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May 2001
Enjoy the Music.com Review Magazine
Wavelength Audio Duetto Stereo Amplifier

Review by Ian White
Click here to e-mail reviewer


Mr. Taxman, fulfill my dreams... make her the biggest tax refund that I've ever seen... Mr. Taxman, I'm so alone... make it a Wavelength Duetto to call my own... Mr. Taxman bring me a dream!


Wavelength Audio Duetto Stereo Amplifier  For the past two months, I've genuinely struggled with what I was going to write about the Wavelength Audio Duetto, as I didn't want to go too overboard and put my foot in my mouth declaring it to be the "finest power amplifier that I've ever heard," only to find something better three months down the road. I would not be the first reviewer in history to do so, but I think calling something the "best" requires a great deal of comparison with comparable products and within a number of different systems. Very few of us have the time or resources to pull this off. That being said, I do think that the Duetto and its mighty eight watts (should be very popular with the power companies in California and New York this summer) can be compared to some non-audio related products to get a better feel for it.


"But Monsieur, it's just a little wafer thin…"

Ice cream connoisseurs will probably nod their heads when I suggest that listening to a device like the Duetto is akin to standing in line with the French and their kids at Berthillon in Paris waiting for that double-scoop of chocolate-nougat or glazed chestnut ice cream. It's very expensive, a real pain to have to wait for one, but that first lick is like dying and waking up in heaven, only to discover that Gerard Depardieu was kidnapped by aliens, the entire French national Football team was accidentally crushed by a large grape, and most of France's beautiful women are interested in you and ONLY you. The best part, unlike the fabulous ice cream at Berthillon, is that you only have to pay once.

With so many people jumping on the home theatre bandwagon (although it is starting to look like a very powerful locomotive), the staggering sales numbers for DVD, and the popularity of multi-channel five hundred watt amplifiers, it's probably puzzling to most why anyone in their right mind would want to buy an eight-watt single-ended amplifier. While it is easy to answer, "It's the quality of those eight watts," the fact remains that the majority of listeners are not prepared to make the necessary system changes to warrant such a purchase. If you are seriously interested in using a 300B, 2A3, or even 45-based single-ended power amplifier, you really need to seek out a number of different types of speakers to hear which one will best suit your listening tastes and your room size. While I am sure that there are some listeners out there whose listening tastes are limited to chamber music and Peter, Paul, and Mary, the vast majority of us listen to a rather extensive cross-section of music and there is nothing more frustrating than having an amplifier (especially, a really expensive one) crap out on you during the last thirty seconds of "Won't Get Fooled Again," "Higher Ground," or even the opening of "Sabotage," and "Root Down".

Over the past four years, I've listened to a lot of single-ended gear, and in a number of cases, the frustration set in during some dramatic moments (including some rather scary electrical shows involving steroid-induced triodes). Up until now, only the Art Audio Diavolo and the Blue Circle BC6 have really impressed me with their ability to play every type of music and through speakers of average sensitivity (88-90dB). The Diavolo, in particular, is absolutely mesmerizing with rock and even techno with speakers as small as the Meadowlark Kestrels and HotRod Shearwaters. When the Wavelength Duetto arrived, I was sceptical about its ability to keep up with the locomotive pace of the "Beast from the East" (fine, so Rhode Island is not exactly exotic…but it is east of Ohio), and with the speakers that I used, that proved to be the case. However, it was across the rest of the musical spectrum where the "little engine that could" sent the Devil and Saddam Hussein packing.


Is that a pocket-protector in your pants or are you just glad to see me?

