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HeadRoom Max headphone amplifier Page 3

Head of the Class
Articulate—that's the word that best describes Max. Oh, there are others: fast, rich, complex—and, paradoxically, simple as well. But articulate is the one that resonates most strongly. Perhaps I'm more sensitive to this than most, but for me, music is primarily about communication.

It could be argued that musical communication is compromised when the complete frequency range is slighted, or when transient edges are blunted—and I agree entirely. In fact, HeadRoom Max illuminates the frequency extremes with uncommon clarity. Its bass response is deep and full-bodied…

HeadRoom Max headphone amplifier Page 4

Listening through Max, I was intensely aware that both sets of voices—despite their seeming solidity—are not themselves physical entities, although they define that which contains them. You can hear through them—almost see through them—and when someone nudges a hymnal with their foot (at least that's what it sounds like to me), the scrape of the cover along the stone floor and the reverberations from that motion are startling in the way in which they define a specific point within all of that space.

Ultimately, however, I must keep returning to that least definable of qualities, but the…

HeadRoom Max headphone amplifier Specifications

Sidebar 1: Specifications

Description: Headphone amplifier with one set of inputs, one set of feedthrough outputs, two sets of headphone outputs. Power rating: 0.5W. Frequency response, THD, Crosstalk, S/N ratio: all not specified.
Dimensions: 6.7" W by 2.4" H by 12" D.
Serial number of unit reviewed: None on review sample.
Price: $1333. Approximate number of dealers: sold factory-direct only.
Manufacturer: HeadRoom Corp., P.O. Box 6549, Bozeman, MT 59715. Tel: (800) 828-8184, (406) 587-9466. Fax: (406) 587-9484. Web: www.headphone.com .

HeadRoom Max headphone amplifier Maxed Out

Sidebar 2: Maxed Out

After my auditioning was over, I asked Tyll Hertsens to explain the evolution of the HeadRoom Max:

Hertsens: Part of the reason that I designed the HeadRoom Max was that we became aware of some parts that had become available for the module—the Burr-Brown 627, which replaced the Burr-Brown 604 op-amp, and the polyphenoline-sulfite film capacitors, which replace ceramic caps. I made the Home HeadRoom as good as I could—I actually think the 604 is a pretty good op-amp—but we were limited in that we had to use surface-mount components. Up until six months ago,…

HeadRoom Max headphone amplifier Associated Equipment

Sidebar 3: Associated Equipment

Digital front-end: Audio Research CD1A.
Comparison headphone amplifiers: Audio Alchemy HPA v1.0, Home HeadRoom, McCormack Micro Integrated Drive, Melos SHA-Gold.
Headphones: Grado RS-One & SR-125; Sennheiser HD-580 & 580 Jubilee; Etymotic ER-4S; Beyerdynamic DT 911.
Interconnect: Monster M-1000i.—Wes Phillips

HeadRoom Max headphone amplifier Head to Head

Sidebar 4: Head to Head (From February 1998, Vol.21 No.2)

No sooner had I reviewed the $1699 Stax Lambda Nova Signature/SRM-T1W electrostatic headphones combination (Vol.20 No.6) than I began to receive letters from headphone listeners asking me to compare the Lambda Nova with Sennheiser's HD-580s driven by a HeadRoom Max amplifier. I thought a comparison between the Stax and the $1732 Sennheiser HD 600/HeadRoom combo would be appropriate.

First, the Staxes are a bargain—their $1699 price has been established by Audio Advisor from a "list" price of $3200. (Something about this…

HeadRoom Max headphone amplifier Measurements

Sidebar 5: Measurements

All measurements were taken from the HeadRoom Max's front-panel headphone jacks. With its very high input impedance (484k ohms) and respectably low output impedance (0.5 ohms at 20Hz and 1kHz, 0.55 ohms at 20kHz), the Max's performance is unlikely to be compromised by interface problems with associated equipment. Maximum voltage gain measured 12.3dB. DC offset was a highish 15mV in the left channel, 14.8mV in the right. S/N Ratio (ref. 1V out) measured 73.8dB at the maximum setting of the gain control, but improved to 84.2dB in the 12:00 position. The Max is…

HeadRoom Max headphone amplifier Measurements part 2

While the Max's 1kHz squarewave response is good enough to make its presentation here unnecessary, the 10kHz response in fig.4 clearly shows the HF rolloff indicated in fig.1. The crosstalk shown in fig.5 indicates virtually identical performance between channels, and the (deliberate) increase in crosstalk when processing is engaged.

Fig.4 HeadRoom Max, small-signal 10kHz squarewave into 100k ohms.

Fig.5 HeadRoom Max, crosstalk (from top to bottom at 10kHz): L-R, R-L with filter & processor on; L-R, R-L with filter & processor off (10dB/vertical div.).…

HeadRoom Max headphone amplifier Measurements part 3

The response of the Max to a 50Hz input at 2.5V output into 40 ohms is shown in fig.7: all distortion artifacts are below -90dB (0.003%). Harmonics of the power-line frequency are also clearly visible, but still more than 90dB down. Fig.8 shows the output spectrum resulting from an input signal consisting of an equal combination of 19 and 20kHz at an output of 2.5V into 40 ohms. The most significant artifacts here are at 18kHz and 21kHz (more than -66dB, or about 0.05%); the 1kHz difference tone is at -82.4dB, or about 0.008%.

Fig.7 HeadRoom Max, spectrum of 50Hz sinewave, DC-1kHz…

Kharma Ceramique CE-2.0 loudspeaker

Oh boy! This was one of my most eagerly anticipated auditions. At my first demonstration of an OLS loudspeaker system several years ago, I was bowled over not only by the demo, but also by the idea that OLS's Kharma line was topped by the $1,000,000 Grand Enigma system!

OLS has been in operation since the early 1980s, and for me, seeing the depth and variety of their product line was like discovering an unexpected continent of new possibilities. Shortly after my first audition, OLS began showing the Kharma Ceramique speakers at various shows, and were they ever seductive. Not only are…