. EveAnna Manley bought the company from David as part of their divorce agreement. (Please check the Manley Labs website for more information on the company: www.manleylabs.com.) Both companies produced amplifiers with the EL-84, something I don't think anyone else was using at the time. Note: the EL-84 had been used many years earlier in tube integrated amplifiers and receivers. VTL, under Luke Manley, continued with the Tiny Triode, and later produced limited edition version of the amplifier, while Manley Labs continued with the ultra-linear (UL) EL-84 amplifier version that produced about 35 watts, with later upgraded versions that claimed 50 watts
It is this basic circuit that EveAnna and her brilliant crew eventually evolved into the Stringray integrated, and most recently into the Mahi mono-block design. Both Manley amplifiers share the companies' custom-made transformers and all of the recent circuit improvements like variable feedback by switch settings, just like the expensive tube amplifiers. The Mahi also has the triode/ultra-linear options, but you must power down to make that change. All of these options make for a versatile package, with both triode and ultra-linear modes each with three different feedback options.
The Mahi is sold in pairs, hence the name Mahi - Mahi, and they each come boxed separately. I received the review pair from somewhere in the Midwest, and upon opening it appeared that one of the amplifiers may have been banged about by the friendly over-caffeinated guys wearing shorts summer and winter. The Mahis are shipped with the tubes installed and secured by a nice custom-fitted foam block. But one of the amplifiers had all of the tubes canted and leaning back toward the transformers even with the foam in place. That shouldn't be a problem as both the web site and owner's manual mention that these amplifiers are "able to survive a drop of 23,487 feet or less." I'm not exactly sure of the nature or the testing done to make this claim. However, when I attempted to set each of the amplifiers on separate granite blocks, the impacted one would simply not sit squarely on all of its four outrigger feet. I did not panic here since I am a believer in hardwood blocks under electronic gear. I put three medium sized blocks under each amplifier and didn't think any more about it.
The small square amplifiers may look like toys to some because of their size, but they are seriously made audio products. The chassis is powder coated wrinkle black, and the transformers are painted crackle black with a high temperature engine block paint All the tube placements, switches and bias test points were beautifully silk-screened in white legible lettering. Quality RCA inputs and real WBT speaker posts exhibit a quality consciousness that is not often found at that price point, and I give Manley five stars for the presentation. I give the outright "best rating!" for an "Owner's Manual" that was more fun to read than anything I've ever seen. It should serve as a model for other manufacturers. Boy, after reading that was I ready to warm these babies up!
I played them for a couple of hours to get my first impression. They were "brightly lit" as they often say, not from the tubes being overly bright themselves, but the overall sound presentation itself. The amplifiers were voiced with an extremely open upper end, with noticeable presence on midrange, and lots of everything else above there. This was in the ultra-linear mode with standard feedback setting. Switching to the triode mode produced slightly more detail in the presence region, but the bass was even more MIA by comparison.
Anything worth doing is worth doing right. I had heard Manley gear at shows and during a fabulous factory tour given by none other than EveAnna herself—the fun-loving guru behind this innovative company. Their sound was always terrific. She made it clear that Manley goes to extremes to produce each product, and most everything is done in house. They wind their own transformers, and design and fabricate their own printed circuit boards. (Manley does not believe that point to point hand wiring results in consistent product to the customer, and I think they're right on this.) They have an in-house metal working shop, and also produce exotic recording gear such as world class microphones, equalizers, mic preamps, and so on.
Confident that the Manley gear was well designed and executed, I was not deterred by the forward sound of the Mahis. I left them on for several days, checking the bias and listening at both the owner's manual specified "200 milliamps" (mA) and at the amplifier's silk screened recommendation of "250 mA". I also tried listening at 225 mA. (Maybe this note will get the actual recommendation clarified once and for all.) I did not call or email the overworked staff, as the higher bias was only very slightly more powerful sounding. One thing that did reveal itself during these bias checks and changes was that the "impacted" amplifier was microphonic. When I touched the multi-meter leads to that amplifier the action produced a clicking in the speaker that was easily identified with the movement of the leads. Gently tapping my finger on the chassis also produced the amplified microphonic sound in that speaker. My first guess was the input tube (the 12AT7 twin triode) elements were loose or moveable inside that tube. I switched the left and right input tubes—no change. Next I switched the second tubes (the JAN 6414 twin triode) and the problem was resolved. After that swap the amps played without any hitches, pops or unusual tube noises other than a slight tube "rush" heard from each speaker. This was noticeable at closer than about 4 feet, but was nothing that interfered with the music.
