HeadRoom Micro DAC User manual

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Micro DAC & Ultra Micro DAC
Digital-Analog Converter
Owner’s Manual
Toll Free: 8 0 0 - 8 2 8 - 8 1 8 4
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2020 Gilkerson Drive
Bozeman, MT 59715
www.headphone.com
Congratulations on the purchase of one of the world’s handiest audio products. Able
to buffer USB from your computer for low-jitter smoothness; able to strip S/PDIF digital
data from optical or coax inputs in a single fl ick of a switch; able to source a sweet
analog signal for your favorite headphone or speaker based back-end …it’s Super Micro
DAC! Okay, so we got a bit carried away, but so will you when your digital music so
wonderfully fi lls that space right between your ears.
Because they are functionally identical, both the Micro DAC and Ultra Micro DAC are
covered in this manual. The main difference between them is the asychronos sample
rate converter in the Ultra Micro DAC that increases the bit rate and depth to 192kHz/24
bit data and performs digital interpolation on the data prior to sending it to the D-to-A
converter. That’s some long winded techno-speak for making your digital sources
sound smoother and more natural---more analog and vinyl-like due to smoother digital
data. There’s one heck of an audio beast in that little Ultra Micro DAC enclosure.
Either way you go, you’re getting the best DAC in Cirrus Logic’s lineup; some of the fi n-
est metal-fi lm resistors and poly caps money can buy; and a perfectly lovely way to get
great sound without burning up valuable desktop real estate.
But enough of this chatter! Read on, hook up, and bliss out to your music. You deserve
your reward for money well spent!

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The Micro & Ultra micro DAC Front Panel
1. Input Selector Switch
choose between your digital inputs here. The
input selector switch allows you to have multiple digital sources plugged in to
your Micro DAC all at one time. You can easily switch between your sources
by simply fl ipping this switch to the corresponding input you’d like to hear;
either USB, coax, or optical. Be sure to turn the volume down before switching
between various inputs until you grow accustomed to any volume level changes
that may occur with varying source impedances.
2. Power Switch
When the power is set to ‘on’; the red LED will illuminate
in the center of the HeadRoom logo in the upper left hand corner of the amp.
There is nothing wrong with leaving your amp ‘on’ or ‘off’ for lengthy periods
of time; however we recommed that you unplug your amplifi er if you’re storing
it for a long period of time.
1.
Input selector
switch
2.
Power
Switch
The Micro DAC Front Panel Descriptions
The front panel of the Micro DAC is short, sweet, and elegant; one simple set
of input switches and another power switch along with the HeadRoom logo-
LED are all the grace that front of this simple unit.
Included Power Supply

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5
The Micro & Ultra Micro DAC Rear Panel
1. Line Output
The line out is the best sounding stereo-mini plug out there.
This is the signal source you plug into the input of your headphone amp. You
will need a mini-mini cable to plug from the Micro DAC into the Micro Amp or
other amplifi er with a line input. HeadRoom sells various mini-mini cables;
we highly recommend one of varying lengths offered by Cardas. You can also
use this output to connect your Micro DAC to another amplifi er, home stereo
receiver, or home theater system.
2. Optical Input
The optical input is the fi rst of the digital inputs we’ll
discuss on the Micro DAC, and uses your typical Toslink connector. You get
this input signal from the optical output of your player. Not so many portable
audio players have optical outputs, 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.
3. External Power Input +/- 15VDC Power Input
Plug in your power
supply here. The ‘brick’ power supply is included with the Micro DAC; upon
purchase you will have chosen a voltage appropriate to your country’s volt-
age requirement, either 110v (North America, Japan, Singapore and others)
or 220v (Europe, Australia, China, etc). We also recommend
the Astrodyne
switching power supply or the larger Desktop Power Supply (both accomo-
date any country’s voltage requirement) as available power upgrades, these
upgrades are particularly useful with the Ultra Micro DAC. Visit our website for
more information about these power supply upgrades.
4. Coaxial Input
The coaxial input is your typical coaxial connector. We
recommend using a 75 ohm digital cable when using the coaxial input. Please
visit our website at headphone.com for various coaxial cables. If your Coaxial
cable is a standard size, you will need a mini adaptor that adapts a full size
coaxial connector to a mini size, they are available for purchase on HeadRoom
website, and are called
RCA-Mini Mono adaptor.
5. USB Input
The USB input gets its signal from a computer: laptop, desk-
top, or Ultra-Mobile PC; PC, Mac, or Unix. Most computers will instantly recog-
nize the Micro DAC upon plugging it in, but occasionally some users may need
to go into the audio preferences and select the “USB Audio Codec” as their
primary sound device. You also may need to restart your music playing pro-
gram (iTunes, Windows Media Player, etc) once the Micro DAC is plugged in.
1.
Line
Output
The Micro DAC Rear Panel Descriptions
2.
Optical
Input
3.
External
Power
Input
4.
Coaxial
Input
5.
USB
Input