While I have only had the pleasure of meeting Wavelength's Chief Scientist (it's even more amusing when you read it on his email), Gordon Rankin, once in the flesh, we've been emailing one another rather consistently over the past year and I think I have him figured out. Gordon is a perfectionist. By "perfectionist," I don't mean anal-retentive, but someone who is obsessed with the making sure that every last detail of his products is as perfect as humanly possible. The Duetto (8"H x 12"W x 14"D) looks less than imposing when you remove it from its hydrogen bomb-proof shipping container, but don't slack off when you remove it from the box. At 38 pounds, it is a lot heavier than it looks. Because I am anal-retentive, I spent about thirty minutes touching every last little inch of it and comparisons that came to mind were "Porsche," "Sig/Sauer," (for the gun wackos in the audience), "Brioni," and "Ms. Israel". It doesn't have the fancy faceplate of a Krell or the glossy look of a pair of Avant-Garde horns, but it's built to perform, and last a very, very, very long time. The base of my review unit was finished in a lovely dark walnut and the contrast between it and the black chassis cover and transformers made for a striking combination. Call it a beautiful piece of industrial art. When the tubes are illuminated, it becomes a very sexy piece of eye candy.

The chassis in neatly divided up into three sections: At the rear, you'll find a set of premium Cardas binding posts which have enough room for even the thickest of speaker cables and the Cardas output jacks allow you to connect your interconnects from above. The "python" power cord groupies will rejoice when they see how much room there is for one of their favorite power cords. The placement of all three allows you to route them away from one another, avoiding any potential RFI problems. Situated right in front of the posts, are a pair of 6SL7s, which are used in the gain/driver stage. Gordon will work with any potential purchaser to find the right 6SL7s to help achieve the sound you want. Occupying the middle of the chassis are three works of absolute beauty; power and output transformers from Philly-based (bet you're glad Bobby Clarke is still GM) Magnequest. While not the only factor, one of the reasons why the Duetto is not inexpensive is because of the quality of its iron. You wouldn't put a Honda six-cylinder in a Porsche, and the same logic applies when selecting iron for a single-ended amplifier. Finally, the front of the chassis is where you'll find a single NOS 5AR4 tube rectifier and the venerable classic, the Western Electric 300B.

Every Duetto is shipped with a matched pair of Western Electric 300Bs, unless of course you happen to be a stubborn reviewer from Canada who had to hear the new AVVT 300Bs instead of the WE 300B. For those who have to know more, the gain/driver stage uses a single 6SL7 in a modified SRPP circuit which is capacitor coupled to a 300B in a self-biasing configuration. The power supply uses not one, not two, but ten Black Gate capacitors. The power supply is rectified used the 5AR4 and is filtered through a simple PI network configuration. Both channels have their own power supply chokes to better separate the channels. The filaments of the 300B's are DC regulated to keep hum to a minimum.

Listeners who are not really interested in the technical mumbo-jumbo probably didn't flinch when I mentioned that that Duetto's power supply uses ten Black Gate capacitors, but one night while you are listening and you marvel at how this eight-watt amplifier rises to the occasion with even the most complex orchestral material, remember that little tidbit of information. On the noise level, the Duetto exhibits a tiny bit of transformer hum during the first minutes of start-up, but I found it inaudible during any listening and of all the tube gear I've ever tried, it's the quietest by far. From a reliability perspective, I've left the Duetto on for weeks without turning it off, which may not be great for tube longevity, but it has never made a single scary noise or even burped once.


Meet the new boss...

If you follow the logic that makes audiophiles tick, people buy single-ended amplifiers because they "are magical in the all-important midrange". Well, that may be the case as a generalization, but what about the rest of the audio spectrum? Last time I checked, the treble and bass were important as well. If I have one complaint about a number of the 300B and 2A3 single-ended amplifiers that I've heard, it is that some of them do sacrifice pace, dynamics, and a taut low end for that sacred cow - the midrange. In a $900 amplifier, I don't think that I'd care as much, as long as the product was way above average with the human voice and wasn't too slow sounding. In a $5,000+ product, those shortcomings become a serious problem and a reason why I'd have to say "thanks but no thanks". A $5,250 single-ended power amplifier has to be better in my opinion to justify its existence, especially when it only puts out 8 watts and can only be used with a limited group of speakers. How did the Duetto fare? Well, I guess that is the $5,250 question...