But the sound still exhibited that brightly-lit presence peak, and my wife was having none of it. Every time she would pass the equipment rack, she would turn my Blue Circle 21.1 preamp down several clicks on the level attenuator. She said the "sound was too hard on me, and wasn't full", but what I think she means is there wasn't any weight to the music. Her hearing is much more acute than mine, and she notices brightness or edge immediately. Then she begins turning things down at every opportunity that I'm away from my listening chair. I knew she was right, but I had been waiting and hoping for the Mahi - Mahis to begin to bloom. I couldn't wait her out.
I began changing things: different interconnects, speaker wires and power cables. I found my old DH Labs Silver Sonic BL-1 Series II (I needed a 2 meter pair to reach the Mahis and most of my interconnect collection are 1 meter) gave the most even and balanced sound with the Mahis. (It is interesting how one brand of wire will sound wonderful with some gear, and completely over-cooked with another. Well, that what this audiophile thing is all about isn't it, finding out what works for you.)
After the changes I was getting more weight (bottom end) in the musical presentation. My wife started ignoring the volume levels and said that things "sounded better".
Because of the early-on tipped up sound spectrum, I had begun playing the more weighty sounding disks, particularly some of my favorite solo cello selections. They all sounded wonderfully revealing through the Manley Mahis. Full-range instruments like the piano still sounded a little out of balance, however, favoring the top end.
I tried different speakers: four separate pairs in all. The winner was the final pair—the older Dynaudio Aries (89dB/Watt/meter sensitivity) floor-standers which have a wonderfully warm sounding speaker that you can listen to literally forever! The Aries produced a most satisfying sound with the Mahis, and I stayed with this combination for the rest of the review.
The Mahi amps spec out with 18-27 watts in the triode mode depending on the feedback selected. Triode mode was easily my favorite sound with this amp. This may not seem like enough power to drive any real world commercial speakers, but it was just fine for me. I don't listen at any ear damaging levels. I suggest that for critical listening you sit in close to your speakers. Try a five to seven foot equilateral triangle with the speakers well out in the room; mine were close to four feet from the rear and side walls. You're probably ready to fire off an email telling me that's why I'm not getting any bass, and that I need to put the speakers in the corners. Please don't bother! My regular system sounds perfectly fine with plenty of real bass with this set up. I have been using modifications of this arrangement for the past six years, and the stereo imaging is out of this world, as it was with the Mahi - Mahi monos.
If you stop and think about it for a moment, no head banger is going to give this amp a second look; he or she will just go on in search of more power. In our audiophile world, those of us that listen at loud levels never seem to have enough power. I read somewhere that low sensitivity speakers (around 80dB/Watt/meter, or at approximately 0.1 percent efficiencies) would require about 40,000 watts to achieve full concert hall crescendo levels of plus 120dB! You math wizards will have already figured out that about 1.25kW per side is still needed to reach 104dB. Wow, that's a lot of power and something to think about. For my real world option, try listening at lower levels, or finding more efficient speakers, or better yet—do both!
Finding the right speakers for your favorite amplifier can be a daunting task, but one that must be undertaken. Low power tube amplifiers coupled with the smaller and relatively insensitive speakers popular today can be a frustrating experience. The low power amplifier will probably not be happy with high impedance swings caused by the ported enclosure and the simple crossovers of the speakers you may already own. Appreciate this before you run off and get a deal on another amplifier that may be the precursor of an entirely new system. That may be what is required to reach that synergy you're looking for, and you may find that your "deal" isn't a bargain in the long run, after you replace virtually the entire rig.
