Posted: 23 Feb 2002 04:44 Post subject:
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Introduction - I will try to be as open and honest in this review as I can. When I first decided to purchase the nOrh Multiamps it was because I wanted to get the ultimate in 2-channel music reproduction at an affordable price. Anyone who wants to be an audiophile knows that affordable is a very relative term, and screams and shouts can be elicited from significant others and friends, merely by revealing what affordable translates to in actual money. I have since learned that the $1700 for the pair of Multiamps is pocket change in the realm of audiophilia. Keep in mind that Norh products are the only high-end products that I have spent any time with. I have heard other products in showrooms/listening rooms, and at friends’ houses.
When I ordered these amps with my Marble 9.0s to take advantage of special pricing, I could not also afford a high-end preamplifier or a high-end CD player, but knowing I could make do I went ahead with the pair of Multiamps. I could only use a single Multiamp with the high level inputs setting, because I had only a Yamaha receiver with no pre-outs. To my chagrin I had to rotate the 2 Multiamps just to burn them in. Still, the sound was much better than my Yamaha receiver. My friends and I were suitably impressed that I had made an improvement, even without the preamp in the system.
The day I received my CD-1 and ACA was the day I blew up both of my Multiamps. The act of moving them around sheared the amplifier chips a bit, and one chip actually exploded. The others merely smoldered a painful death. This phenomenon became a known defect of the Multiamps, and many were recalled for modification. A stiffening of the case, so that the 2 chips were not pulled away from the heat-sink, was required for the use of these amps. I believe the only defect that was encountered with the Multiamps that had been shipped. Soon no additional Multiamps shipped from nOrh, so that the remaining inventory could be used for replacements. No more Multiamps were manufactured due to this and other issues. The story can be read in the forums if you are interested. The important thing is that nOrh stood behind their products 100%, and so I now have my Multiamps returned to me BETTER than new.
Here is what was done to them: 1) The case was stiffened so that any flex was completely eliminated. 2) The amp chips were given a better thermal coupling to the large heatsink. 3) Some of the filter Fc points were adjusted to be in tighter spec. 4) Of course all amps were retested. These steps were taken by Curt of IRD, nOrh’s partner in the Le Amp and future preamp and crossover projects.
When I looked them over they were cosmetically flawless. They are chunky, manly looking amps, so they may not win the coolest looking amp contest. But they look to me like audiophile equipment I have seen in the past, and I am fine with the form-follows-function approach. The back panel could win an audio-geek award in any case(see photo). New brackets were added internally at the corners and this case does not flex at all.
Stereo Mode
Stereo mode means one 2-channel Multiamp powering the Marble 9.0s with the internal, passive crossovers connected in my system. (This is how the 9.0’s come from nOrh, with the option to do active biamping built into the cabinet.) They sounded fantastic to my ears. Every bit as good as the UN-modified Le Amps. Maybe a little better in mid-to-high, maybe a little worse in the bass, but it is hard for me to judge yet. It will take weeks or months until I feel comfortable giving my judgement. In any caser I will compare them to the modified Le Amps when I do.
Conclusion: Excellent as a 2-channel amp, but more expensive at $850 than 2 Le Amps for $500. Roughly equivalent to 2 Le Amps in performance, not at all surprising considering that many of the key components are identical and the design philosophy was the same. Except for the case, where Le Amp is a legend in its time.
Active Biamp Mode.
Yes, this is why I bought them in the first place. In a nutshell biamping means that instead of splitting the power amplifier's signal, you split the preamplifier's signal and send each half to different power amplifiers. So the left channel goes to the left speaker’s amplifiers, and likewise for the right channel. Unlike a monoblock setup powering speakers with internal crossovers, an active biamping gives each driver its own amplifier, which receives only the frequency range it is best suited for. The electronic, external crossover which allows this is built into the Multiamp, so that for $850 you get an active crossover and 2 amplifiers each with their own power supply. (In stereo mode each amplifier and power supply handles on stereo channel). This makes the Multiamp a real bargain when you want to do active biamping.
