Stereocheck Reviews:

Primare A35.2: Powerful stereo amplifier

Primare A35.2 is a 2 x 200 W stereo amplifier, made using proprietary ultra-fast power supplies using UFPD technology. It provides high output power with extremely low distortion and is ideally...

Primare A35.2
Primare A35.2

Primare A35.2 is a 2 x 200 W stereo amplifier, made using proprietary ultra-fast power supplies using UFPD technology. It provides high output power with extremely low distortion and is ideally matched with the Primare PRE35 audiophile preamplifier and other preamp models, as well as multi-channel audio processors. UFPD power supplies feature minimal peak response time, resulting in natural, clean, fast and transparent sound over an extended frequency range, with excellent overload headroom. In the environmental aspect, the A35.2 is significantly superior to traditional class A/B designs – it significantly exceeds them in efficiency and does not emit excess heat.

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Primare A35.2 consists of two discrete amplifiers, made using UFPD technology and housed in a massive steel and special alloy housing that provides strength, rigidity, shielding and damping of vibrations from external sources. Each channel has unbalanced (RCA) and balanced (XLR) inputs, gold-plated acoustic output connectors, as well as relay inputs and an RS-232 port. The Primare A35.2 easily switches to bridged mode and then delivers one fully balanced mono channel with 800 watts of power into 8 ohms.

Symmetrical signal transmission uses two identical signal lines to transmit the same signal with opposite phase. Any noise present on both lines is present in equal amounts and with the same phase. The receiving differential circuit preserves signals that are out of phase (music) and rejects signals that are in phase (noise), leaving only the pure original signal.

Thanks to this, symmetrical circuits are much better protected from external interference. All switching between bridged and stereo modes, and RCA / XLR inputs is carried out using high quality signal relays. The Primare A35.2 preamp stage is based on Burr-Brown OPA2134 and Analogue Devices AD8512 operational amplifiers with constant gain of 30 dB (unbalanced) and 24 dB (balanced) and a stabilizing impedance of 15 kOhm in a bridged or stereo configuration.

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The rear panel has all the inputs required for a device of this class. Connection via an unbalanced and balanced bus is provided, as well as the ability to work as part of a multi-room control system (there is an RS-232C port). The 12V relay input/output allows this amplifier to be turned on/off simultaneously with the source (eg media player) being turned on/off.

The amplifier is two-channel, but can also operate as a monoblock with many times increased (1×800 W instead of 2×200 W) power – in bridge mode. This mode is implemented using the Bridge switch (located in the very center of the rear panel, next to the toggle switch for selecting unbalanced or balanced input). In this case, the input signal is supplied only to the sockets of the left channel, and the output signal is removed from the positive terminal of the right channel and the negative terminal of the left (the remaining acoustic terminals are short-circuited with a special jumper included in the amplifier kit).

Due to such serious load drops, the output stage of the Class D amplifier ceases to operate stably. To counteract this, feedback is introduced into the UFPD module over the entire operating frequency range, and its depth is adjusted depending on the speaker impedance. Primare engineers claim that this solution allows the amplifier to process signals of any frequency and with very steep edges with equal stability, and also suppress resonances of the output filter, thereby radically reducing distortion.

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Since the UFPD module operates in class D, its efficiency is very high – more than 90% (less than a tenth of the energy supplied from the power supply is converted into heat). In this regard, radiators are no longer needed, and the amplification path can be placed on a very small board. But increased demands are placed on the power supply. In particular, it must absorb excess energy that occurs as the load impedance increases, and, if necessary, on the contrary, increase output. This leads to a complication of its circuit, as well as an increase in the number of storage and auxiliary capacitors, which can be seen in the design of the corresponding amplifier board.

Characteristics of Primare A35.2

Output power (8 Ohms; 0.1% THD): stereo mode – 2×200 W bridged mode – 1×800 W
Analog signal inputs: unbalanced 2xRCA, balanced 2xXLR
Service ports: relay signal input/output 12 V 2×3.5 mm, RS-232C port
Operating frequency range (-0.5 dB): 20 Hz – 20 kHz
Signal-to-noise ratio (20 Hz – 20 kHz, unweighted): 105 dB
THD (stereo): 1 kHz, 100 W, 8 Ohm – 0.005%20 Hz – 20 kHz, 10 W, 8 Ohm – 0.02%
Consumption/Standby: 500 W/0.4 W
Amplifier module: Primare UFPD 2
Power supply: Primare APFC
Dimensions: 430x400x145
Weight: 11.7 kg