6
7
What is the HeadRoom Crossfeed?
Imagine you are listening to a pair of speakers. If you turn off the left speaker,
both ears hear the sound from the right speaker. But because the left ear is
slight farther away than the right ear, it hears the speaker’s sound slightly
after the right ear; about 300 microSeconds. This time difference is called the
“inter-aural time difference” and it is the main thing your brain listens for in
order to tell where to place sound left-to-right.
But in headphones if you turn off the left channel, only the right ear hears the
sound. In headphones, if there is any sound that is only in the left channel, or
only in the right channel, then only that ear hears the sound. This is not natu-
ral, and you brain becomes fatigued trying to figure out where sound is com-
ing from when only one ear is hearing it. This tends to create an audio image
that is a blob on the left, blob on the right and a blob in the middle.
HeadRoom amplifiers cure the problem by allowing you to cross-feed a little
of the left and right channels across to each other through a short time de-
lay using the processor switch. The usefulness of the circuit varies depending
on what type of recording you are listening to; mono and binaural recordings
need no processor at all. Old studio recordings that have instruments panned
hard left or right, benefit greatly from the processor. Live and classical record-
ings miked from a distance benefit somewhat less, and can often be listened
to without the processor quite comfortably.
Plain
Headphones
With
HeadRoom
The crossfeed switch in Head-
Room amplifiers allow you to
cross-feed a little of the left and
right channels across to eacho-
ther through a short time delay.
The Digital-Analog Convertor Option
When purchasing the Desktop Portable Amp, you have the option of including
a DAC. If you did not purchase the DAC option with your amp initially, you can
have this upgrade performed at a later date.
The Desktop DAC is a clean, well-balanced, and natural sounding converter. It
uses the Cirrus Logic’s flagship CS4398 24bit/192kHz, 120dB dynamic range
digital to analog converter. Coupled with extensive power supply isolation
and regulation this DAC will take virtually any digital source and turn it into a
quality listening experience.
The Desktop DAC board uses the well regarded Burr-Brown 134 in single pack-
ages; only metal thin film resistors and polyphenylenesulfide (poly film) ca-
pacitors are used anywhere near the audio circuits. Three low-noise, ultra-
low dropout power supply regulators isolate the various digital, analog, and
mixed signal circuits.
9.
coaxial input
8. USB input
10.
optical input
7.
digital input
selector
6.
source selector
6. Source Selector
When using the DAC, you will need to choose whether
you are using a digital input or an analog input. The source selector switch al-
lows you to have both digital and analog sources connected at the same time,
and you may change between the two with a simple flip of this switch.
7. Digital Input Selector
When using the DAC, the digital input selector
allows you to choose which digital input you would like to listen to.
8. USB Input
The USB input gets its signal from a computer: laptop or desk-
top; PC, Mac, or Unix.
9. Coaxial input
The coaxial input is your typical coaxial connector. We
recommend using a 75 ohm digital cable when using the coaxial input.
10. Optical Input
The optical input is your typical Toslink connector. You
get this input signal from the optical output of your player. Not so many por-
table audio players have optical outputs anymore (call or check our web site
for recommendations), but many portable DVD players and some hard disk
drive players do. Of course, you can get this signal from many pieces of home
equipment.
Far ear
hears
slight delay.
Near ear
hears
sound first.
30 degrees
off axis
