A class-D amp product is consisted of three main components:
Preamp Stage, Class D Stage, Power Supply (note that this Preamp Stage is not the volume control preamp, but an integral front-end of the Class D amp design)
Preamp Stage design is made of
(A) - Op Amp or discrete transistors with two difference NuPrime designs:
(B) - ULCAM (Ultra Linear Class A Module) or
(C) - SECAM (Single Ended Class A Module)
Practically all the amp products on the market use Op Amp for preamp stage. Only a few very high end products use discrete transistors design. Discrete transistors design is costly and challenging to accomplish.
Class D power stage design can be Half Bridge (H) or Full Bridge (F).
Power supply can be Switching (S) or Linear (L).
Below is an illustration of how we created the unique sonic characteristic for each product:
IDA-16 = A+H+S (Op Amp + Half Bridge + Switching) for clean, fast, and powerful sound
ST-10 = A+F+L for clean, fast, smooth and refined sound
IDA-8 = B+H+L for a little more warmth and fast
STA-9 = C+H+L for tube-like sound, warmth, and fast
K-38 = C+B+H+S for the best sonic characteristic suitable for watching movies and listening to music.
There are more combinations that we can do here, such as C+H+S or C+B+F+L or C+B+F+S.
So let’s spend a moment discussing an amp’s sonic characteristics. Let’s begin by admitting that there’s no such thing as a perfect-sounding amp. Further, some characteristics are poles apart from others. For example, a warm-sounding amp produces a fair amount of even-order harmonics. And it certainly won't be as neutral-sounding as an amp that produces none. A recording engineer might like to employ both styles of amplification – a super-clean amp as his reference and a warmer amp to help shape the end-product. In the listening is the MCH-K38 better than Ref 20? Not at all! However, if you watch a lot of movies and enjoy to a wide variety of musical styles, you might prefer MCH-K38. If your thing is classical music in its entire vast and dramatic splendor, you will likely go for Ref 20 or ST-10. Conversely, if vocals are your passion, you will likely prefer the MCH-K38 or STA-9.
In conclusion, we advice customers to make their selection based on sonic preference and usage scenario. In particular, higher price model (from NuPrime's own selections or from competitors) does not necessary mean that it is better.
(Related article: Amplifier Design & NuPrime's Advantages)