I've been fortunate enough to work in radio since the age of nineteen and I must confess that I'll probably never stop listening, no matter how few good stations survive. The quality of FM radio in Toronto has been on a downward spiral for a number of years, but a few gems still survive on the edge of the dial and the Duetto made me sit up, put down whatever book I was engrossed in and really pay attention to what I was hearing. My Naim tuner is no slouch, but I've never used it for anything more than late-night background music and I usually fall asleep with it on, only getting up to turn it off at around 4 in the morning. After about a week of listening to the Duetto, I came to the realization that I was listening to the radio almost three hours per night, seven days a week. No amplifier had ever made me do that before. Classical music in particular, sounded cleaner and had a lot more depth to it. Switching to jazz (CJRT 91.1), I was totally amazed at how well horns came across, with all of the necessary energy and pace. Eric Dolphy and I have become reacquainted and not a moment too soon.

If I had to pick one thing that made the Duetto improve the sound of FM radio as much as it did, it would have to be its superb tonal reproduction. The Duetto made the human voice sound more real than any other amplifier that I've ever tried and it did so without sacrificing pace, dynamics, or sounding rolled-off at the frequency extremes. Pushed too hard, the Duetto did bottom out a few times with my Spendor SP2/3s and Meadowlark HotRod Shearwaters, but neither speaker falls into the high-sensitivity crowd (both are between 88-89dB and stable 8 Ohm loads) and I've yet to hear the Duetto with horns or something more efficient like the Ocellia Kedros or Soliloquay 6.3.

From a presentation perspective, the Duetto was surprisingly more laid back sounding than any other single-ended amplifier that I've heard such as the Art Audio Diavolo, which now sounds aggressive to my ears. The Diavolo isn't so overly aggressive that I find it hard to listen to, but in comparison, the Duetto's sound could be described as being both immediate and very natural. The Duetto isn't fatiguing to listen to at all and it certainly doesn't favor one type of music over another. Its laid-back presentation is very much like a crafty pitcher who throws you two off-speed pitches before sending you back to the dugout having missed a called third strike that was waist high and past you at ninety-five miles an hour. It's a very tricky animal that will surprise you with its ability to provide music with vibrancy and attack when required, or become mellow when the mood changes. Very few components have the ability to do both of these really well. The Duetto is exceptional at both.


And Greenberg sends another one onto the roof of Tiger Stadium...

I usually listen to the same dozen or so CDs while reviewing a component, but the Duetto wasn't interested in anything as boring and simple as that. No, it demanded that I pull out some of the stranger recordings from the 1300 in my collection and have fun for a change. I spent hours listening to Sheila Chandra, Brave New World, Ofra Haza, Willie Nelson, the Everly Brothers, Elvis, Dvorak, Green Day, and one recording after another showed up another strength of the Duetto.

On material such as Green Day, the Duetto did a superb job at reproducing the bass guitar and Mike Dirnt never sounded as if he was being constrained or hindered as long as I didn't push the system too hard, which I did do on occasion. The Duetto can be pushed rather hard with a lot of music, but you need really efficient and dynamic speakers if you want to hear Green Day, Metallica, or The Who at very loud levels and without a breakdown in the bass department. With speakers that are only 89dB efficient, you can only expect so much with eight watts. The Duetto is a great amp for rock and alternative due to its wonderful tonality, clarity, and pace, but within reasonable listening levels. Jazz and blues recordings almost begged to be pushed and the Duetto rose to the occasion each time.

If you don't listen to vinyl (and I think you should), and you are sitting on the fence when it comes to buying a single-ended amplifier, I highly suggest that you get off of the fence and try an amplifier such as the Duetto with a decent entry-level turntable such as the Rega Planar 3 and a good MM or MC cartridge.


How good is the Duetto with vinyl?

