The overarching design goal was to create an excellent-sounding, well-built power amp with a useful amount of power. We also use veryhigh-quality parts throughout the Stereo 100, including aluminum/oil Mundorf coupling caps, lots of Vishay and PRP resistors, as well as Cardas hardware. Both of the Stereo 100's high-voltage supplies use large electrolytic capacitors for storage, all of which are bypassed by high-quality film capacitors. "There are five separate power supplies in the Stereo 100all of which utilize pi filtering to reduce ripple, thus providing a very low noise floor. Your readers might know that when you are listening to a power amp, you are effectively listening to the sound of the power supply being modulated by the audio signal. The power supply is one of my favorite design areas, and is truly critical to the audio performance. Output power is 100Wpc in Ultralinear mode and about 60Wpc in Triode. We use custom power and output transformers designed around the Stereo 100 circuit. "The output stage consists of a push-pull pair of Tungsol KT120 output tubes that can be operated in either Ultralinear or Triode mode via a switch on the rear panel. We use the JJ Long plate Euro-spec versions (ECC802S and ECC803S) for all of these small-signal tubes.
#100 rogues driver
The next stage is a 12AX7 voltage amplifier followed by a 12AU7 driver tube. This is an expensive way to couple the balanced signal, but it sounds really good, and has the added benefit that we can connect the RCA inputs through it to achieve much of the same noise-reduction benefits as the balanced inputs. Many companies use a FET or other solid-state device on the input stage, but I prefer the sound (or lack thereof) of a high-quality transformer. We use a very fancy Jensen transformer to get the balanced signal in. "The topology of the Stereo 100 begins with the transformer-coupled input stage. 7, Zu Audio's Soul Supremeas well as the most uncolored and coherent two-way dynamic loudspeaker I've heard, Harbeth's M30.2 ($6495/pair).īut conspicuously missing from my audio menagerie has been a fast, neutral, 100Wpc tube amp to put more pop, fire, and maybe a little glow, into the Harbeth M30.2s.Īfter surveying what's available at working-class prices, I decided to start my auditions with Rogue Audio's all-tube, 100Wpc Stereo 100 amplifier ($3495).Īs I was told by Rogue's founder, president, and chief engineer, Mark O'Brien, I also collected a range of affordable, popular loudspeakers: DeVore Fidelity's Orangutan O/93, Falcon Acoustics' LS3/5a, KEF's LS50, Magnepan's. How else might they imagine the relative merits of the component under consideration? Once I realized this, I began acquiring a range of reference amplifiers, such as the low-power Pass Laboratories XA25 and PrimaLuna ProLogue Premium, the high-power Bel Canto Design e.One REF600M monoblocks, and the single-ended Line Magnetic LM-518 IA. They were stressful and tediousand what if I got them wrong? But I quickly learned: Not only do readers enjoy comparisons, they need them. When I began writing for Stereophile, I dreaded doing comparisons.