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Rogers High Fidelity 65V-1 Integrated Amplifier

Rogers High Fidelity 65V-1 Integrated Amplifier

Roger Gibboni, the founder of Rogers High Fidelity, seems to be having way too much fun these days. During a conversation at the recent Rocky Mountain Audio Fest (RMAF) his passion for audio design came across loud and clear. He brings with him an extensive background in aerospace engineering, which is reflected in how his products are designed and manufactured.  The 65V-1 is a perfect example. Although intended as an entry-level offering, it is definitely not a watered-down version of one of Rogers’ big push-pull amps. In fact, it’s something totally different—a single-ended design using one EL34 power pentode per channel, though upon request the amp can be shipped with a KT88 beam power tube.

The design was driven by the challenge of arriving at a final product that sounded as good as a higher-priced Rogers amp, but at a price a young millennial buyer would consider attractive. Gibboni frames it rather delicately by pointing out that the demographic of well-heeled baby boomers is aging out—a trend I observed firsthand at RMAF, where a large fraction of the traffic was gray and bald. It stands to reason that if high end is to survive, new converts are desperately needed. According to Roger, market research indicates that to attract millennials, a product needs to not only compete on the basis of price but also be technically cool. I think that providing iOS app control of a single-ended tube amplifier qualifies as such. An iPad app is freely available from the Apple App Store that allows the user to control volume and operating mode (ultralinear or triode) and to change inputs remotely. Power output level is also on display. Communication is via Bluetooth, which explains the antenna connection on the back panel. Of course, full manual functionality is also available on the front panel.

Measurement is a key element in the Rogers High Fidelity design and manufacturing process. Each piece of gear is burned in for 100 hours prior to shipment and then undergoes a battery of tests. I don’t recall, in my entire audio reviewing career, ever receiving a product accompanied by a comprehensive Audio Precision test report. But that is the level of rigor that Rogers undertakes in its production, and takes pride in the fact that its manufacturing process achieves greater than a 99.8% first-pass yield for acceptance testing after build completion.

Rogers High Fidelity 65V-1 Integrated Amplifier

Perusing the test report, you will find a plot of power versus total harmonic distortion (THD). The number that jumped out at me was a power output of 10Wpc into an 8-ohm load at about 2% THD in ultralinear mode. The plate dissipation of an EL34 is 25 watts, so if it is biased hot you could eke out 12 watts of continuous power from a single EL34, though most designers would opt for no more than 10 watts. Curiously, that type of spec is nowhere to be found in the online promotional material or even in the owner’s manual—one of the main reasons being that Rogers is a firm believer in peak rather than continuous power. According to Gibboni, the ultimate goal is peak power performance, which is seen to be a major factor in making amps sound musical.

I’m sympathetic to the notion of peak or music power, even though the specification has had a checkered history. (It was used in the 60s and 70s to inflate an amplifier’s power rating, before the U.S. government finally stepped in around 1974 to mandate continuous power ratings.) The main point is that music is not continuous by nature, and providing that a tone burst test is sufficiently long in duration (say 200 to 300 milliseconds, to overlap the attack and decay portions of a real-world transient), then such a test would more accurately predict an amp’s performance with music program material. However, for many high-end power amps with beefy power supplies this distinction is moot, as they deliver the same power level under any drive signal condition, either momentarily with a burst tone or continuously, and can be said to have no dynamic headroom. On the other hand, amps with a soft power supply can deliver significantly more power momentarily than they can continuously. In peak power, the 65V-1 is capable of being driven toward clipping while delivering on the order of 25Wpc at 10% THD. Please don’t roll eyes at 10% THD, as that’s the norm for any good single-ended power amp at maximum output. And you shouldn’t confuse even-order single-ended distortion with the odd-order distortion push-pull amps dish out. The former is consonant with music, while the latter is irritating to the ear even in minute quantities. Which would you rather listen to: 10% even-order or 1% odd-order distortion? For me this is a no-brainer. I’ll opt for tube lushness over tube brightness any day.

The audio circuit is quite simple and consists of an EF86 small-signal pentode directly driving an EL34 or KT88 output tube—your choice. Cathode bias is used, which makes changing power tubes rather simple. A tad of feedback (2dB) is employed to flatten the frequency extremes. The EF86 was introduced in the late 1950s specifically for audio applications. It features huge gain (more than a 12AX7) and has found quite a following in guitar-amp applications, with aficionados raving about its sweet textures and full-bodied, caramel-colored tonality. I suspect that it is musical instrument usage that has kept this tube in production in Russia and by JJ Electronic. The tube is notorious for being microphonic, and Rogers takes care to test and select primo samples from new JJ Electronic production.

 

One puzzling design aspect is the insertion of a high-pass filter at the input to intentionally roll-off bass frequencies below 100Hz. Bass response is already off 6dB at 30Hz, and this is clearly audible as a loss of bass weight, not only on organ sustains but also on upright bass. The intent was to provide the user with a rumble filter, but the puzzling thing is that there is no way to bypass the roll-off when rumble isn’t an issue. A positive consequence of the filter is reduced output-transformer saturation due to a heavy bass signal.

