Reference class mono power amplifier
The ST-10M Reference Class Mono Amplifier builds upon NuPrime’s fourth generation (V4) amplifier module from the ST-10 and brings it to the next level. The ST-10 was designed within the space limitation of its chassis and hence had a power system which was capable of providing 150W power output to each of the stereo channels. To really bring out the best of the V4 amplifier module, the ST-10M has a new 300W power supply for its mono channel. The entire design including the chassis has been optimized for the mono configuration, further lowering the cross channel interference.
Other Circuit Enhancements
The original 10A bridge rectifier has been replaced by a 50A Schottky diode, the capacitors upgraded 30,000 micro-Farad, and duly the power transformer is now rated at 300W. Improved circuit layout with careful component selection has allowed the ST-10M to have a lower noise floor than the ST-10.
The NuPrime Sound
The ST-10M sounds more full bodied and rich, conveys greater immediacy and power as compared to the ST-10. The improved power delivery and reduced interference gives the instruments richer overtones and more natural decay. The soundstage is deeper and creates a greater sense of space. Imaging gains more solidity over the ST-10 which already has an impressive placement.
The effects of the improvements could be heard on the following examples. The striking of piano keys demonstrates greater attack and faster transients, with a sound that naturally resonates with the piano body. Brass instruments sounds glorious, characterful and carries a natural sheen but not overly bright. Female vocals and high frequencies retains the signature of the ST-10 but is smoother on the ST-10M. In an ensemble, the tonality gains an extra notch of richness which makes the overall presentation more natural.
With the ST-10M, every aspect of the ST-10 sound has been improved upon, which makes it truly a reference grade amplifier!
- RCA: Un-Balanced input x 1
- XLR: Balanced input x 1
- Speaker Out x 1
- Power Output (rated): 230W @ 8 Ohms, 320W @ 4 Ohms
- Power Output (peak): 270W @ 8 Ohms, 375W @ 4 Ohms
- Gain: x 28
- Input Impedance: 47k Ohms
- Sensitivity: 1.5Vrms to rated power
- Total Harmonic Distortion (THD): 0.01%
- Signal to Noise Ratio (SNR): 91dB @ 10W
- Frequency Response: 0Hz to 50kHz (-3dB)
- Standby Power Consumption: 0.9W at 115V outlet, 1.7W at 230V outlet
- Idle Power Consumption: 14W at 115V outlet, 14.8W at 230V outlet
- Worldwide AC voltage: (115 VAC / 230 VAC) with Voltage Select Switch
- AC Fuse: Slow-blow, 5A, 250VAC
- Dimension: 59 mm H x 215.4 mm W x 394 mm D
- Weight: 6 kg
- Color: Black or Silver
ST-10M is a phase inverting amp. If you are certain that the +/- (usually the red/white connectors) phase of your inputs are non inverting, then you should reverse the +/- inputs for each channel on ST-10M. All other NuPrime amps were designed as non-inverting amp. If you have no idea what this is all about, don’t bother with making any adjustment.
There is no 12V trigger for ST-10M.
Traditionally I have always stuck to Class A or Class A/B amplifiers. I decided to try out a few Class D amplifiers for my 2 channel listening. I typically prefer a clean, detailed, neutral sound. I like to hear the music exactly the way it was recorded, don't we all? The problem I found with the Class D amps was that the sound was too clean, bright, analytical, edgy. In essence, very clinical which meant very boring. My last few attempts at Class D amplification had buyer remorse set in quickly. I was ready to throw in the towel for Class D amps. I was wanting to try some new DAC's so I purchased the NuPrime DAC-9 from Summit Hifi. I was really impressed with the build quality and sound signature from this DAC so I purchased the NuPrime DAC-10 as well. The build quality and sound bar was raised once again. Now that NuPrime had me convinced that they were serious contenders, I decided to give their Class D amps a chance. I purchased the NuPrime ST-10M monoblocks from Summit Hifi and again, build quality is top notch. The ST-10M's and my DAC-10 are a perfect match and the smaller form factor look is stunning, very classy. So looks aside, how do the ST-10M's sound. In a word, amazing. Everything that I disliked about my previous Class D amp's quickly disappeared with these amps. They were not thin, dry, edgy and clinical like the others. The bass was deep, tight, and very controlled while the treble presented as airy, crisp and clean, not being edgy or overly bright like I was expecting. What floored me the most though was the midrange. My go-to tracks for vocal testing are Kirsti Huke's rendition of Wish You Were Here and Siri Gjaere's Loveless Cafe. Kirsti and Siri's vocals through the ST-10M's gave me chills up my spine, the best I have heard from any amplifier to date. Imaging, depth, and dimensionality, were fantastic. I am sold on the ST-10M's and am eager to start listening to my music all over again. As always, Aamir from Summit Hifi was a big help!
I started my search looking for the best of Class D amplifiers. NuPrime was one product that came up through my search, and after more research on all of their products as a whole, I decided that the ST-10M would be worth taking a look at. There are some glowing reviews on the web about their ST-10 and Evolution One amps, which was nice to see, but a lot of times these reviews need to be taken with a grain of salt (too much creative writing). During my research on NuPrime, the one factor that kept coming up was performance value, no need to spend big bucks for great performance. I contacted Aamir with Summit HiFi to discuss the ST-10M's and his 45 day in home trial period. Aamir was very helpful with any questions I had, and assured me if I wasn't satisfied with the product, I would receive a full refund during the trial period - so it became a no brainer, lets try them out! A week later the amps arrived, they have been burning in for three weeks now. They sounded pretty impressive right out of the box, but have improved greatly over the last 3 weeks. It would be a huge understatement to say that I'm very impressed with their performance. The following are my observations on sound quality in no particular order: Large holographic soundstage, 3D imaging, completely black background, very neutral and highly resolving, tight defined bass, superb mid-range (vocals are awesome), rich tone, smooth and dynamic. Excellent performance from top to bottom, very musical and engaging (toe tapping goodness!) I've been in this hobby for approx. 30 years, and at no time have I come across the price / performance value that NuPrime offers, it really is unbelievable. These amps are the real deal, and I will be keeping them.