|All In Your Head
August 2006HeadRoom Desktop Millett Hybrid Headphone Amplifier
by Eric Hetherington
I know a professor of German literature and philosophy who is consumed with the idea of "play." For him, the notion that you can change the meaning of sentences by playing with their placement in relation to other sentences or even change the meaning of whole books by placing sentences in different contexts is endlessly fascinating and amusing. His goal, though, isnt simply to change the order of words on the page; rather, he thinks that examining the way words can interact and how that activity can change or challenge our ideas leads us to think of things in new ways. He has an awfully good time "playing" in this way, and hes almost always in a good mood.
This notion of "play" seems similar to the activity of audiophiles who swap the tubes out of their amplifiers partly in hope of finding a better-to-them sound, but also just because it is fun. Both the tube lover and my German friend take pleasure in the activity itself, even if the rewards are not always easy to discern.
While HeadRoom has been around for years, the Desktop Millett Hybrid is the company's first headphone amplifier to use tubes. It is based on a design by Peter Millett that has been highly praised by do-it-yourselfers, but the Desktop Millett Hybrid has been co-developed by Millett and HeadRoom. You can see more of Milletts work on his website, www.pmillett.com. Be warned: If you have DIY experience you might just find a new project to undertake, as Millett has several designs on his page that hes released in the public domain. The output stage of the Desktop Millett Hybrid is solid state, like that of other HeadRoom amps, but your music passes through a low-voltage tube line stage beforehand.
The $649 USD Millett Hybrid measures 6 1/4"W by 3 1/4"H x 6 ¼"D, not including the tubes, which stick up, or the volume knob, which sticks out. The front and back have a slightly convex curve to them, and the case is rounded with no sharp corners. On the top of the case there are two holes where the tubes reside. Near the left-front corner of the unit is the small power switch, which also turns on the green LED in the HeadRoom logo right above it. Next come two outputs for your headphones, 1/4" and 1/8". Previous amps from HeadRoom had only had 1/4" outputs as that was de rigueur for headphones, but the proliferation of the iPod and similar devices has made the 1/8" connector much more popular. It may be a small thing, but as someone who occasionally had to search through drawers and boxes for an 1/8"-to-1/4" adapter, I liked having the two outputs.
The outputs are followed by four small switches. The first of these controls a pair of RCA outputs on the rear of the unit. These allow you to use the Desktop Millett Hybrid as a preamp, but you can turn them off if you only plan to use it as a headphone amp. The second switch is for tube selection; you can choose between different tubes (more on this below). The third switch turns on HeadRooms crossfeed circuit (more on this below too), and the fourth allows you to set the gain presented by the amp (low, medium, high). Different headphones have different power needs, and the gain switch allows users to tailor the amp to them. The final feature on the front is the volume control.
There are four features on the rear of the Millett Hybrid. First is an input selector to choose between the two inputs available on the amp. I wasnt crazy about the placement of this selector because, depending on where you place your amp, it isnt always easy to get to the rear panel. Im sure there are good design reasons against it, but I would have liked to see the gain switch on the back and the input selector on the front. Right next to the switch are the two sets of RCA inputs, and they are followed by another pair of connectors for the RCA outputs. On the far right is the input to connect with the "brick" power supply included with the amp.
The 12FM6, 12AE6A or 12FK6 tubes (that's right -- you have your choice) were originally designed for use in car stereos. Possibly because of this, the tubes are rugged and dont require the user to bias each separately. Still, each tube is a little different and the tube selector switch on the front sets the bias for that particular tube. This is a user-friendly feature and makes the amp good for tube newbies who dont know how to bias a tube.
Of course, if there is no sonic difference among the tubes, such flexibility would just be a waste of time. There are differences, but they are subtle, and I imagine that it would take some time before a listener could discern which tube is inserted without looking. HeadRoom describes the 12FM6 as "laid-back and warm," the 12AE6A6 as having a "liquid midrange," and the 12FK6 as "neutral." I wouldve liked to dive in to comparing the tubes, but good writing demands economy, and, with two small children, I only have so much time.
