Pre/Power Amplifiers

Rather than use its own UFPD2 (Ultra Fast Power Device) Class D modules that we saw in Primare's A35.2 stereo amp [HFN Dec '19], the A35.8 utilises eight Hypex NCORE NC500 modules, mounted as pairs on custom heatsinking, to form four discrete stereo banks. The single-ended Hypex modules are used to impressive effect in many products, including Primare's own I15 [HFN Oct '18]. A key feature of these modules is the integration of both the switching and low-pass filter stages within a global feedback scheme, yielding a predictable frequency response and distortion regardless of variations in the speaker load impedance. The inset Graph demonstrates the A35.8's unchanging responses into an open circuit (grey) and also 8ohm (black), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads [note the 1kHz-100kHz scale] – other Class D solutions may show wild variations in response under these same conditions [see HFN Dec '21].

The efficiency of Class D operation – over 90% at full output – makes it ideally suited to high power applications, over many channels, without excessive heat or heavy casework. The switchmode PSU, with dual APFC (active power factor correction), also optimises efficiency while keeping weight down to an absolute minimum. Nevertheless, while each stereo 'block' will deliver 2x195W/8ohm the A35.8's simultaneous eight-channel output is necessarily 'limited' by the 1.5kW capacity of the PSU, and efficiency losses, to 8x170W/8ohm or 4x340W/8ohm in bridged mono – surely more than enough for any bi-amp'd system! PM