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Micro DAC
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 fi gure 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 amplifi ers 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 crossfeed 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, benefi t greatly from the processor. Live and classical record-
ings miked from a distance benefi t somewhat less, and can often be listened
to without the processor quite comfortably.
Plain
Headphones
With
HeadRoom
The crossfeed switch in
HeadRoom amplifi ers al-
low you to cross-feed a
little of the left and right
channels across to eacho-
ther through a short time
delay.
Far ear
hears
slight delay.
Near ear
hears sound
fi rst.
30 degrees
off axis
What is the HeadRoom Crossfeed?
Micro DAC & Ultra Micro DAC Common Features
• Multiple Digital Inputs
• +/-15V Power Supply
• DC coupled signal path, from input to output
• Full dual mono design all the way back to the power supply
• Discrete emitter follower ouput stage, biased into class A operation (the Dia-
mond buffer)
• Resistors are low noise, low drift .1% metal fi lm types
• Local device decoupling with low-ESR, tight tolerance PPS fi lm capacitors
• Power supply decoupling with ultra low ESR electrolytics
• Shortest signal path possible, PCB routed with high-speed signal integrity
and low noise in mind
• Multi-layer PCB with dedicated, low impedance power and ground layers
What’s the difference betwen the Micro DAC & Ultra Micro DAC?
The difference between a Micro DAC and Ultra Micro DAC is that the Ultra Mi-
cro DAC uses TI 627 in its output stage and has an Analog Devices AD1896
Asynchronous Sample Rate converter to upsample and the incoming data to
24-bit, 196kHz; smooth the upsampled data with an interpolation fi lter; and
then reclock the data into the DAC with an ultra-low jitter clock oscillator. The
result is smoother data lending toward a pleasing liquid sound more similar
to vinyl and analog.
Micro Ultra DAC
Features & Differences
upsampling
circuitry
current
regulator
diodes

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Connecting your Micro DAC to an Amp
Connecting Your Micro DAC & Ultra Micro DAC
USB Input
USB cable
The most convenient and common way to get a high quality signal out of your computer
is with USB output. (If you have optical or coaxial outputs on your machine, then skip
to the next section.) Simply plug a USB cable into your computer, and plug the smaller
end into the back of the amp. In most cases your computer will instantly recognize
the amplifi er, but you will need to restart your
music management program. If your computer
does not recognize the device, restart; if it still
is not recognized, you may need to go into your
control panel/audio devices or system prefer-
ences/sound output and select ‘USB Audio
Codec’ as your default audio device.
- Switch the Digital Input Selector Switch
to
‘USB’
.
Connecting to your Computer:
Plug the mini-to-mini cable
into the line input of the Amp
and line output of the DAC.
Connecting Micro DAC to Micro Amp:
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Optical cable
Optical Input
To a portable DVD player with Optical Output:
You will need an appropriate optical cable, visit headphone.com to purchase a cable.
Plug one end into your source and connect the other end into the appropriate input
on the back of the amp. (Some DVD players may require you to turn on or activate the
optical output.)
- Switch the Digital Input Selector Switch to
‘optical’
.
Coaxial cable
RCA- Mini
Mono adaptor
To a Home CD player with a Coaxial output:
You will need an appropriate coaxial cable, visit headphone.com to purchase a cable.
Plug one end into your source and connect the other end into the appropriate input
on the back of the amp. If your Coaxial cable is a standard size, you will need a mini
adaptor that adapts a full size coaxial connector to a mini size, they are available for
purchase on HeadRoom website, and are called
RCA-Mini Mono adaptor.
- Switch the Digital Input Selector Switch to
‘coaxial’
.
Home CD player
Coaxial input
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Headphone output
Optical
output
mini-mini
cable
Your Micro DAC should be used with a headphone amp to properly drive your head-
phones with authority. HeadRoom’s Micro Amp or Ultra Micro Amp is designed to be
used with the Micro DAC, but any amplifi er with a line input will follow these same
instructions.
Micro DAC
Micro Amp
Connecting Micro DAC to Amp with RCA Inputs:
If you are using a different amp that has a line input, simply follow the instructions
above. If you are using a headphone amp that provides RCA inputs, then you will need
a mini-RCA cable. Plug the mini end into the output of the Micro DAC, and RCA inputs
into the back of the amp (as always, red or ‘R’ denotes right channel).
Line Input
Line Output
Micro DAC
Mini-RCA cable
Headphone amp
RCA
Inputs
Line Output
You can connect any 1/8” (mini) headphone plug into the heaphone output of your Mi-
cro Amp. (An adaptor is needed if your headphones are terminated to a 1/4” plug.)
Connecting headphones to Micro Amp:
USB Out
Coax Out