Fun Hardware Facts

The X1000 has two power transformers, rated at 1500 watts each, continuous duty at 85 degrees centigrade. Under actual conditions in the amplifier, they will do about 2000 watts continuously each, and at least half again more than that for short durations. The X600 and X350 have one of these transformers in each chassis.

To avoid huge inrush of current during charge up, each of the two transformer primary coils has its own inrush suppressor, which keeps the inrush down to 100 amps or so.

The transformers are potted in steel cans to minimize both mechanical and magnetic noise. The rest of the amplifier is mostly aluminum. This is preferred over steel because steel has a magnetic nonlinearity which induces distortion in analog signal when current is run near its surface. If you have steel in your chassis, you definitely want to keep your analog wiring and output devices away from it.

The X1000 has 8 computer grade (the old large style computer capacitor cans, not the new dinky ones) capacitor cans at 25,000 uF and 75 volts each. These are used to create the unregulated output stage rails at plus and minus 75 volts at 30 amps. The X600 and X350 have 6 of these capacitors, operated at slightly lower voltages.

In the X1000 and X600, a separate smaller transformer is used to provide the additional 20 volts above the rail voltage for the front end circuit. In the X350, this additional voltage is derived from separate windings on the main transformers. This supply is passively filtered so that the ripple voltage is only a few millivolts, none of which shows up at the output. This extra front end supply lowers the distortion and noise of the system, and allows the front end to swing the output stage rail-to-rail with losses on the order of only a volt or so, extracting every last possible watt.

The circuit of the amplifier is completely DC, with no capacitors in the signal path. There are also no slew rate limiting capacitors in the circuit. The high frequency rolloff of the amplifier is controlled by a pair of 4.7 picofarad capacitors.

All the transistors in the product are power Mosfets, actually Hexfets from International Rectifier and Harris. These are hyper-matched parts, with gate voltages matched to 0.5% and all devices taken from the same lot codes (made on the same wafer). Most of the front end transistors, the current sources and cascode devices, are rated at 200 volts and 150 watts. We run them at about 2.5 watts each. The speed critical actual gain devices in the front end, that is to say the actual balanced pair of transistors, are rated at 20 watts, and we run them at a watt each. We keep them on the same heat sink so they have perfect thermal tracking.

The X1000 output stage has 80 and the X600/X350 have 48 output Mosfet power transistors in TO-3 metal packages, again matched to 0.5% and drawn from the same lot codes for each type. The output stages can sustain transients of about 10,000 watts, but are not allowed to dissipate more than 2400 watts for any instant, even into a dead short.

X1000 power is conducted from the power supply capacitors to the output transistors through formed sheets of aluminum having a large surface area and bolted to device cases. Wiring from output devices is attached to the output terminals through 24 parallel runs of 10 gauge copper cable. The X600 and X350 also use this wire for power supply connections. PC

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X600, X350, X1000 specifications

Pass Labs is renowned for its high-quality audio amplification equipment, and their amplifiers—like the X350, X1000, and X600—exemplify their commitment to exceptional sound reproduction and advanced engineering. Each model reflects innovative technologies and distinctive characteristics that cater to audiophiles seeking premium performance.

The Pass Labs X350 is a powerhouse that strikes a balance between power and finesse. It is a Class A amplifier, delivering 350 watts per channel into an 8-ohm load, which translates to incredible clarity and dynamic range across a variety of music genres. One of the standout features of the X350 is its use of the innovative Front End Circuitry, which enhances both linearity and low-frequency response. This ensures that the amplifier can handle complex musical passages effortlessly while retaining the natural timbre of instruments. The X350 also employs the renowned "Pure Class A" operation, resulting in minimal distortion and a warm, engaging sound signature that is particularly pleasing for long listening sessions.

In the range, the X1000 takes performance to the next level. With a staggering output of 1000 watts per channel into 8 ohms, it is designed for those who demand uncompromising power. The X1000 features a fully balanced design, providing superior common-mode rejection and eliminating unwanted noise. This model leverages advanced MOSFET technology, allowing for refined audio reproduction without sacrificing power. The robust build quality, including heavy-duty heat sinks, ensures optimal thermal management, which is vital for maintaining performance during extended use.

If you're in search of an amplifier that combines muscular performance with fine detail, the X600 is a noteworthy option. With 600 watts per channel into 8 ohms, this amplifier takes advantage of Pass Labs' patented technology to deliver nuanced sound without harshness. The X600 also incorporates a unique bias system that automatically adjusts based on the demand of the signal, maximizing efficiency and maintaining sound fidelity. This attention to detail helps in preserving the dynamic range and depth of the audio, making it suitable for both critical listening and casual enjoyment.

In summary, Pass Labs’ X350, X1000, and X600 amplifiers are masterpieces of audio engineering. They each showcase unique technologies and features that cater to a wide range of audiophile preferences—from the balanced performance of the X350, the sheer power of the X1000, to the nuanced detail of the X600. Whether for a sophisticated home theater setup or a dedicated stereo system, these amplifiers stand out for their ability to provide immersive listening experiences that are rich, dynamic, and true to the source.