Channel Islands Audio D-500 MK II Monoblock Amplifiers

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Audio power amplifiers provide the juice or alternating current for our speakers to move in and out, creating positive and negative pressure (Sound). This electromagnetic induction
relies on the marriage of speaker drivers, cabinets, crossovers, and, of course amplifiers. While various amplifier topologies exist, designing one that accurately portrays music can be a challenge. Channel Islands Audio, has been cooking up high-quality audio designs for over 18 years, and I recently had the opportunity to audition a pair of their 500 watt monoblock amplifiers. The Channel Islands Audio D500 MKII mono block power amplifiers currently in their 2nd iteration have been powering my system for a couple months now.

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The Class D design of this audio amplifier allows it to run very efficiently. In fact, they run cool to the touch. I can recall many class A amplifiers that raised the room temperature by several degrees, add a room full of studio equipment and you get a hot and sweaty audio engineer- no fun.

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Each amplifier and massive power supply is housed in a separate steel frame and aluminium chassis. Don’t think you have room for monoblock amps? With a height of 4 inches and a tidy footprint of just 8.5 wide by 13.5 inches deep, these amps will tuck away more easily than you think. The casework is tight fitting aluminium with non-magnetic steel hardware and an On/Off push button with a blue LED surround.

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Rear XLR or unbalanced RCA inputs, speaker binding posts, trigger, AC

Moving to the business end, the D500 MK II provides XLR or RCA line-level inputs, 5-way speaker binding posts, trigger inputs, and an IEC power inlet. For my listening, I connected to each amplifier via balanced XLR connectors from my monitor controller. I used a pair of 2-way (1st order xover) speakers for listening and a well designed room at a hollywood mastering studio. As far as after market power cables go, we found these amps sounded best/most balanced with the cord supplied (i.e. nothing fancy).

After warm up, we fed a variety of studio quality masters through these monoblock amplifiers. I started with a favorite, Muddy Waters Folk Singer. In this hard panned early stereo recording very distinct tracks of guitar, vocal, bass, and drums can be easily distinguished. A great recording true, but the dynamics of the vocal really stress the ability of amp and speakers to communicate the space (echochamber at chess records) and impact of this album. The CI Audio amps did not let me down. Not only was the control over the music’s dynamic fluctuations handled well, but they did so with ease and lightning fast response. Hearing the space around the music is important for feeling an honest connection to the performance. No where is it so obvious as with Mumtaz Muhal, a stereo recording done in a chapel with three musicians. This recording features Taj Mahal performing songs like Stand By Me with Indian classical instrument accompaniment. The Mohan Vina, a slide-like sitar follows the vocal massaging of Taj Mahal like a second voice gently ascending. The natural space of this recording is preserved and replayed over the CI Audio monoblocks with all the emotional connection and tone intact.

Playing back a 24/96 transfer of Stevie Wonder Songs in the Key of Life showed how these little beasts grip your speakers and provide extended tight bass. Listening to the track I Wish showed off these amps ability to clearly portray all the tracks in this loaded mix. A wide and appropriately deep soundstage was achieved using the D500 MK II amplifiers. Even when the overall sonic energy of a song’s mix was full, these amplifiers reproduced clearly and without any strain. Side Note: I’ve been playing these amps for over 8 hours and they are cool to the touch!

Listening to full orchestral pieces from Beethoven’s 9th symphony truly showed off these mono block amplifiers ability to further handle complex and dense musical passages. The quietest passages arose from a black background and when the double bass stepped in, it did so with stride and control usually unheard  in my small speakers. Through the roll of the timpani and onward, the full orchestra was handled with an even and accurate tone. Localization of instruments was obvious and portrayed the stereo microphone technique clearly.

For a wider variety of instruments and sounds I pulled out Beck’s Sea Change and Tom Wait’s Swordfishtrombones. Reproducing the raspy voice of Waits or the somber melancholy stylings of Beck, The D500’s were true to all the fleshy midrange detail. Moving up the frequency range, even the extended response of cymbals was smooth and never overly bright or etched.

