The "P2X"


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Coming soon!  An all-new tube hybrid preamp / headphone amp (with remote control!) from Apex HiFi!

The "P2X" - a code name that will be replaced with the best name chosen at RMAF - is an all-new tube hybrid design preamp and headphone amp.

Instead of a stepped attenuator or volume control pot, the P2X uses a digitally controlled attenuator using relays and fixed resistors.  This volume control gives nearly perfect attenuation and channel tracking, plus 1dB steps, down to -63dB.

Three inputs are provided, with two sets on RCA connectors at the back and one a 1/8" jack on the front (to connect a phone or music player).  In addition to the headphone jack on the front, RCA outputs on the back provide a preamp output to drive powered speakers or a full stereo system.

All functions of the P2X can be accessed with a single control knob on the front of the enclosure, or by an infrared remote control (included).  Multicolored LEDs on the front of the P2X indicate the volume setting, and by their color, the active input.

The P2X can use many different tubes.  The standard tube is a JJ Electronic ECC802S.  Other tubes that work include any type of 12AU7 or ECC82, 5814, 6211, 5963, 6680, 7057, and 12BH7 tubes.

See it in the CanJam room at Rocky Mountain Audio Fest 2014!

Download the P2X instructions (pdf file) to get an idea of how it functions.



Click on the photos for a full resolution version










Coming Soon

Measurements and Specifications

NOTE:  Please read the page about headphone & amp specs!

Values are typical.  

Max output level into 150 ohms @ 1kHz: 7.2V RMS / 20V P-P / 340mW

Max output level into  33 ohms @ 1kHz: 5.0V RMS / 14V P-P / 750mW

Peak output current: 250mA+

Input impedance: 10k ohms

Output impedance: ~1 ohm

THD+N 1V 1kHz 300 ohms: 0.15% (with stock JJ ECC803S tube)

THD+N 1V 1kHz 32 ohms: 0.15% (with stock JJ ECC803S tube)

FR: 20-20kHz +/- 0.3dB

FR: -3dB <10Hz >50kHz

Attenuator absolute error:  better than +/-0.3dB

Attenuator tracking: better than +/-0.1dB



Power:  85-265  VAC, 50/60Hz, 60watts max.

Dimensions (amp):  3" W x 7" D x 4" tall (including tube)

Dimensions (power supply): 3" W x 6.5: D x 1.75: tall


Attenuator Absolute Error:

Attenuator absolute error



Attenuator Tracking Error:



FFT: 1V RMS @ 1kHz into 33 ohms:




FFT: 1V RMS @ 1kHz into 300 ohms:




Frequency response into 32 ohms:




Frequency response into 32 ohms:




THD vs. frequency into 32 ohms




THD vs. frequency into 300 ohms




THD & Output voltage vs. input voltage (1kHz into 33 ohms):




THD & Output voltage vs. input voltage (1kHz into 300 ohms):