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October 2010
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Rogers High Fidelity EHF-100 Integrated Amplifier
Escaping my room to join the performance.
Review By Ron Nagle

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Rogers High Fidelity EHF-100 Integrated Amplifier  Yes, the Rogers name is familiar to all of the older ear oriented audio types I know. However, like a phonebook High-End Audio is populated from cover to cover with people and banners that sound the same. One I can recall famously made speakers of great repute, and that was their claim to fame. But this particular sound alike is in all-manner different, it is in the hardware game. Rogers High Fidelity is a new start up so you might very correctly call it a cottage company. Small now but then consider that is how the whole of the Hi-End began. It is mainly the brainchild of one Roger Gibboni with an able assist from David Gibboni, the VP of Marketing Development. Earlier in the spring of this year, I attended a demo of their first product a very similar looking tube powered amplifier. Mid July, I followed up on an announcement that the company was about to release a new product, it would be Rogers first integrated amplifier. Did I want to get an exclusive report on a brand new audio component, well duh, yea? Moreover, in the bargain I would get a very, very rare first crack at a new amplifier serial numbered 2001. That numerical tag audio pals actually indicates the very first, EHF-100 Integrated Amplifier made by Rogers High Fidelity.


Let me borrow this down under Aussie phrase to start a tour of this story’s subject. The EHF-100 is custom built one at a time to match your system requirements. It comes covered with Satin Black lacquer paint on all surfaces. Silk-screened on top of this are the silver colored Rogers logo, model designation, tube types, dial, and rear panel markings. Basically this amplifier has what I think of as a classic open chassis design. It has a form factor that reminds me of the Audio Research VSI 60 and the Dynaco Stereo 70. The physical dimensions are: Front 17” wide, 14” deep by 8.5” high, weight 50 pounds. The right front face of the chassis has a pair of RCA input jacks and to the left of that is a four-position source selection knob. Dead center is a small D’Arsonval Distortion meter with a dial scale calibrated from zero to one milliampere. To the left side of this is the volume control knob and to the left of that are two lighted rocker switches. The left switch applies Power to the tube heaters and chassis circuits. To the right of that the second rocker switch labeled Operate applies B+ to the KT 88 power pentodes. The EHF-100 is a three-stage Class A push pull amplifier. The manufacturer refers too the EHF-100 as an isolated channels stereo amplifier with 150dB of separation. The following describes just one channel of the EHF-100. The design of the first stage utilizes a hi-gain EF86 Pentode providing 30dB of amplification. The second stage employs a dual triode 12AX7 in a common cathode configuration operating near unity gain as a phase splitter. This stage controls the third and last stage comprising the two KT88 output power pentodes.

No surprise, the rear top deck has three laminated transformers hidden under a slotted ventilated cover. In the center is the amplifier circuit’s power supply transformer, on the left and right sides of that are the stereo channels power transformers. The manufacturer rates the EHF-100 power supply as 500 Watts. Walkabout to the rear of the amplifier and you will see the three pairs of RCA input connections labeled one, two, and three and of course just to the left are four speaker binding posts for the speaker cables. At the right rear is the IEC power cord receptacle containing a 4-Ampere fuse. Just to the right side of that is a screw type fuse receptacle with a one-amp slo-blow fuse for the high voltage power supply. The manufacturer tells me that replacement KT88 tube parameters should be similar in specification even though the EHF-100 has a bias compensation circuit.


Some Extra Ordinary Specifications
The following information is worth highlighting:
One hundred watts per channel RMS, one hundred fifty watts peak power.
Push Pull circuit operating in class A at less than 0.1% distortion.
KT88 B+ plate voltage specified at 575 volts.
Frequency response is 2 Hz up to 100 kHz

The EHF-100 circuits are hard wired from point to point and does not use interstage coupling capacitors or transformers. The manufacturer further states that the circuit components and wiring all meet or exceed military specifications.


The D’Arsonval Meter
The intended purpose of this front panel analog mini meter is unique and requires further explanation. Transcribing directly from the Rogers EHF-100 operations manual: “The Distortion Indication Meter uses a power combiner to sample output power from each channel and combines that to give a relative output power indication. This relative power level indication can be used to set a maximum power output without tube saturation and hence distortion. This operating point is a relative indication and dependent on speakers and music frequency content.”

“The proper way to set the maximum power output without distortion is to play a desired test soundtrack. Increase the gain control until saturation is heard in the speakers. The first indication of this distortion is powerful low frequencies overpowering higher frequencies. At this point the amplifier is saturated and clipping of the sound will begin. Note the relative indication of this point on the distortion indicator and operate the amplifier approximately 20% below this level. This should guarantee distortion free operation for most music.”


The forgoing description now viewed in a different context. Do you recall the heyday of Japanese Hi-Fi Solid State Receivers? Their claim to fame was vanishing levels of music distortion typically on the order of 0.001 percent. In other words, the inference was that their products had no distortion. Certainly, what we see now is a refreshing and honest turnabout, a discussion of distortion from the Rogers people. But then isn’t this application all dependent on individual perception of what you consider too loud or too distorted? Pardon my skepticism concerning Joe Subwoofer and the A/V surround sound scene or the head banging rock concert crowd, I believe they vastly outnumber us. Considering my predilections and my small listening space, I would never normally need to refer to that distortion meter. Still, I very much like the little retro milliamp meter thingie even though any genuine Audiophile should be able to simply use their ears for this purpose.


