Generating 120Wpc and weighing just under 10.5 pounds, the STA-9 uses a Class A input circuit with a Class D output circuit. NuPrime’s website says it “is designed with enhanced even-order harmonic circuitry that mimics the most attractive features of tube-amp sound without incurring tubes’ drawbacks and limitations.” It’s easily bridgeable into 290Wpc monoblocks, and its 47k ohm input impedance should work with virtually any preamplifier. In monoblock mode, the STA-9 produced powerful bass, even with the small KEF speakers.
Odyssey Khartago Stereo and Mono
$995 and $1975/pr.
Although the 130Wpc Odyssey Khartago solid-state stereo amp has been around for better than a decade, it was new to JV until amp-connoisseur Alon Wolf (of Magico) told him he used it in his shop and it was excellent. Wolf was right. Although the Khartago doesn’t have all the articulation and transparency of the standard-setting Soulution 711 stereo amplifier, it has a surprisingly similar balance, no discernible grain, high resolution, and a deep, wide soundstage. Positively, the best budget amp JV has heard, not counting the Odyssey Khartago monoblocks, which have the same power rating as the Khartago but a stiffer power supply and wider bandwidth, giving them the same basic sound as the two-channel unit with slightly more resolution, dynamic oomph, top-end air, and channel separation. Like the Khartago stereo, this is a budget monoblock for the connoisseur.
Rotel RB-1552 MkII
The RB-1552 MkII is a 120Wpc Class AB stereo power amplifier with the holistic design and careful parts-selection of Rotel’s best amps. The unit is essentially a dual-mono design and accepts both single-ended and balanced connections (the balanced sound way better). For those whose speakers require more oomph, such as Maggie owners, Rotel makes a more powerful ($600 more expensive) 200Wpc version, the RB-1582 MkII. Modestly priced products may not be able to produce the “absolute sound,” but the best of them can fully deliver the heart of the high end. Rotel’s RB-1552 MkII falls decisively into this category, delivering robust dynamics, a broad soundstage, well-placed images, rock-solid bass, infectious timing, and tonal characteristics that sound “right.”
Optoma NuForce STA200
Basic solid-state power amplifiers are not, due to their essential nature (boxes with parts inside), sexy objects that inspire a lot of audiophile lust. The STA200 will never be accused of looking sexy or especially stylish, unless you’re into stark minimalism. But if sound quality and solid-state reliability are your primary purchasing criteria, the STA200 should be on your radar. You may not be blown away by the ST200’s looks, but its sound turns it into one sexy beast.
Coincident Speaker Technology Dynamo 34SE MKII
The swanky Dynamo isn’t your typical 8Wpc single-ended triode (SET) design. There is no 300B in sight. A 6SL7 dual-triode drives a triode-connected EL34 output stage. There is no global feedback, and the power supply is tube rectified. The 5U4G rectifier arc’d briefly on DO’s sample when the amplifier was powered up. Coincident considers this to be a normal event, but any arc’ing is cause for concern when it comes to the rectifier’s lifetime. The input signal is routed through a 100k ohm pot allowing a direct connection to an external line-level source. Expect a sweet midrange, an exceptionally dimensional soundstage, and a dynamic presentation belying the amp’s miniscule power rating—at least when driving a high-sensitivity loudspeaker. Harmonic textures aren’t overly liquid, implying decent-bandwidth output transformers. Treble textures can be improved via judicious tube-rolling. Here is an amp that shouldn’t be defined on the basis of its cost. It captures much of the magic of SETs at an entry-level price. Because of its high source impedance the Dynamo may not always yield the most accurate tonal balance, but the crux of the matter is foot-tapping musical bliss.
In 2014, NuForce’s co-founder Jason Lim, with backing from the OEM factory, bought the assets of NuForce’s high-end division, obtained the rights to NuForce technologies, and formed NuPrime Audio. In essence NuPrime is NuForce, built in the same factory, but with its focus now strictly on high-performance home-audio products. The NuPrime ST-10 amplifier is what NuPrime calls “near reference class.” Why only “near” reference? As far as reviewer SS can tell it’s because this stereo amplifier only puts out 150 watts per side into an eight-ohm load. The ST-10 is a very quiet, extremely low-noise power amplifier that, as long as it isn’t pushed into clipping, sounds exceedingly neutral and uncolored. SS tried the ST-10 with a variety of speakers from the fairly inefficient 84dB Aerial Acoustics Model 5B to the 95dB-sensitivity Audience 1+1, as well as the ATC SC7 II, Dunlavy SC-1/AV, and Mirage OM3. In every case the amplifier did a superb job of driving the speakers with authority and control.
Audio by Van Alstine Ultravalve
According to Frank Van Alstine, the Ultravalve’s lineage is traceable to the Dynaco Stereo 70, which he denotes as its “great-grandmother.” Although not as romantic-sounding as the original, it is far better focused, and in general sounds like a higher-resolution device. It handles bass lines with superb control and good impact and is capable of dishing out plenty of boogie factor. Its ability to retrieve microdynamic nuances allows for the full scope of the music’s dynamic intensity and interaction between musicians to shine right through.
Alchemy by Elac DPA-1/DPA-1M
The DPA-1 is a stereo switching amplifier capable of 125Wpc into 8 ohms and 200Wpc into 4 ohms. The front panel offers more features than traditional power amplifiers, including selectable gain (a +6dB button), clipping indicators, a mute button, and soft-start warm-up. Both balanced and unbalanced inputs are provided. The DPA-1M is a monaural version of the same amplifier, delivering 325W into 8 ohms and 400W into 4 ohms. Both amplifiers feature a Class A input stage and a Class D output stage, based on Bruno Putzeys’ Hypex UcD module. (The DPA-1M monoblock simply bridges two of these modules for greater output power.) Sonically, both amplifiers have a lively, upbeat sound, powerful rhythmic drive, wide dynamic expression, and rock-solid visceral grip in the bottom end. Soundstaging and transparency are also excellent. A great value.