Pass Labs HPA-1 Headphone Amplifier and Preamp

Pass Labs enters the high end headphone amplifier world with their stunning new HPA-1. Class A single ended with preamp capabilities, this is one headphone amp sure to satisfy even the pickiest audiophile listener! The HPA-1 works well with a wide range of headphones from 20-300 ohms and does very well with Planar headphones such as HiFiMan and Audeze.

Basic Operation

The unit is designed to stay on at all times. The power switch is located in the rear.
When the power is turned on the unit goes into a mute state for twenty seconds, this is to allow the circuitry to stabilize.
During this period no functions are available. During the mute period the power led will flash. When the unit goes out of mute into operate
mode the power led will stop flashing and stay on.
The unit has two inputs that can be selected from the front panel.
The unit also has a preamp function, which is selected from the button on the front panel. When the preamp function is engaged the
headphone output is disconnected, only one output either headphone or preamp is available at any one time.
The unit gets to optimum performance about one hour after turn on.
In the event of a power loss the unit shuts off and upon restoration of power the unit will go through the mute cycle and return to the
state it was in prior to the loss of power. It will remember the last input and function and will return to that setting before the loss of power.
This is also true when the unit is switched off with the power switch.
It is recommended that the unit stay on at all times, if you are away for an extended period of time you could shut the unit off.



Features

Works with headphones with impedances of 15 ohms to 600 ohms
Designed as a power amplifier rather than a typical headphone amplifier to be able to drive low impedance planar phones.
Low feedback wide bandwidth discreet design.
Class A direct coupled Mosfet output stage.
Custom built low noise Torodial power transformer with a Farady shield and peripheral magnetic shield.
Discreet regulated power supply for audio circuits.
J-Fet input stage

Pass HPA-1 Specs

Output Power into 20 ohms 3500mW

Output Power into300 ohms 200mW

Frequency Response 10hz -100k-1dB

Gain8 dB

THD + Noise < 0.005at 1V out

Input Impedance50K Ohm

Output Impedance < 2 ohms

PowerConsumption6 Watts