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Point.8 Series amplifiers deliver high power, fewer stages, lower distortion and less feedback. According to the Foresthill, Calif.-based company, the units accurately represent recording venues with very deep bass and extended highs.
The series consists of five Class-A amplifiers and four Class AB amplifiers, four two-channel and five monoblock models. The two-channel amps include the X150.8, the X250.8, the X350.8 and the XA30.8. The mono models include the X600.8, the XA60.8, the XA100.8, the XA160.8 and the XA200.8. Their per-channel power ratings range from 30 for the two-channel XA30.8 to 600 for the single-channel X600.8.
Inspired by Pass Labs’ X.5 Series amplifiers from 2006, the output stages of the larger Point.8 Series have been designed to bias more deeply into the Class-A operating region. They feature large push-pull Class-A operating envelopes for low distortion and good loudspeaker control at ordinary listening levels.
The Class-A amps employ higher power Toshiba MOSFETs (metal-oxide semiconductor field-effect transistors) than earlier amps. MOSFETs are typically used to convert voltage. Those in the Point.8 Series run at a fraction of their stated specs. The company also installed many more MOSFETs than usual on most Point.8 models. The X250.8 and XA100.8 amplifiers each use 56, while the X350.8, X600.8, XA160.8 and XA200.8 models each use 72.
Pass Labs also improved the amplifiers’ front ends, which house the input and voltage gain stages. Each of the nine Point.8 models has a front end uniquely molded to the specifics of its output stage so that the nine front ends vary in size, voltage, bias current, dissipation, and the distribution of single-ended vs. push-pull bias.
The improvements yield directly coupled (DC) front ends that boast very high stability, low distortion, low noise, 100-Khz open-loop bandwidths, and high input impedances.
The power supplies are also larger than those of earlier amplifiers with a third more storage capacitance as well as new CRC (capacitor-resistor-capacitor) filtering. The power supplies still use paralleled fast/soft rectifiers and large toroidal transformers from Plitron, but the AC primary circuits now incorporate additional RF filtering. Power on/off switching and a stand-by draw are also new. In addition, Pass Labs improved the amplifiers’ output noise by more than 10 dB, and made the amplifiers much more resistant to variations in the AC power line.
The smaller Point.8 models — the X150.8, the X250.8, the XA30.8, the XA60.8 and the XA100.8 — also feature new and larger heat sinks to lower distortion and dissipate the energy of the larger bias currents.
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