Pass Labs X350.5 Amplifiers


  • Freq. Response: 0 dB at DC, -4 dB at 100 kHz
  • Power Output: 350 watts
  • Output Voltage Maximum plus
  • Output Current Maximum plus
  • Input Impedance: 22 kohm balanced

User Reviews (1)

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babydoc   AudioPhile [Dec 21, 2005]

A neutral and well-balanced stereo amplifier. Handles most loads and speaker requirements very well. Built like a tank and has safety features such as circuit breaker turn on and off, a useful standby feature. For those who like to display their gear, it has a stunning facade and high quality interior construction as well. Pass's documentation is very good as expected.


It is one brute of an amplifier to move around. This makes some form of mobile base or stand almost mandatory. The speaker terminals are the newer plastic twist and turn; therefore, banana plugs are out. This may be an issue for some users. Due to heat production and large heat sinks, good ventilation with a lot of side and top room is mandatory. This may affect compatibility with some equipment spaces (especially custom designs).

The X350.5 is a beast of an amplifier. It is large and heavy and demands plenty of space. Once you get past the fact that this is a 2-person set up out of the box and warm it up, you get a wonderfully musical product. I have used this amplifier with ESL/hybrids and it makes them sing. The design favors the use of balanced inputs (although single-ended RCAs are also available). It is also noise-free and unlike the old Aleph or newer XA series, does not run scorchingly hot. At normal listening levels, you get the benefit of Class A sound. I have rarely ever gotten it to run past this point, irrespective of source. Once broken in, which takes a couple of weeks of regular use, this amplifier gets the most out of your speakers and seems impervious to complex loads. Fit and finish are first-rate which is important since it will be on display in most systems due to its size and ventilation requirements. I would strongly recommend placing it on a base that can be moved if cable changes or maintenance is needed. SoundAnchors has a custom base that fills this bill. It sounds very similar to the newer Pass products and is not as warm as the old Aleph series nor is it as etched as some of its immediate predecessors. This makes the speaker-amplifier mating process important to audition before purchase as the high frequency characteristics of some speakers will love the 350.5's greater neutrality. A few other points: Due to the current draw of this amp, a dedicated line would be beneficial. It also may benefit from after-market power cords (my 350.5 really liked Nordost Valhalla). This will require some experimentation from potential listeners since home circuits can differ so widely in many regions of the country. In summary, a terrific amplifier that audibly improves on its predecessors in the Pass Labs line. You get many of the benefits of the larger monoblock siblings at a lower price.

Similar Products Used: Pass Aleph 2, 5, X150
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