noise benefits of balanced operation are not accompanied by the degradation of more
semiconductors in the gain path.
The input of the amplifier is flexible and can also be operated with unbalanced sources. The
input system will exhibit full common mode noise rejection with passive balanced sources,
where the negative input is connected to ground at the source through the appropriate source
impedance. This allows adaptation of unbalanced sources to balanced operation with passive
cable connections in a manner that achieves the noise rejection of active balanced sources.
Pin 1 of the XLR input connector is ground, pin 2 is the positive input, and pin 3 is the
negative input.
The Aleph 1.2 is shipped with a shorting plug between pins 1 and 3 of the input XLR
connector. This shorting plug sets the gain of the amplifier to 26 dB when you are using the
RCA unbalanced input. Removal of this plug will set the gain to 20 dB. Needless to say, you
will remove this plug when using the balanced input. There is no penalty for not using this
plug with unbalanced operation, and if you have particularly efficient loudspeakers, you may
find that you prefer it this way.
The slew rate of the amplifier is about 15 Volts/uS under load , which is about 3 times faster
than the fastest signal you will ever see, and about 50 times faster than what you will be
listening to. In and of itself, the slew rate is an unimportant factor when evaluating tube and
simple Mosfet designs. It becomes more important with complex circuit topologies where
there is heavy dependence on feedback correction, but even then its importance has been
overstated.
The amplifier is powered by a toroidal transformer which charges .10 Farad capacitance. This
unregulated supply feeds the output transistors only with a full power ripple of less than a volt.
The power draw of this system is constant regardless of the music playing through the
amplifier. As such, it does not depend on a high quality AC outlet or special power cords,
since the dynamic performance does not create a variation in AC line draw. If the AC line is
running low, the output stage will bias to a higher current level by way of compensation.
The amplifier is stable into any load impedance or reactance including a direct short, and will
deliver clean audio signal into 4 ohms at 600 watt peaks. Into lower impedances it will deliver
approximately 12 amp peaks.
The Aleph 1.2 is impervious to electrostatic shock at the input and dead shorts at the output.
You can safely plug and unplug inputs and outputs while the amplifier is running. (Do not try
this with other products).The Aleph 1.2 is protected from overheating by a 75 degree C.
thermostatic switch, and from internal failure by a slow-blow fuse.
The Aleph 1.2 is warranted by Pass Laboratories to meet performance specifications for 3
years from date of manufacture. During that time, Pass Laboratories will provide free labor
and parts at the manufacturing site. The warranty does not include damage due to misuse or
abuse or modified products and also does not include consequential damage.