Miles Davis' Nefertiti [Columbia Records PC9594] is not exactly my favorite jazz recording (truth is I can't stand hearing his name mentioned as I never understood his ridiculous anti-Semitic views), but the quality of the music and the recording was absolutely stunning with the Duetto driving the Spendor SP2/3s. The immediacy and presence that I felt demanded that I turn the volume up and I felt completely and utterly enveloped by the sound. I could almost feel Davis, Shorter, Hancock, Carter, and Williams in the room with me. Reviewers tend to throw that image around quite a bit in their comments, and I have often wondered if we were really hearing what we claimed to have heard. In the case of this recording, the Duetto was beyond extraordinary. The soundstage extended from one edge of my room to the other and with a pair of Spendors that is a rather large accomplishment as they not known for their ability to sound so unrestrained.

When I switched over to Charles Mingus' Mingus Dynasty [Columbia CL1440], I was really impressed by the warmth of Mingus' bass playing and the pace of the recording. The recording moved with a sense of purpose from one track to another and it was a no-brainer to flip it over and listen to the entire recording a second time.

During the review process, I purchased more than one hundred records and I think that says it all. When a component makes you hungry to find new music and not necessarily from artists or styles that you've liked in the past, it's providing you with more than just a fine listening experience, it's providing you with an education and a most valuable one in my opinion.


Who should consider trying the Duetto?

If you are willing to sacrifice some volume and bass slam for detail, tonality, depth, presence, and truly wonderful music reproduction and don't mind trying a few pairs of speakers until you get the right combination, I don't see how you could lose trying this piece of gear. The Duetto is built like a tank, is way more reliable than other tube gear that I've tried, sounds better with time, makes vinyl sound even better than you imagined, and is backed by a guy who would fly to the moon for his customers.


Just how good is the Duetto?

I've seriously only wanted to own three really extravagant things in my entire life; a house on a hill overlooking the Old City in Jerusalem, a Chagall painting, and a legitimately high-end piece of gear so superior to its peers that I would never part with it for any reason.

I'm one third of the way there.



Sub-bass (10 Hz - 60 Hz)


Mid-bass (80 Hz - 200 Hz)


Midrange (200 Hz - 3,000 Hz)


High-frequencies (3,000 Hz on up)






Inner Resolution


Soundscape width front


Soundscape width rear


Soundscape depth behind speakers


Soundscape extension into the room




Fit and Finish


Self Noise


Value for the Money



Manufacturer's Reply

I would like to thank Ian for his stunning review. I would like to empathize that leaving tube equipment on 24/7 is not in your best interest. This is particularly true when you receive a Wavelength amp. The exclusive techniques used in the output transformers will not reach their final break-in unless the amp is turned on and off in a typical manner. Turning off the amplifier will also save you $ on those expensive WE300B's and in the case of power outages the Mullard 5AR4 also. The Duetto reaches full listening in about 15 minutes. Thanks again to Ian and the rest of the crew at EnjoyTheMusic.com™.

Gordon Rankin
Chief Scientist and Owner


In Addition...

In the Wavelength Audio tradition there have been very few upgrades. I feel that it is best to invest time upfront on a product so the customer, dealers and the everyone else is not bothered by the inconvenience of upgrades.

The Duetto was introduced at the 1995 CES and therefore has been for sometime a product of stature within the line. At the 2004 CES in January at Alexis Park 1810 (new room this year) we will introduce the Diamond Duetto Integrated 300B amplifier. This will be a remote controlled new version of the Duetto on a heavy chrome chassis and Black Diamond Racing base. The tube compliment will include the TJ Mesh 300B, TJ 274B and a array of input tubes. As in the past many Black Gate capacitors will adorn the design as well as custom magnetics from MagneQuest. Please stay tune for more information at our website.

J. Gordon Rankin
Chief Scientist & Owner
Wavelength Audio, ltd.



Tubes: 6SL7, 300B, 5AR4

Input Impedance: 100K

Output Impedance: 4 or 8 ohm switchable

Power Output: 8 watts

Bandwidth: 15Hz to 45kHz (-3dB @ 1 watt) 

Size: 8 x 12 x 14 (HxWxD in inches)

Weight: 38 pounds

Price: $5,250


Company Information

Wavelength Audio 
4539 Plainville Road
Cincinnati, OH 45227

Phone/Fax: (513) 271-4186
Website: www.wavelengthaudio.com













































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