HeadRoom Maxed Out Home Headphone Amplifier
amp type: Bi-Polar
input impedance: 100,000 ohms
maximum gain: 6.0v
output power 30 ohms: 250
output power 300 ohms: 250
THD, 10mw, 30 ohms: .0014
crosstalk, 10mw, 30 or 300 ohms: 95 dB
output stage biasing: A/B
output impedance: .0150
output voltage at clipping: 12.7v
output power, 100 ohms: 325
THD, 10mw, 30 ohms: .00260
THD, 10mw, 300 ohms: .00087
crosstalk, 10mw, 100 ohms: 94 dB
dimensions: 12 L x 6 3/4 W x 2 3/8 H
weight: 5.6 lbs.
521 East Peach Street
Bozeman, MT 59715
HeadRoom is the specialist outlet in the world for headphones, headphone amps, portable carry cases for them, and every imaginable accessory connected with headphones. Their catalog and website present a dizzying array of products both of their own design and from leading manufacturers of headphones as well as other makers of headphone amps. All of their own models are hand-built in Bozeman. The listing of dedicated headphone amps is arranged from their most basic entry-level model at $119 to their no-holds-barred esoteric BlockHead amp with enhanced stepped attenuators, at $3888.
The various iterations of the Maxed Out Home model are nearer the high end of the list. Between it and BlockHead is the just plain Max, which has a more expensive power supply, better matching of components, and fancier machined front and back panels that increase the cost to the $1600 area. The general idea is that the Maxed Out Home represents a good balance between price and performance.
Ins & Outs
The Maxed Outs are available with two different input/output configurations. The model at hand has two sets of L/R input jacks (selectable with a rear-panel switch), but you could also get one with just a single input jack set and the other two jacks become a L/R Loop Out - so that the Maxed Out can be inserted into an existing system between the tape-out of the preamp and the record-in of a DAT/Minidisc/CD or DVD recorder.
The Maxed Out comes with HeadRooms Reference Electronics Module as standard equipment - more on that in a moment. In addition, a higher performance stepped attenuator upgrade is available at additional cost, as with the super-high-end BlockHead amp. The units heavy-duty case is finished in an anodized extruded aluminum in black. It would look great sitting on top of a CD or DVD player or a preamp as long as it is cool running. The rear panel sports, from left to right: the detachable AC power cord socket, the on/off switch, a fuse, a mini-toggle switch to lift the ground to minimize 60 Hz hum (I needed this float option - bad hum in the off position), the Input 1 and Input 2 jackets with another mini-toggle switch located between them to select either one, and lastly the L/R Output Jacks. The RCA jacks are more heavy duty than those on the back of most reasonably-priced home theater preamps and receivers; you wont ever have to worry about pulling off the entire shielding portion of the jack if you have snug-fitting audiophile cables. The power supply uses a Talima toroidal mains transformer and + /- 15v DC series pass regulator type design, using Linear Tech high-speed, low-noise regulators.
Now moving around to the front of the Maxed Out: Starting on the left we have two exceptionally heavy-duty Neutric stereo phone plug jacks. You have to press a small level to open the connection and lock the plug in the jack. Next to these are three more mini-toggles. They are respectively for Filter, Process and Gain. Starting from the right, the gain setting has high, low and medium options to handle whatever varying input levels you have from your other component and whatever sensitivity the particular headphones youre using happen to have. Next to the Gain is the smooth operating large-knob Nobel pot level control and a red on/off LED.
Process and Filter are tied in with HeadRooms special audio imaging circuit which is honored in the name of their company as well as a feature that they have promoted in all their headphone amps since they were founded. Since stereo recordings are designed for loudspeaker playback and not headphone playback (as are binaural recordings), listening on any headphones to stereo material always results in a rather bizarre sonic effect. (Never mind that its possible to get better fidelity in general with headphones for a lot less investment than with quality loudspeakers.)
