Violectric HPA V 100 User Manual page 21

What about the quality of the USB input ?
No matter if it's encoded MP3, CD audio with 16 bit or other audio files
played back from the host, the USB input will also support high quality
audio files with up to 24 bit and 44.1, 48 or 96 kHz sampling rate. The
USB receiver forwards the data to a D/A converter offering 110 dB
dynamic range and –100 dB THD+.
Why does 100% host volume setting make sense ?
Volume control within the host is always accomplished digitally, i.e. bits
are removed from the data stream. Therefore a signal attenuated by
12dB has only 12 active bits left and distortion increases to 0,4 %.
Can the USB signal be utilized any further ?
When the unbalanced cinch sockets of your HPA V100 are configured as
outputs, the converted USB signal is available there in analog form and
can be used to feed further external audio devices, like amplifiers e.g.
See following...
The unbalanced inputs of your HPA V100 can be configured as
unbalanced outputs. This function is provided in active manner - i.e. with
buffer amplifiers - in order to decouple the output signal.
Why does an active feed-through make sense ?
Each electronic device presents input impedance as well as input
capacitance. If several devices would be coupled passively - e.g. with "Y"
adapters - the resulting input parameters could provoke malfunction and
instabilities. A buffer amplifier "reconditions" the signal and makes it
compatible with other devices due to its low-impedance output.
The HPA V100 is DC-coupled, i.e. it can transduce DC voltage as well.
For good measure, a low-cut filter can be inserted by setting the
corresponding jumpers. After input buffering, the signals are forwarded
to a simple 6dB-per-octave filter stage which can be set to two
characteristics: AC (12 Hz), or DC (0 Hz).
Why does frequency bandwidth limiting make sense ?
In signal processing, sound is represented by AC voltages. Sound is
audible - for young people - from about 20 to 20000 Hz. The elder the
listener, the less he will hear high frequencies in particular.
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