Installation is very straightforward. First plug in all of the eight tubes, the positions are clearly marked on the top of the chassis. After that, install the four red tube shields. Next, I connected these source components: A Sangean HDT-1 Digital radio tuner and my Marantz SACD/DVD DV8400 CD player then my Cambridge Discmagic CD 1 Transport and separate S700 D/A Converter. Next step connect my Kimber 12TC speaker cables to my Aurum Cantus leisure 2SE speakers. Last step, connect the power cord and actuate the Power switch, wait about 30 seconds and then actuate the second switch labeled, Operate. A note of caution: The EHF-100 runs unusually hot and should be allowed to cool before handling.


First Things First
Follow this suggestion, don’t apply power and go straight to your sweet spot seat. My normal routine doing critical listening, is that no matter what is substituted in my system, be it a speaker or a new set of cables. I wait awhile and let the system interact and settle down. This caveat is even more important when listening to the EHF-100.  From the initial power on you will hear a gradual increase in the control this amplifier exerts on the deep bass frequencies. Early on the very first few recordings I selected had a lot of bass energy, and did dominate the spectral balance. The effect was that the upper midrange and treble seemed disproportionately less prominent. Even now it routinely takes approximately fifteen minutes with my burned in EHF-100 review sample to take final control and balance all the elements of the performance.


Listening Notes
First let me say that the more I sit and listen and have the EHF-100 in my system the more the sound seems to improve. And yes, my pessimistic super hearing Golden Eared friends will tell me that this is a psychoacoustic effect and I am simply acclimating to the sound. Not so! There is much more to be said. My primary listening preference is always the sound of a human voice, it is this I know best. I will use a wonderful Clarity Cable compilation demo disc given to me at the Las Vegas CES, it is this disc that I now refer too.

First up is a really great recording of Peggy Lee singing her signature song, Fever. The very first note is a deep drum whack, following this joined and accompanied by a resonant plucked bass line. This acoustic bass line sets the tempo throughout the piece and supports Peggy’s vocal artistry. The bass reproduction is exactly as it should be warm wooden and organic, nothing added nothing lost. Those very same natural/organic qualities place Peggy Lee about eight feet in front of me, once again alive and breathing.

Another compilation track would be the George Benson rendition of the Beatles song, The Long Winding Road. The thing that sticks out at me is the edges in Georges Bensons voice and the way he over stresses certain syllables. Me thinks he is the polar opposite of Nat King Cole’s golden glissando’s. The point here is that the vocal renditions I am hearing are the truth and nothing but the truth, they are fleshed out with all the rough edges included.

For the classically curious, the next selection must include a full symphonies orchestral performance. Track one on this CD is, Eiji Oue conducting the Minnesota Orchestra’s rendition of Fanfare for the Common Man. The opening notes are the incredibly deep resonating struck sounds of a Kettle Drum followed by a massed brass Fanfare, this brass response will send chills down your spine. The recording venue is clearly a vast space and the volume of the hall reverberation is enwrapping and emotionally involving. This last track is by Supertramp and their performance of the song Take the Long Way Home. With a recording like this that is made up of overlapping studio tracks and injected studio reverberations the EHF-100 is out of its element. Listening to this you won’t key in on anything wrong but then you won’t hear what the EHF-100 does best. Please understand that the selections above are only a portion of my total listening experience.


The essential sound reproduction as heard through this amplifier is very hard to convey. This is because the EHF-100 is a mixture of the characteristics I would normally associate with other designs both tube and solid state. The body of the sound is strikingly similar to many of the lush mid range tube qualities you would associate with a Single Ended Tube amplifier. However the sound does share many of the qualities you would normally attribute to the greater power of a tube based push pull amplifier operating in class A/B. This means that you will not be restricted to a relative handful of highly efficient speakers as you would hen using to a SET amplifier. Transient speed and extension is not as comparable to, let us say a big buck Krell amplifier. And while the Bass does go very deep it is not with the same bass control that you can get with a large solid-state amplifier. For me the allure of this amplifier is a quality I hold above all others. It is the expansive capaciousness of a wide open soundscape. It is this quality that enables me to escape the confines of my room and join the performance. Indeed I have placed my speakers about as far apart as I can and still the sound stage is wide and deep and tangibly filled with music. Add to this dimension the organic even order harmonic quality of tubes and you have a formulary for a reality that can suspend disbelief. This is most certainly a tube loving audiophile’s amplifier.

As always, Semper Hi-Fi


Type: Vacuum tube stereo integrated amplifier
Frequency Response: 2 Hz to 100 kHz (+/- 1.5dB)
Tube Complement: Two EF86, two 12AX7 and four KT88 
Inputs: Four stereo analog
Output: Standard gold-played binding posts
Output Type: Push-Pull, full Class A design
Output Power: 100 Watts (RMS) per channel
Total Harmonic Distortion: < 0.1% at full output
Gain: 30 dB per channel
Input Impedance: 1 Meg Ohm
Output Impedance: 4, 8 or 16 Ohms
Weight: 50 lbs
Price: $3999


Company Information
Rogers High Fidelity
52 Kain Road
Warwick, NY 10990

Voice: (845) 987-7744
E-mail: roger@rogershighfidelity.com
Website: www.rogershighfidelity.com














































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