So going active meant that I first had to modify the Marble 9.0s by connecting each driver directly to the pair of binding posts which are standard on these speakers. This is a chore if you are not a hands on kind of guy, but par for the course in the audiophile world where some folks delight in building their own crossovers. I give it a 7 out of 10 for difficulty, because you need non-standard tools (metric hex wrenches) and you need to be VERY careful handling these expensive drivers. Then there is the need to be creative when placing the drivers back on their retaining rings which don’t want to stay glued to the marble baffles…I will do a separate topic on removing and replacing these drivers with photos, including the rewiring that is necessary for converting between crossover configurations.
Next I needed to plan the switching and connections to each Multiamp. The instructions from nOrh could be a little clearer. It takes reading them a few times as well as reading the instructions on the Multiamp itself to feel confident that the whole thing won’t explode again when you power it on. Just kidding, but you get the idea. Your speakers could be damaged easily in this endeavor so it is a must to understand completely what you are doing. In all fairness, if you take it slowly and carefully, the Multiamps literally will light the way for you. LEDs indicate where the polarity of the tweeter is reversed from the other modes, since you are now plugging the tweeters red (positive for me) connector into the black binding post. Of course, don’t plug WHILE the LED is lit - look at the LEDs with no cables plugged in, with the selector switches set for active mode, then note where the cables will go.
When I first powered up and played Steely Dan’s Aja, I knew I had a winner. Presence, power, and resolution were what came to mind. Low mid and high were all substantially improved, and the Scanspeak drivers can handle it all.
Practicalities of implementing and reviewing - Going back and forth between active biamping and passive crossover setups is very difficult. 4 drivers must be removed and internal wires must be located and reconnected. This means there is a substantial amount of time between comparisons, and audio memory is somewhat fleeting. Also you need twice the speaker cables. The general differences are obvious. I feel it will take me several months more to be able to report on all the differences. But here are some impressions I have so far….
Random thoughts on sonic benefits - Attack and decay of instruments are more realistic to my ears. The reverb effect which is present in most modern studio recordings is deeper stronger and tighter. There is a very strong perception that the sound is not trying to force its way through a passive crossover, but flows unhindered from the speakers. On Aja, cymbals are used the way they should be used. Steely Dan used lots of first-class studio musicians and did not apologize for it. This guys cymbal play as reproduced with active biamping brings tears to my eyes, and one reason Aja is an audiophile favorite. Brass is also pure and sweet. Kick drums are fuller and tighter. Lots of the guitar (my instrument) was just purer. The tweeters seemed to be a little more directional.
Vocals - Moxy Fruvous and Take Six are good tests of male vocals, with mostly a cappella recordings and precise and intense harmonizing. Listening to these CDs led me to set the tweeter attenuation to 4 clicks, which may or may not be the expected 6db. I will be looking into this. Female vocals such as Diana Krall’s “Peel Me a Grape” and Natalie Merchant on 10,000 Maniac’s In My Tribe seemed to come more from the diaphragm and were very resolved. Diana Kralls vocal seemed a little “hot” on some tracks, but all the details are more apparent.
XRCD Jazz - Tom Coster From the Street - wow. On the CD-1 this has great resolution anyway. Biamping features of power range and less distortion really come out with this CD.
Naxos Best Of Ravel “”Bolero”. One of my favorite classical pieces because of the variety if instruments taking the lead, the hypnotic and complex melody, and the “bells” floating above which Ravel created with harmonics. This recording leads me to belive the Le Amps could do better with the bass than the Multiamps, but I will have to do more comparisons with them in the future.
Conclusion: Active is the way to go. More power, less fluxuating power, less distortion, more “presence” are all the things I notice. The Multiamps are well worth the money now that they have been repaired and improved. An excellent product from nOrh, that definitely gives an audiophile bang for the buck.