The 65V-1’s first task was to drive the Watkins Generation Four loudspeaker, which is capable of exceptional imaging, and pricewise is a good match for the Rogers. As fate would have it, I started my listening tests with the KT88 beam power tube. In hindsight, it became obvious that this was not the best choice. I am not at all suggesting that the Russian Genalex Gold Lion is a bad-sounding tube; it’s just that in this context it didn’t do the 65V-1 any favors. The overall sound took on a distinctly bland character. With the amp lacking a strong sonic personality and being way too polite dynamically, the Gen Four speaker became a mere shadow of itself. From a design standpoint, it’s likely that the 65V-1’s bias resistor is optimized for an EL34. A KT88 needs to draw a bit more bias current—that is, run hotter—to sound its best. It didn’t take me long to substitute the stock Mullard reissue EL34. To say that I was surprised by the resultant transformation would be an understatement. Power tube differences can normally be measured in inches; in this case it was a matter of miles. The Gen Fours took off with convincing microdynamic expressiveness, much better color saturation, and sufficient punch, especially in ultralinear mode, making it sound like it was driven by a much more powerful amp. Watkins recommends a minimum amplifier power of 40Wpc, so in all fairness, the 65V-1 should not be considered an ideal choice for this application.

It was time to make life easier for the Rogers by giving it a chance to drive a much higher-sensitivity speaker load. The OB3 open-baffle DIY speaker (94dB) was rotated into the reference system for that reason, and for the fact that it had shown a preference for low-power tube amplification. It was then that I started falling in love with the Rogers. The crux of it was a lush and expansive midrange that I could get lost in when I closed my eyes. I preferred triode mode to UL. Not a big surprise here. With high-sensitivity speakers, it’s all about the quality of the first watt, and at least with this amp a triode watt sounded sweeter and more relaxed. It takes the amp a while to start singing. A slight veiling of the soundstage and defocusing of image outlines disappeared after about 30 minutes. Image outlines fleshed out to almost palpable presence, and it became possible to access the inner recesses of the soundstage. There was an organic wholeness to the stage that gave the impression of continuous width—a far cry from the discontinuous left, right, and centerfill presentation that some amp/speaker combos insist on. Moving my head from left to right in no way disrupted the illusion of “being there.”

Power response was fairly well extended. As a result, perceived transient speed was quite decent without overly liquid textures. Tube liquidity and richness are good things, but at a certain point can turn sonics into a gooey mess that masks low-level detail. To its credit, the Rogers negotiated the richness/detail tipping point quite well. As mentioned earlier, the significant fly in the ointment was the bass range, which lacked sufficient heft. The amp’s source impedance is 9.5 ohms, which gives it a damping factor of about one into an 8-ohm load, though I don’t think that this is necessarily the reason for the loss of bass line tightness. (The Coincident Dynamo 34SE Mk. II, which sports an almost identical source impedance, does much better in this regard.)

This dichotomy in sonic character was clearly evident on the Charlie Hayden/Jim Hall duet concert album recorded at the 1990 Montreal International Jazz Festival. Hall’s guitar was boldly and vividly etched in space within the confines of a lovely acoustic. On the other hand, Hayden’s doublebass lacked authority and precision. To my mind, the reason to buy the 65V-1 is its midrange, which towers above the competition at this price point. You really would be hard-pressed to find a more cogent and emotion-packed midrange. And that’s what keeps me coming back to this amp. These are basically the same reasons I still own and enjoy a pair of the classic Quad 57 ESLs. On balance, indulge yourself. This is an entertaining amp that deserves a serious audition.

Specs & Pricing

Frequency response:  20Hz–20kHz +/-0.1dB
Power output: 25Wpc at clipping at 10% THD
Inputs: Four RCA
Features: Headphone jack; Bluetooth communication with iPad
Weight: 24 lbs.
Dimensions: 17″ x 7.5″ x 12″
Price: $4000

ROGERS HIGH FIDELITY
info@rogershighfidelity.com
rogershighfidelity.com

Associated Equipment
Speakers: Watkins Stereo Generation Four, OB3 open baffle (DIY)
Analog source: Kuzma Reference turntable and Stogi Reference 313 VTA tonearm, Clearaudio da Vinci V2 MC
Digital sources: MacBook Pro laptop running Amarra V3.04 software, DiDit 221se DAC, ModWright modified Sony XA-5400ES SACD player
Cables: FMS Nexus-2, Wire World, and Kimber KCAG interconnects, Acoustic Zen Hologram II speaker cable
A/C Power: Monarchy Audio AC-Regenerator, Sound Application power line conditioners

Tags: ROGERS

By Dick Olsher

Although educated as a nuclear engineer at the University of Florida, I spent most of my career, 30 years to be exact, employed as a radiation physicist at the Los Alamos National Laboratory, from which I retired in 2008.

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