Things To Know - Violectric HPA V281 User Manual

Things to know ...

Why makes it sense to make such huge efforts ?
A headphone amplifier is a device designed to condition audio signals
with regard to the very specific requirements of headphones. This
doesn't sound too spectacular at the first glance and can be achieved
relatively easily. As with many things however, the devil is in the details
and much more effort is required to design one amplifier for all current
headphone models.
Headphones per se are quite diverse, and there are two essential
parameters: impedance and sensitivity.
In general, headphones with higher impedance can be regarded as less
sensitive than headphones with low impedance (which is not generally
true, but in the majority of cases). The sensitivity of headphones is
usually stated in dB (sound pressure level) per Milliwatt.
Extremes in this sense are the AKG K1000 with 74dB/mW on the one
hand, and the Sennheiser HD25 with108 dB/mW on the other hand:
The K1000 requires 2500 times the power to achieve the same sound
pressure as the HD25.
There is also the fact that headphones with high impedance usually
require much higher voltage to achieve high loudness. Thus the
amplifier must be designed with high internal supply voltages.
Which advantages do balanced signals offer ?
In contrast to unbalanced signals, balanced signals are carried by two
wires (plus ground/shield). In the transmitting device, a balanced signal
is created by generating an inverted original signal (180ˆphase shifted).
The "hot" wire carries the original signal (a), the "cold" wire the inverted
signal (-a). In the receiving device, the balanced signal is processed by
a differential amplifier, which detects the difference between both:
(a) – (-a) = 2a.
On its way between devices, the useful signal can be affected by
interference (s). Interferences however are in phase on both wires and
fed to the differential amplifier as well. Again, the amplifier detects the
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