While we did not have other speakers to directly power from the CI Audio amp, we did have several other systems in place for monitoring audio. The Lipinski Sound amps and speakers were compared to the Channel Islands Audio amps and GMA Eos HX speakers. Myself and other engineers concluded that the sound of each system were both resolving and usable. The Channel Islands D500 MK II proved to be a clear musical amplifier with a place in the audiophile as well as professional markets. Happy Listening!

Channel Islands D500 MK II Specs:

Power Output 500 watts @ 8 ohms/800 watts @ 4 ohms Bandwidth 50kHz

Frequency Response10Hz – 20kHz, +0dB/-0.5dB

Damping Factor>1000Input Impedance100k ohms Gain 38db or 32db

Dimensions 8.5″w x 4.0″h x 13.5″d

Weight 28 lbs (each)

Warranty 5 Year Parts & Labor

Associated Equipment: Crane Song Avocet, SADIE, Lipinski Sound, GMA Eos HX

EQ Your World with “Here Active Listening”

Doppler Labs just raised $17 million to produce a wearable bionic hearing device. Here Active Listening is being dubbed the first true “hearable tech.” These are not earbuds for listening to music, but rather a kind of bionic hearing device for engaging with real world sounds around you. By using two ear buds with microphones and internal processing, an individual user can curate his/her own listening experience in various acoustic environments (with the aid of a smartphone app). Noisy environment, bad mix at a live concert- any situation where you are engaging with real-world sounds.

Here, Hans Zimmer (film composer) discusses the future of sound and how wearables may change our perception of sounds around us:

The New Green Mountain Audio Eos HX

Green Mountain Audio Eos HX
photo by Vahan Baladouni

Associated Equipment:

Source: Macbook Pro running Pure Music with a large variety of recordings and resolutions.

Amplifier: Anthem MCA-2 class A/B

Computer interface: CI Audio Transient II USB to S/PDIF converter and VDC-5 MK II (power supply)

DAC: Crane Song Avocet DAC/Monitor controller (Discrete Class A)

Power: Shunyata Hydra 2 x 2 and power cables (various: copperhead, sidewinder VTX, Hydra VTX…)

Cables: Audio Magic Sorcerer speaker cable, Excalibur II interconnect, DH labs D-75 BNC to RCA, & Wireworld starlight USB

Eos HX

When you think of traditional speakers you often expect a wooden box of some type with drivers arranged inside. Not so with Green Mountain Audio’s Eos HX. In fact, no wooden cabinets here, except for the lovely Cocobolo wood that surrounds the tweeter. By taking a closer look it becomes evident that unique materials were used to build this speaker. The handcrafted Eos HX from Colorado Springs, CO combines artisanal workmanship with engineering refinement.

The Eos HX Tweeter surrounded by Cocobolo wood
photo from Green Mountain Audio

This HiFi meets steam punk design is the brain child of designer Roy Johnson. Mr. Johnson has spent years researching and developing a full range of speakers, and the Eos HX sits at the top of his 2-way designs. Never quite satisfied, the Eos has seen three iterations: the Eos, the Eos HD, and the latest being the HX. 

These speakers are  full of innovation. Starting with the Q-stone cabinet material, these monitors have a unique ability to be shaped in acoustically appropriate ways while also maintaining a low self resonance. The curved shape around mid/woofer allows for the fullest dispersion of sound, and the adjustable tweeter employs wool felt discs to eliminate early cabinet reflections. Without metallic resonances, the lightweight soft dome tweeter from Seas extends beyond 30Khz. The twin ports for the woofer have  been specially designed to more efficiently handle bass pressure. What you end up with is a truly tuneful bass response with an excellent percussive attack.

The heart of the Eos HX is found in its crossover circuit. Through much refinement, Roy Johnson has arrived on a crossover design (1st order) that works at achieving time-coherence  across the audible frequency range. Further sonic enhancements include Marigo internal wiring and Audio Magic nano stream process for the entire crossover circuit (including internal wire and binding posts). All these combined refinements further the speaker’s ability to reproduce nuances in the music.

The Eos HX rear with Vampire Wire binding posts
photo by Vahan Baladouni

Spending some quality time with the Eos HX proved to be very enlightening. While the bass extension rolls off around 50 hz, these 2 way compact speakers (6 inch mid/woofer and fabric dome tweeter) produce an even and smooth marriage between tweeter and woofer. The dual ported Eos HX maintain an accurate and satisfying extension of low-end, especially in smaller listening rooms. Recordings like Count Basie to more modern pop styles of Beach House were reproduced with greater resolution than I had previously heard. Even micro details were more readily heard, but never in an overhyped way. With such a natural sound reproduction of voice and instruments, I found myself hearing much deeper into recordings. The stereo image is quite amazing for a monitor of this size.