The main problem with stereo on headphones is that all the sounds occur instead ones skull. With true binaural recordings and proper matching of the original mike, headphones and the hearing of the particular listener, it is possible to image the sounds outside of ones head with amazing realism. With stereo this is impossible; most people hear the left channel signal concentrated at the left side of their skull and the right channel over at the right side, with a hole-in-the-middle that is worse than with the most improperly-spaced stereo loudspeakers. The object of the HeadRoom audio image processor is to bleed off just a little bit of both the left and the right channel signals and mix them in phase so that they seem to appear in the middle of your skull - filling in that hole-in-the middle and creating a more seamless soundstage in your head.
My personal feeling from the earliest version of this circuit is that while it has some sonic advantages, it also exhibits some disadvantages in dulling the sound a bit. Fortunately HeadRoom has always provided an on/off switch if you prefer not to use the process. This time around HeadRoom has provided a fix for the dulling problem, and thats what the left-hand toggle switch is for: It provides a mild high frequency boost. Filter has settings of bright, brighter and off, so that the high end can be sloped upward to ameliorate the rolloff caused by the HeadRoom process.
I found the image processing circuit useful in listening to Billy Joels Fantasies and Delusions compositions for solo piano (Sony Classical SACD). I decided to use SACDs for all the test material, wanting to provide the Maxed Out with the maximum fidelity sources to work with.
The engineers for this disc evidently used the same exaggerated multimike approach heard on most piano recordings from major labels - meaning too many mikes and too close to the instrument. The result on speakers is a 30-foot-wide grand piano, and on headphones the effect is even more dramatic. So switching on the image processor filled in the center in my head and rather than shrinking the width of the piano made it sound more like my head was stuck inside the strings under the lid. However, there was still a dulling of the extended high end that spoiled the amazing realism of this piano sound - even when using the brightest filter option.
I see I havent listed which headphones I used with the Maxed Out. My high end favorites (as well as HeadRooms favorite) are the AKG K1000 off the-ear speakerphones. They require a lot of power plus a proprietary plug connection, so I couldnt use them with the Maxed Out. My reference headphone amp is the matching K1000 amp. I also didnt have a pair of the top-end HD600 Sennheiser phones which HeadRoom also recommends at their price point, but I did have the Sennheiser HD 433. My other workaday phones are the Grado SR-80.
Next I tried First Time! - the exciting meeting of the Ellington and Basie bands on Columbia Legacy SACD. The impact was tremendous, and in this case the huge separation of the left and right sides (without the processor) seemed to add to the musical excitement. The high brass overtones became a bit grating with the Sennheisers and were much more copasetic with the Grados. Leaving the Grados on my head and switching to the AKG amp produced more deep bass on the bass solos and less annoying brass sounds than with the Maxed Out. I also tried the Sennheisers and the brass still sounded agreeable.
I had been listening very closely on speakers to the multichannel layer of the new Hilary Hahn violin concertos SACD on Sony Classical (Brahms and Stravinsky Concertos). The reason was that I heard some cutting out of the center channel about 30 seconds into the initial movement of the Brahms D Major. For this headphone work I used the alternate stereo SACD mix, which didnt cut out a bit at that point. Hahn has a very silky violin tone in spite of the close miking used. However, with both headphones fed by the Maxed Out the violin tone was edgy and unpleasant. Switching either one to being fed by the reference amp corrected the problem. Switching on the image processor with the Maxed Out helped the edgy string tone but only partially.
I also tried feeding the Maxed Out directly from the Line Out of my trusty Optimus CD-3400 portable CD player (remember that sonic bargain? By the way, does anyone out there have a leftover wall-wart for one? - I know its supposed to sound better on batteries but this thing really eats em!) Anyway, the results werent that different from getting the input signal from my Sunfire Av preamp, except that none of the three SACD would play on it because they werent hybrid discs!
I havent given up on the Maxed Out as a result of my review. Theres a tremendous variety of possibilities between the input to a headphone amp and the headphones used with it. I can only observe that it would probably be a mistake to buy any headphone amp without trying it out with your system and your favorite headphones. You could get completely different results with different phones and inputs. The Maxed Out does seem to be a good choice balancing performance and price, and its built like a tank.
- John Sunier firstname.lastname@example.org
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