Nonetheless, if you have the right speakers and want to hear what's going on with small jazz and classical groups, these Manley Mahi monoblocks are simply amazing. The low feedback rates allow for a wealth of detail and nuance on every recording. Feedback has been used to help stabilize the amplifier circuits since the Bell Labs days, but using it eliminates some of the micro-details of the live music. There's no free lunch of course, and having no feedback means limited power bandwidth, and poor speaker damping and control. Manley has experimented to find a balance in either mode, triode or ultra-linear. I have to say that I liked the standard or "middle-way" feedback settings best.
Listening in the ultra-linear mode doubles the power, bringing it to over 40 watts and imparting a more gritty bite to the sound. For large group and orchestral music this was the way to go; it was nice to have the option. It was like having two amps in one. Ultra-linear mode has been around since it was patented by Blumlein (stereo's inventor) back in the 1930's. Both the Dynaco and Macintosh tube amplifiers of yesteryear used their special patented transformers to get their "house sound." Today most tube amplifiers work a compromise of this transformer winding feedback option to get their own special sound. The choices range between minimum distortion (43% screen grid tap) and maximum power out (20% screen tap) for the mode. Ultra-linear mode is not as powerful as a true push-pull pentode amp, but it's a great sounding choice, and EveAnna calls it "the best of both worlds." And yes, the Mahi - Mahis delivered a big sound in this mode with any of the speakers tried.
Tube worries: fear not. The carefully chosen tube complement should provide years of trouble-free life. Should you accidentally break an output tube, just call Manley Labs and give them the hand-written matching number on the next tube in the output line, and they'll mail the exact replacement. No, they won't force you into re-tubing the whole amplifier, or intimidate you into sending it back for the latest expensive modification. Buying more EL-84 output tubes remains a reasonable proposition as most brands list at under $50.00 for matched quads (4 tubes.) The providers include several Russian labels (all seemingly made at the same factory) and two other factories: the Slovak Republic (JJ Tesla) and the Ei tubes made in the former Yugoslavia. As for NOS, please check the Internet, with current prices starting around $25 for singles and quickly going up from there. The 12AT7's are easy to find with NOS starting at $25 per and up. The 6414 industrial types retail for less that $10.00 from www.tubesandmore.com or you can forget the entire search by buying everything directly from Manley.
"Tubes Rule!" don't you know?
But overall the Mahi - Mahi deliver a big sound for their size and power ratings. Once everything was in order and all systems were go, the Manley Mahi' delivered a magical big blooming image that was just great. Certain recordings were much better than others and had that inspirational sound that held you in your chair. With most recordings the imaging that was near realistic size with excellent depth. Mahis produce a beguiling sound that sounded best with classical pieces with older recordings taking on a new life—bounding out into my room like never before. Certain newer high quality recording techniques sometimes gave that bright over the edge sound that can wear you out quickly, but CDs that I tried from any of these labels were exceptional: First Impression Music; JVC XR-CDs; Harmonia Mundi; Hanssler; Delos, and Dorian.
Having the right equipment package is essential to getting the maximum performance with anything, and I would urge you to especially do your homework on the amplifier-speaker interface. With the Mahis, as with any other lower output amplifier, I would check out high sensitivity floor standers and look around for older English speakers that were voiced with lots of bass. The English seem to listen at lower levels in their small flats than we are used to here, and it is my guess is they desire some Flecther-Munsun curve bass boost right from the speaker itself.
Anyway, the Manley Mahis produce some magical tube sound with the right accessories, and the construction appears to be faultless. They are a well made American product selling at a fair market price. Their price is just above the Chinese import onslaught that will appeal to the "price is the object" crowd, which tends to preclude those who are looking and listening for "music is the object" gear. Meaning with the Mahis, you get both!
I highly recommend the Mahis with the right ancillary gear—especially with careful matching on the speakers. Les Mertz
Mahi - Mahi mono amplifiers