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For this installment of Super Budget components, we’re going to go a bit more upscale and downscale. And then, for balance, I’ll discuss a third component that delivers some serious amplifier power for under $500. So, hold on to your hats, here we go…

NuPrime BTR-HD Bluetooth adapter

$89

Let’s face it. Bluetooth is ubiquitous. I know, it’s not as good as Wi-Fi or an Ethernet connection, but think of it as FM radio (13kHz upper limit) or an analogue audio cassette. It’s good enough to get most of the music.

An audio system without the ability to utilize Bluetooth as an input source is so 1990s. Being able to connect to a system via Bluetooth makes any visitor’s music available. That’s cool. Another use I’ve occasionally found myself needing is wanting to listen to an Internet radio feed not supported by Roon. Connecting my phone via Bluetooth lets me hear music that I couldn’t get easily otherwise. The NuPrime BTR-HD lets you add Bluetooth to any DAC or receiver that has an HDMI, Toslink, or coaxial S/PDIF input. It supports Qualcomm aptX HD, which is one of the highest resolution Bluetooth codes currently available. I connected the BTR-HD via the HDMI/I²S connection to my Gustard A26 DAC with the HDMI cable that came with the unit.

How does it sound? Better than you might expect. Using my iPhone 13 mini I was able to connect to the BTR-HD on the first attempt. I was impressed by the sound quality from a Qobuz file of “People get Ready” by the Chamber Brothers, which had excellent lateral imaging and focus. On minimalist tracks, such as John Zorn’s “Ballade #2”, the sound was more than listenable, it was involving. Only on difficult, densely mixed material was I aware of what I was missing. It was simply harder to listen to the subtle details buried in the mix on material I was familiar with.

If you want to add Bluetooth capabilities to your current rig, the NuPrime BTR-HD delivers a very usable solution. And you could even carry it with you and plug it into your friends’ DACs when you visit them so you can share your music on any system with a digital input. Sure beats the old days of carrying a box of CDs everywhere…

Audiomis MC5 loudspeaker

$1279/pair

When I unpacked the Audiomis MC5 loudspeaker, my first thoughts were, “Oh boy, just what the world needs, another small, rectangular, wood-veneered, two-way with a slotted port loudspeaker! I’ve never seen that before.” Yes, my days of jumping up and down whenever a new box arrives are long gone.

I’ve probably heard more two-way monitors than any other kind of loudspeaker. Most underwhelm. Either they’re too clean and lean, or the designer tried too hard to add weight and impact, which too often translates into excess midbass energy. Arriving at that Goldilocks middle ground eludes most two-ways. Given my usual cynical state, my initial impressions of the Audiomis MC5 did not make me eager to set them up and give them a listen. But duty called.

Finished in a soft satin walnut wood veneer (zebrawood is also available), the MC5 loudspeakers are not unattractive. The speaker grills are decidedly old-school—black fabric stretched over a 3/8”-thick back frame attached via pressure-fit attachments at the four corners of the front panel. Magnetic fasteners would have been my preference.

My current desktop reference loudspeakers include the Audience 1+1, MoFi SourcePoint 8, and ATC SC-7III. Each excels in different parameters. The Audience has the best imaging and soundstage reproduction, the SourcePoint has the most seductive harmonic balance, and the ATC is, comparatively, the most linear and dynamic. While the Audiomis MC5 doesn’t best each of these loudspeakers’ most outstanding features, it does manage to split the difference in terms of sonic trade-offs and include 90% of the most positive aspects of each of the other speakers to arrive at an extremely compelling nearfield transducer.

For me, the most attractive sonic aspect of the Audiomis MC5 is its combination of low-fatigue sound with high resolution. I can listen, nearfield, for most of a working day without needing to turn the MC5s down or off. Yes, the midbass is a trifle warm, but judicious placement can reduce that. While there are plenty of fine two-way loudspeakers similarly priced to the MC5, if musicality is high on your “must-have” list for transducers, these two-ways could very easily find a way into your system.

NuPrime STA-100

$499

Small But Mighty would be a good way to describe the STA-100 basic stereo power amplifier. The STA-100’s chassis measures approximately 6 ½” by 4” by 1 7/8”. It’s all black, with a beveled front panel and vents on the sides. Rated at 100Wpc into 8 ohms and 150Wpc into 4, the STA-100 has three different gain settings: 15, 20, or 30 dB. The power supply uses something that NuPrime calls an “adaptive voltage switching power supply”, wherein the amplifier uses its output signal to feed back to the power supply’s servo stage which changes the output voltage to the power stage. NuPrime claims this design “resulted in more details at low music level and explosive power at high voltages”.  And while the owner’s manual does supply a block diagram of the STA-100’s circuit topology and basic specifications, it does not show any measurements showing how this new power supply design compares with a more conventional one.

Most class-D power amplifiers use one of several manufacturers’ class-D amp modules. Most of the manufacturers trumpet the benefits of the third-party DAC module they employ. NuPrime uses their own proprietary class-D module. They call theirs the NPX-280AS, which they describe as a “550 – 600kHz high frequency class-D power stage.” You can, if you want, purchase the power stage NPX-280AS module separately ($269 MSRP) from NuPrime’s sub-brand website and, if you have the DIY skills, place it into the chassis of your choice*. On the site, you will see different power output specifications due to using 220 AC rather than 110 – 120 AC. If you require more than two channels, you can buy as many modules as you need, put them into the chassis of your choice, wire them up, and go.

Since my two primary systems need a power amplifier with balanced XLR inputs and the STA-100 has only single-ended RCA ones, I assembled a simple impromptu stereo system using the Astell and Kern 3000T portable audio player as my source and my pair of Sound Artist LS3/5A loudspeakers connected via a 3ft-run of ribbon-design speaker cable.

There has long been a debate within audiophile circles as to whether an amplifier has an intrinsic “sound” or its sound is a product of its combination with a transducer and that transducer’s impedance and sensitivity. Different amplifier designs have varying abilities to drive loudspeakers. Some amplifiers will drive anything, but they are traditionally big, heavy, and inefficient. And while some loudspeakers, usually those of equally prodigious size, require such an amplifier, far more loudspeakers can form a happy union with a 100Wpc into 8-ohm class-D amplifier like the STA-100.

I decided to see how loud the LS3/5A loudspeakers would play hooked up to the STA-100. I put in my strongest earplugs (29 dB), set up my iPhone with an SPL meter app one meter away from the left speaker, put on a raucous track and turned it up slowly. At 101 dB, the right channel of the STA-100 went dead. I noticed that the little red fault light located above the blue ON light had come on. I turned off the STA-100, counted to ten, and turned it on again. The fault light did not come back on and both channels proceeded to work properly. So, I guess the STA-100 protection circuits work. I don’t recommend doing this with whatever gear you’ve got. Your amp’s protection circuit might not be as effective, or you could fry a tweeter.

Sonically, the STA-100 is your classic, squeaky clean, quiet as a dead mouse, neutral-sounding power amplifier. Listening through my LS3/5a speakers to the instrumental “The Butcher’s Dog” from Charles Sawtelle’s album From Rancho DeVille, I was impressed by the clarity and precise instrument placement within the soundstage. Even the low-level feedback howl during the tune’s opening notes came through clearly.

I can see the STA-100 finding a place in many high-performance desktop nearfield installations. Combined with a good DAC/preamplifier and loudspeakers that are at least 85 dB sensitivity at one meter, you have the basics of a fine stereo system.

* https://nuprime-x.com/wp-content/uploads/2024/05/NPX-280ASP-installation-diagram.pdf