|Rogue Audio Eighty-Eight Magnum Stereo Power Amplifier|
|Home Theater Power Amplifiers Stereo Amplifiers|
|Written by Brian Kahn|
|Tuesday, 01 October 2002|
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Rogue Audio is a fairly new company in the world of high-end tube audio gear. Formed in 1994 by Mark O’Brien, who remains involved with the company as its president and head designer, Rogue Audio strives to provide reasonably priced, high-quality tube gear. A review of the Rogue Audio components reveals that the company spends its time and resources on items that will improve sound quality and not on gingerbread that is unlikely to be used often by audio enthusiasts.
The Rogue Audio Eighty-Eight Magnum power amplifier is a good example of Rogue Audio’s efforts to provide high-quality sound, without frills, at a very fair price. The Eighty-Eight Magnum amplifier retails for $1,995, only $400 more than the non-Magnum version. The Rogue products can all be purchased in their regular versions, or for a small increase in price, the Magnum version with upgraded parts reminiscent of a "The Parts Connection" upgrade kit. Rogue Audio states that the Magnum line accounts for the majority of their sales.
It is easy to see why the Magnum line is becoming popular, following Rogue’s philosophy of a lot of bang for the buck. The Magnum series upgrades include upgraded power supply components, capacitors, resistors, binding posts, tube sockets, tubes and wiring. No flashy upgrades, no fancy options that only a few will use, just solid engineering where it counts. While I have not had the opportunity to listen to the non-Magnum version of the Eighty-Eight, reviewing the upgraded parts list alone indicates that it is probably a wise investment.
The Eighty-Eight came well-packed, bolted to a wooden base and the large driver tubes boxed separately to keep everything safe. After I removed the Eighty-Eight from the box, I was able to see the silver faceplate was made of heavy machined aluminum, with a large black circle in the middle. The circle is slightly set back, with a brushed silver power button in the center, a blue power light just above it. This design won’t grab your eye the way the new Krell or the Conrad Johnson 17LS preamplifier will, but it will definitely score much higher on the aesthetic charts than the typical black box audio component. Once I removed the amplifier from the wooden base, I was surprised that the chassis was a bit flexible with the cover removed. The amplifier was stiff enough with the cover attached and I would caution against moving the unit with the cover detached to avoid damaging the chassis with excessive flex.
The cover is made of heavy black steel and is well-perforated to allow fan-assisted tube cooling. I was a bit wary of noise when I saw the fan, but later found it to be very quiet and non-intrusive during listening. The back panel features high-quality binding posts and single-ended inputs, as well as a detachable power cord. There are no provisions for bi-wiring or balanced inputs. The lack of balanced inputs was a conscious choice by Rogue Audio, as the addition of balanced inputs would have added at least two hundred dollars to the price without any sonic benefits. This is in line with the Rogue Audio philosophy of delivering maximum value for money.
The circuit topology of the Eighty-Eight utilizes 12AX7 paraphase input tubes feeding two 12AU7s per channel. The 12AU7 mu-follower drivers feature low distortion and desirable impedance characteristics to drive the two Russian-made Electro Harmonics 6550 output tubes. The Eighty-Eight can be run in Ultralinear mode for 60 watts per channel, or triode for 35 watts per channel. There are user-selectable four and eight ohm output taps. Both the tap selection and the selection between ultralinear and triode modes require removing the cover. These selections can be made with simple re-configurations within a minute or two of removing the cover. There are no other internal adjustments to be made, as the circuit uses a cathode biasing design, eliminating the need for bias adjustments.
I set the Eighty-Eight Magnum power amplifier up in my reference two-channel system. I placed the amplifier down on an amplifier stand, providing a solid surface and plenty of working room. It is important to select a location that provides plenty of ventilation, as the unit uses a fan to keep the tubes from overheating. I removed the top easily enough with a Phillips screwdriver and went to work on the tubes. The only tubes needing installation are the four large output tubes, which were easily installed in a couple of minutes.
The other internal settings, discussed above, are the selectable impedance taps, which permit choice between triode and ultralinear modes. The amplifier ships in the ultralinear mode. To switch modes, the user simply sets four switches to the desired mode. Selecting between the four and eight ohm taps is slightly more complicated, but still easily done in a few minutes. The amplifier comes with the eight ohm wires connected to the inside of the speaker binding post. The four ohm wires are covered with plastic sleeves. To switch between four and eight ohms, simply disconnect one set and connect the other.