The HeadRoom crossfeed circuit is intended to help the listener with fatigue that may result from the unnatural nature of headphones. When you listen to speakers, both of your ears hear both speakers, but this is obviously not true with headphones. Because of this, headphones can cause fatigue based on the localized nature of the sounds. The crossfeed circuit feeds a little of the left signal to the right and vice versa to better approach how our ears and brains usually function. This is particularly useful with older recordings in which the instruments are hard-panned into the right and left channels. On some recordings it is indispensable, while for others it is not necessary. My suggestion to the user is the same I had with the gain switch: experiment.
The Desktop Millett Hybrid is a beautifully constructed piece of gear, and the good folks at HeadRoom have made it a piece the user can retain even when he becomes infected with upgrade fever. There are three upgrades available. First, you can upgrade the electronics module from the standard Desktop Hybrid module to the Home Hybrid module for $99. The Home module runs in class A and adds additional output buffers. Second, the volume control can be upgraded from the Nobel potentiometer that is standard to a stepped attenuator that may help the user get that last little bit of performance out of the amp. The final upgrade possibility is the Desktop power supply, which is $399 and can provide power for up to six components. I did not have one on hand, so I cant comment on the improvement, but it should help with important aspects of the amps performance, such as its detail retrieval and dynamic ability.
I used the HeadRoom Millett Hybrid in a system with a Rotel RCD 1070 CD player and Analysis Plus Silver Oval-In interconnects, Grado SR-60 headphones, and Etymotic ER-4P in-ear monitors. My iHome bedside radio, which doubles as an iPod dock, has a line-out that I also connected to the HeadRoom amp for casual listening. All of my review impressions come from listening to the Rotel CD player, but the iPod connection was convenient for late-night and early-morning sessions. I kept the 12FK6 tubes installed and used the Etymotic ER-4Ps for my more critical listening just to cut down on the number of variables. If I was listening for fun, Id change tubes more often and with different kinds of music to discover what combination would be just right.
One thing about the amp that may be of concern to those new to tubes is that, depending on your headphones, there may be a hum or buzz when no signal is present or when the music is quiet. Ive noticed this with every tubed headphone amplifier Ive used, so it isnt just with the HeadRoom design.
Ive been listening to a lot of '60s-era Miles Davis lately, especially the work that led up to the recording of Bitches Brew. The three-disc The Complete In a Silent Way set [Columbia C3K 65362] includes some great music, including the unedited takes from which the original album was composed. Via the Desktop Millett Hybrid, "In a Silent Way (rehearsal)" and "In a Silent Way" from disc two produced a laid-back sound with a nice warm tone on the trumpet and electric guitar. The percussion had the right "snap" to it, especially Tony Williams hitting of his drum stick against something hard. On "Mademoiselle Marby" from disc one, the bass seemed more reticent and shy than Im accustomed to hearing, but I could easily close my eyes and see the bassists fingers moving over the strings. Overall, I found that the extreme ends of the musical spectrum werent being given their due, but the presentation was so smooth and listenable that I didnt care.
One good side effect of reviewing audio components is the excuse to listen to Johnny Cashs American Recordings albums. The concluding track on American IV: The Man Comes Around [American 440 077 083-0], "Well Meet Again", offered a nice vocal challenge for the Millett Hybrid amp with a closing chorus of many singers. Each voice was clearly delineated from the others, and the clarinet throughout the song sounded almost dead-on, but lacked a little of the heft that a real instrument would produce. Cashs take on "Danny Boy" from this album gave the HeadRoom amp a chance to produce the difficult sound of an organ. Obviously, headphones cannot offer the same physical effect an organ can have through loudspeakers, but the Desktop Millett Hybrid had no trouble conveying the ebb and flow of the music and Cashs resonant voice. This presentation highlighted to me something that HeadRooms Tyll Herstens is fond of pointing out: You dont get the physicality of loudspeakers with headphones, but you do get increased awareness of detail.
Of Montreals latest album, The Sunlandic Twins [Polyvinyl PRC-088], is a wonderfully psychedelic experience. My favorite track, "Wraith Pinned to the Mist and Other Games," has a driving bass line that sounded smooth and buttery on the Desktop Millett Hybrid. I adore the sing-song chorus of "Lets pretend we dont exist; Lets pretend were in Antarctica," and I found that I was listening to small details of the mix that I had missed through my speakers, such as the number of vocal tracks involved and small beeps and blips that are easy to overlook with speakers. The same album's "Forecast Fascist Future" opens with some rock guitar that sounded meaty if still a little polite.