I cannot emphasize enough the emotional quality these speakers reproduce. All the attitude and inflection of singers were heard with an obvious transparency.  listening to multiple voices proved to be very revealing, localization and distinctions from singer to singer became more obvious. When I turned my attention to percussion instruments like cymbals, the articulation of attack was easy to hear and subtle differences between strikes were apparent. Cymbals have never sounded so real and fully textured. Whatever the instrument, The Eos HX have an uncanny ability to reproduce it without adding to or smearing the sound. Most importantly, these speakers produced a highly musical and involving listening experience. Without reservation, I highly recommend auditioning the Eos HX.

Pure oxygen free copper directly gold-plated binding posts
Photo from Green Mountain Audio

Further information on Green Mountain Audio can be found here.

Happy Listening!

Is Your Album Transparent?

Your favorite music served up on various formats

Hi-resolution downloads have been on the audiophile scene for a while now with mixed user feedback. Companies like iTrax and HD Tracks have provided what they claim are high-resolution audio files for customers to purchase and download.  HD Tracks has been accused of selling upsampled digital audio masters instead of truly transferring the audio in real time from the master tapes. iTrax, on the other hand is adamant about their HD music downloads being authentic.  iTrax focuses on recent recordings made using new HD recording technology (i.e. 24 bit 96Khz Analog to digital converters used to convert the microphone preamp).

While HD Tracks has investigated the dubious upsampled audio, it is hard to keep track of how different mastering houses/record labels actually deal with the audio in their studios.  HD Tracks does not inform the customer about how or where the audio is from (save for one release so far). iTrax, for the moment, seems to be much more transparent about how their audio is dealt with. Older analog master tapes can be transferred to high-resolution digital audio files, it is up to us to demand that the process used is fully disclosed.

I notice a lot of discussion (web forums) about the HD Tracks releases and whether or not the files are real or merely upsampled. As an engineer, I can appreciate the scrutiny.  What I find curious is that these forum discussions seem to be concentrating on the science of the data. Sure, I care about that, but let’s actually use our ears and listen.  Did they do a good mastering job?  Was the music uncompressed but brittle?  Well, I personally am looking for a great rendering of a master recording.  Just because it is uncompressed does not mean it is better. While compression/EQ can be done too extremely (modern pop recordings), it can also be ignored to the point of being just as sonically tasteless.

Not only do we (the customer) not know who is engineering all these high definition reissues, we are also unaware if mastering took place or what exactly is going on. We the consumer must also realize that record label executives, distributors (like HD Tracks, Mobile Fidelity, Analogue Productions, iTrax), request different mastering techniques. Bottom line: different reissue labels will approach mastering differently. It is up to us to educate ourselves, and support those reissue labels who are sonically transparent about their mastering methods.

Audiophile Album Reissues

This brings me to another point about audiophile reissues. Often times I am disappointed to hear that audiophile labels don’t use EQ, compression, or anything.  Do they use a mastering engineer?  The only recordings I find that need little if no mastering are very well recorded orchestral music and small jazz ensembles.

It is unfortunate that the loudness wars of the 90’s have misinformed people about what mastering is all about. Through my investigation into audiophile music releases I came up with some thoughts:

  • The Vinyl record has certainly made a comeback – as it should.  Aside from having the ability to apply EQ for vinyl mastering, compression is dealt with quite differently. The physical limitations of the vinyl LP do not allow for too much compression, or the grooves will overlap when the cutting is taking place. Even more, vinyl demands care and attention when cutting is done.
  • This is not to say that vinyl records cannot be mastered poorly, those records certainly exist. It is just that in recent years, I have found a good number LP reissues that tastefully render the sonic qualities of a recording.

Know your record label

Great recordings in hi resolution exist, it is just important to request that these labels disclose the techniques and tools used.

Now go listen to an album! Repeat…

On the turntable:  Ella and Louis (mono45 RPM), Echospace Detroit