Primare CD35/I35 Prisma Network/CD Player & Amp Sidebar: Custom Class D

Sidebar: Custom Class D

For some years Primare amplifiers have been equipped with its own brand of analogue Class D amplifier technology called UFPD (Ultra Fast Power Device). Like the Hypex range of Class D modules, UFPD is a very high efficiency, single-ended Class D amplifier that integrates both the switching and low-pass filter stages within a global compensation scheme. This actively adjusts the precise amount of feedback according to signal conditions and typically offers an entirely predictable response and distortion regardless of variations in the speaker load impedance.


Freq. response (note 1kHz-100kHz scale) into no load [black], 8ohm [grey], 4ohm [red], 2ohm [blue] and 1ohm [green] loads

As we've demonstrated in earlier reviews, that's not something we can say of all Class D amps [HFN Aug '18 & HFN Jul '16]. For the evolved UFPD 2 version of this amplifier Primare has further refined the output filter inductor. It has also traded a reduction in amplifier gain for an improvement in the gain bandwidth, pushing any residual speaker-related response variations out to higher frequencies. The inset Graph shows the I35's frequency response into an open circuit [green] and 8, 4, 2 and 1ohm speaker loads where it holds to ±0.1dB up to 20kHz [note the 1kHz-100kHz scale]. PM