The Desktop Millett Hybrid presented music in a mellow vein. It favored the flow of the music over an up-front, analytical presentation. Because of this, it seems particularly suited to people who listen for long stretches of time. You can certainly sit back and listen to details in the music, but those details arent up in your face the way some amplifiers present them. One thing I noticed throughout my time with the Desktop Millett Hybrid was that I listened to more of the CDs I was playing than I needed to. Often, I make a list of songs that I think will be useful for reviewing purposes and then listen to those songs without playing the rest of the album. I usually turn the music off while I compose my thoughts for each track, but I found myself keeping the disc playing and listening to more songs on each album -- never a bad thing.
I had two other headphone amplifiers on hand to which I compared the Desktop Millett Hybrid. First, I had HeadRooms own Micro, a new model Ive reviewed on SoundStage!s sister publication, GoodSound! The other was Benchmark Medias DAC1. By now it seems that everyone has heard of the DAC1, and you can see my review of it on GoodSound! too. I tried to keep the systems as constant as possible, but because of the available connections, some changes had to be made. First, The Micro only has a 1/8" input, so I was forced to use an RCA-to-mini-plug cable with it. Second, the DAC1 only accepts digital inputs, so I fed it a signal from the disc player using a DH Labs D-75. For a different listening experience, I also connected the Desktop Millett Hybrid to the RCA outputs of the DAC1.
Sonny Clarks Cool Struttin [Blue Note 7243 4 95327 2 4] is a classic Blue Note album, and its opening track provided a pleasurable way to compare the Desktop Millett Hybrid and the Benchmark DAC1. Remember when I mentioned amps that get up in your grill (as the kids say) with analytical detail? I find the DAC1 to be that way, and I like it. I love hearing every little detail. When I listen to music, Im usually doing nothing else, so I like an up-front presentation. The Desktop Millett Hybrid seemed to emphasize the overall musical flow, while the Benchmark DAC1 gave me every last bit of detail. The HeadRoom presented a soundstage that seemed farther away from me, as if I were watching the band play from the middle of the club, while the Benchmark put me in the first row. As might be expected, because of this, the instruments seemed bigger through the Benchmark DAC1, but the soundstage seemed slightly more coherent with the HeadRoom amp.
The HeadRoom Micro is the Desktop Millett Hybrids little sibling. Able to be run on two 9-volt batteries and the perfect size to accompany an iPod, the Micro has become my favorite portable headphone amp. The sound of the two amps is similar, but the bigger sibling wins in some important categories. The Desktop Millett Hybrids sound was more organic and three-dimensional whereas on some tracks the Micro gave me a flat presentation. It also simply sounded like there was more "oomph" behind the music with the Desktop Millett Hybrid. While listening to the Beach Boys' classic "Little Honda" from Little Deuce Coup/All Summer Long [Capitol 72435-31516-2-1], I noticed that subtle parts of the mix were more distinct with the Desktop Millett Hybrid amp, and the guitar strumming in the right channel sounded like it had real physical weight behind it. Still, you cant carry the larger amp to work with you or take it to the beach. I imagine for most people the Micro presents a better cost: benefit ratio, but people looking for a tubed headphone amp probably dont have that as their first priority.
When it comes to headphone amps, the kind of amp a user wants is intimately tied to how he uses headphones. If you want something you can travel or commute with, then the HeadRoom Micro may be your best bet, and it will do justice to both office and home listening. Dont want to bother with tubes and want a one-box DAC/amp? The Benchmark DAC1 will suit your needs. If a DAC/headphone amp is your hearts desire, you should also know that HeadRooms non-tubed Desktop, Home and Max models can be fitted with a DAC module. Unfortunately, I havent heard them.
But, if you like to tweak and change the sound of your amp, then the Desktop Millett Hybrid might just be for you. If youve never owned a tubed headphone amplifier, the Desktop Millett Hybrid is a good-sounding starting point. It has a sweet sound that remains enjoyable after hours of listening. Its flick-of-a-switch biasing and gain switch make it easy to tailor it to your preferences rather than having the amp dictate your tube and headphone choices. I like that HeadRoom supplies three different sets of tubes to play with, and the attention to design details is first-rate. You can spend hours playing with the tubes and seeing how they affect the sound. Maybe youll find a tube that sets your heart on fire, or maybe, like my German friend, youll just enjoy playing for its own sake.
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