Product Review (March 2007) Headroom
Desktop Amp Headphone Amplifier

By Kevin Nakano


HeadRoom has been dedicated to improving the sonic experience of headphone listeners by providing hi-end electronics to audiophiles willing to pay for it. Their product line is extensive and includes headphone amplifiers, digital-to-analog converters (DACs) and other accessories that make the audio experience something to remember. Luckily, there are a good number of folks out there that want to improve the quality of the audio electronics that drive their headphones and for good reason. There are just too many products out there that do not provide the audio quality one might expect especially when using headphones such as the Sennheiser 600 or AKG 701's that reveal amazing detail. The HeadRoom Desktop Amp is described as the "Swiss Army Knife" of audio and that is indeed what it is. The Desktop Amp is loaded with features that include a variety of standard digital inputs and analog interfaces. Analog inputs and outputs are available for those lacking a digital interface or simply if the analog source is preferred. This flexibility allows the Desktop to be used in virtually any setting including, but not limited to your home or office desktop. We connected the Desktop Amp to our office computer and a new level of audio enjoyment was experienced. The Desktop Amp measures 6 ¼” x 6 ¼” x 3 1/3” and weighs approximately 1.8 pounds.

Features
The front panel of the Desktop Amp offers the maximum in flexibility by providing users with a full-size 1/4" as well as a miniature 1/8” (3.5mm) stereo headphone jacks. The current drive is good enough to drive both headphone output jacks at the same time. Three types of digital inputs are available on the rear panel depending on your situation or preference. Since our desktop computer was being used as our audio source, we made use of the USB interface. The computer immediately recognized the Desktop Amp and did not require any additional software for it to operate. Two pairs of analog line level inputs as well as a single pair of variable level analog outputs are provided through high quality, gold-plated RCA jacks. The latter feature actually allows the Desktop to operate as a preamplifier complete with onboard DAC processing capability. A 3-position gain switch allows users to select different volume control ranges depending on the output level of the source. Depending on your tastes, a set of discrete crossfeed and filter switches are available to allow the user to adjust the type of audio processing HeadRoom is known for. The main power switch is also available on the front panel.

Rear Panel
The rear panel of the Desktop Amp has all the digital and analog interfaces and includes a 3-position digital input selector switch and source selector switch to choose between the digital and analog inputs. Since these switches are seldom used, HeadRoom made the decision to place them on the rear panel. Two independent sets of RCA analog inputs allow different sources to be connected to the unit. An input selector switch is used to choose between the two sets of analog inputs. A 5-pin DIN connector accepts ±15VDC power from the outboard linear power supply. While linear power supplies are less power efficient and heavier, they typically provide much lower noise and line ripple in the power. This reduces noise and increases performance of the the analog circuits that utilize them.

Design
The convergence of the poor sounding PC and the Audiophile has now morphed with products like the HeadRoom Desktop Amp. No longer do critical listeners have to put up with the often grainy sound offered by so many computer audio products. Rarely do outboard amplifiers alone produce good sound from an inferior DAC built in many computers. The HeadRoom Desktop Amp takes care of it all from the DAC to the headphone. Best of all, users can choose just how much quality they want to get out of their desktop setup since HeadRoom offers a variety of options.

Electronics Module Options
The basic Desktop Amp is fantastic as it stands, yet HeadRoom felt the need to offer better components for those who want to squeeze a bit more performance out of the unit. The first option customers should consider is the freshly-revised HeadRoom electronics module. It is most cost effective to have this installed initially rather than to have it changed later. The upgraded Home Electronics Module ($99) option makes use of the same Burr-Brown 2134 op-amps, but adds a series of constant current sources to force the amplifiers into full Class “A” bias. The result is a an ultra-tight sound with amazing musical detail and resolution over the entire frequency range.

Finally, the top-of-the-line Max Electronics Module ($399) is physically larger than the other modules to accommodate the single-amp-per-package Burr-Brown OPA627 op-amps. These precision FET (DiFET) operational amplifier are some of the best and most expensive audio op-amps available. But what is cost when trying to achieve audio nirvana. The Max module also uses gold coated, heavy 2 oz. copper traces with gold coating all on a four-layer circuit board.

Volume Control Options
If you are willing to get the Max Module, then you may want to consider the stepped attenuator volume control option. The sonic clarity offered by the discrete resistors design with the custom-made 24-position stepped attenuator volume control is superior. HeadRoom is always available should you need assistance in choosing the various options on your Desktop Amp.

