Power amplifiers mono — Ubiqaudiolab Ubicube 700

The Ubicube 700 is the biggest and most powerful of three Ubicube mono power amplifiers from Ubiqaudiolab, a Ljubljana company that belongs to the Akrapovič Group, the Slovenian exhaust system maker. Ubiqaudiolab calls the 700 its flagship and says it was conceived to handle the most demanding loudspeaker loads. All units are hand assembled, and stereo playback takes two of them.

Key specs that matter

Rated output is 700 W into 8 ohm, 1,200 W into 4 ohm and 2,000 W into 2 ohm, with stable operation claimed down to 1 ohm. Maximum output current reaches 60 A rms and 90 A peak. The capacitor bank totals 520,000 µF and stores 1,032 J of energy. Bandwidth extends from DC to 500 kHz at the -3 dB points, and gain is +27.75 dB, or 24.4 times the input voltage. At 100 W into 8 ohm THD plus noise stays below 0.01%. Noise lies over 110 dB beneath rated power, and an 8 ohm load sees a damping factor above 500. There is a single DC-coupled balanced XLR input with an impedance of 167 kohm. The cube measures 432 x 432 x 420 mm and weighs 101 kg.

Engineering and use context

Inside, the amplifier works in a bridged monoblock configuration. A DC-coupled, fully symmetrical J-FET input stage runs in class A, followed by a high-bias class AB output stage that stays in pure class A for at least the first 10 W. Ubiqaudiolab matches the lateral MOSFET output transistors by hand to a 1% tolerance and builds its own 700 W power module. An unregulated switch-mode supply with common-mode and differential EMI filtering feeds a Mundorf electrolytic bank, with Jupiter and Duelund copper foil capacitors for coupling and decoupling. The solid aluminium monocoque has several shielded compartments, and thick copper plates inside carry heat away from the modules by chimney-effect airflow. Software watches output current, DC at the speaker terminals, RF interference and module temperature, and a solid-state relay with 0.8 mohm contact resistance disconnects the speakers when a fault appears. The speaker terminals are silver-plated TUM copper. A push button on the top plate handles standby and also steps through the display modes of a 73 dB-range LED power meter with peak hold.

Pairing

With a balanced-only input, any partnering preamplifier must offer XLR outputs. Ubiqaudiolab designed its Ubiquitous 300B hybrid preamplifier to work with these monoblocks, and the company tests its electronics with large loudspeakers such as the Wilson Audio Chronosonic XVX. The current reserve suits speakers with deep impedance dips, while the size and mass of two cubes call for a solid floor and two people for installation.

Alternatives

The Ubicube 400 is the smaller monoblock of the range, rated at 400 W into 8 ohm in a 333 mm cube for rooms where the 700 is too large.