Pass Labs’ Xs Phono Preamplifier costs $45 000 and is a dual-chassis, completely dual-mono phono stage (even the outboard power supply is entirely dual-mono, after the single power cord from the wall outlet).
Xs Phono was an in-house design exercise, developed over the course of over two years with the Pass Labs design team aiming at creating a new reference. Lead designer Wayne Colburn commented, “We tend to do well with products that we want for ourselves. Some of it is purely for us to have a reference.” The XsPhono improves upon Pass Labs’ XP-25 phono stage (US MSRP $10,600) in nearly every way.
Improved shielding (resulting in lower noise), more accurate RIAA compensation, and the use of custom-made capacitors and shock-mounted, gold-clad custom ceramic circuit boards designed for RF applications all contribute to moving the Xs Phono up “into a different league—lower noise, better dynamics, all those things” says Colburn.
The Xs Phono Has three pairs of inputs with each having its own separate, directly connected stereo phono stage with no switches or relays in the signal paths to the first amplification stages. The result is that the Xs Phono (including its dual-mono power supply) contains 13 circuit boards. The Xs Phono is, in effect, three separate phono stages housed in one chassis.
Pass Labs’ Xs Phono Dual-Chassis Phonostage is powered by its dual-mono outboard power supply, the chassis of which has a form factor identical to the XsPhono’s control chassis. The power-cord inlet connects to two totally independent left and right power supplies, each with its own transformer, filtering, and regulation. The control section has its own regulated power supply as well. The power-supply chassis connects to the Xs Phono’s control chassis by means of two power cables fitted with PowerCON locking connectors. The power supply has no on-off or Standby switch, in that the Xs Phono is designed to remain powered-up at all times.
On the front three large knobs control resistive loading, capacitive loading, and gain. Four small buttons provide for input selection, memory recall of settings for all three inputs, high-pass filter (rumble filter), and phono muting.
The Xs Phono allows selection of resistive loading between 30 Ohms and 47k-Ohms; capacitive loading between 100pF and 750pF; and gain between 56dB and 76dB. The active value will always be indicated by an illuminated LED.
The selectable/defeatable high-pass filter or rumble filter imposes a -3dB roll off from 20Hz and below, to remove unwanted sub-sonic frequencies. When the high-pass filter is not engaged, the Xs Phono’s low frequency extension is to below 5Hz.
Xs Phono can output a single-ended (RCA) signal, a balanced (XLR) signal, or both at the same time. This permits, for example, providing a signal to an analogue-to-digital converter or a digital-audio recorder at the same time as to a line stage or preamplifier.
Each of the Xs Phono three pairs of stereo inputs is served by a memory-recall function that saves the settings for resistance, capacitance, and gain. Once the optimal settings for a particular cartridge have been determined, pressing the “Save” button makes those settings the defaults for that input, always engaged upon the selection of that input.