Digital to Analog Converter (DAC) Options
HeadRoom offers the basic Desktop DAC ($249) that is based on the Cirrus CS4398 chip which is their top-of-the-line, flagship DAC. The CS4398 is a 120 dB, 24-Bit, 192 kHz Stereo D/A Converter with impressive performance. The CS4398 has a selectable fast and slow digital interpolation filter followed by an oversampled multi-bit delta-sigma modulator that includes mismatch shaping technology that eliminates distortion due to capacitor mismatch. The next stage is a multi-element switched capacitor stage and low pass filter with differential analog outputs.

HeadRoom also offers the same Burr-Brown OPA627 op-amps used in their Home DAC option ($299) and places the Cirrus CS4398 DAC unit into true constant-current Class "A" bias. This results in an improvement in overall DAC smoothness and musical detail resolution.

For the ultimate DAC performance, HeadRoom offers the Max DAC option ($399), which features a high performance Analog Devices AD1896 is a sample rate converter. The AD1896 chip sits between the digital receiver and the CS4398 DAC. It receives the incoming digital data from the digital receiver, stores it, up-samples it, interpolates it and then sends it off to the CS4398 DAC.

Desktop Power Supply
There is no doubt that Class-A operation draws a significant amount of current from the power supply and that is why HeadRoom offers the Desktop Power Supply (DPS). The DPS features voltage tracking regulator circuits that precisely and accurately responds to dynamic current variations. Six independent outputs located on the rear panel of the unit provide clean power to as many as six of your audio components using 5-pin DIN-plug power receptacles.

Performance
We used the Desktop Amp for several months and our desktop audio never sounded better. Even with sources that were a bit compressed using 320 kb/s MP3 files, audio sounded excellent. It became quite obvious that our factory DAC electronics in our PC was doing very bad things to the audio signal. By running the USB cable from our PC we heard incredible detail especially when paired with a set of A
KG 701 or Sennheiser HD600 headphones. We also enjoyed the new clarity we heard on our Shure E500PTH earphones.

We also connected the Desktop Amp to our PC speakers and heard a noticeable improvement in sound quality. While audio performance can vary widely between speaker systems connected to the PC, it was still clear that this front-end was making a huge improvement in sound quality.

Conclusion
The Desktop Amp is a great product that offers audiophiles improved sound quality for their laptops or desktops. The higher performance options will please the most critical audiophile. Our desktop actually became an enjoyable source for our audio and with the large disc capacity and internet access for the content information, we developed a new fondness for our PC. We all spend a significant amount of time on our PCs, probably far more than we want to. Having high quality music content at your fingertips will help get you through the day. The Desktop Amp may be the ticket.

- Kevin Nakano






OPPO BDP-103 Blu-ray Player




Review System

Laptop:Sony - Vaio PCG-K23
Desktop:Sony - Vaio VGC-RB34B
Headphone #1: AGK K701
Headphone #2: Sennheiser - HD 600
Earphones: SHURE -
E500PTH


Review - At a glance
Headroom - Desktop Amp Headphone Amplifier

Features:

  • Dual headphone jacks (1/8" & 1/4")
  • 2 Independent sets of RCA-plug analog Inputs
  • Variable RCA-plug Output
  • USB Input
  • Toslink Optical Input
  • Coaxial Digital Input
  • Brightness Filter switch
  • Crossfeed switch
  • Gain switch
  • Rear Output switch
  • Source Selector switch (Analog/Digital)
  • Direct Input Selector switch (Optical/Coaxial/USB)
  • Volume control
  • Power indicator

    Desktop Amp Manual: PDF File

    Company Information
    HeadRoom Corporation
    2020 Gilkerson Drive
    Bozeman, MT 59715
    Toll Free: 800-828-8184
    Phone: 406-587-9466
    Fax: 406-587-9484
    Website: www.headphone.com

    Source: Manufacturer Supplied
    MSRP: $599 (Base Model) with many options available
    Size: 6 ¼” x 6 ¼” x 3 1/3” (LxWxH)
    Weight: 1.8 pounds
    Warranty: 2 years with 30-day guarantee

  • Any comments or questions regarding the LAAF Web Site should be forwarded to webmaster@laaudiofile.com

    Copyright © 1985-2007 L.A. Audio File.