Little Labs MONOTOR User manual

MONOTOR
Operators Manual

manual printing & pdf formatting 04/2016.
using this manual or any part of it without
permission is a violation of copyright laws.
monotor is a registered trademark of little
labs.

read this first
before using the monotor
There is lots more in this manual, but please read this even if you don't read man-
uals... Thanks!
The external power supply for the MONOTOR must be the 16 volt 0.3 amp dc
regulated bipolar unit supplied with it. If it says INPHASE engineering it is our
new custom made for audio switcher and you don’t need to worry about voltages
in other countries. If it says Advanced Power Solutions it is a linear supply and it
MUST BE SWITCHED TO THE PROPER VOLTAGE for the country using it.
If you don’t change the voltage (this is obvious to some of you) and it is set for 110
volts and you plug it in to 220 volts it will BLOW UP the supply, and possibly dam-
age the MONOTOR. If you set it for 220 volts and you plug it in to 110 volts, the
performance of the MONOTOR will be severely degraded. Blowing up the supply
this way, is not covered by warranty.
The dc power connector jack used on the MONOTOR looks like a CB microphone
connector. Although difcult to misalign because it is keyed, take care to align the
plug and jack properly when inserting.
The 3.5 mini jack sums what is plugged into it with the signal from the main trs/
xlr jacks but after the MONOTORs level potentiometer and mono functions.
So the volume when using this 3.5 mm jack will be controlled by what is feeding it
(e.g., iPod, phone).
Do not place the MONOTOR in close proximity to a wi- router, the high gain
although well shielded MONOTOR will pick up the wi- “chirps.” Wi- routers
have no place near any hi-end audio gear.
The Monotor is vulnerable to failure by extreme static discharge. In dry envi-
ronments prone to static, use de-stat on carpets and discharge yourself before
touching and placing headphones on head. Metal body headphones and planar
magnetic phones are particularly strong static magnets.
The trs/xlr and trs jacks on the MONOTOR are balanced, but the source can be
balanced or unbalanced. For rca plugs you will need a ts (tip-sleeve) to rca adapter,
or a cable made for the purpose. The adapter will connect the ring of the jack
to the sleeve. If making an rca to trs cable, tie the ring and sleeve of the trs to
ground and shield, with the tip hot. If making an rca to xlr cable, tie pins one and
three together of the male xlr, with pin 2 hot.

Thank you for purchasing the Little Labs MONOTOR™ source analyzing
professional headphone amp.
The MONOTOR is designed to fulll the need for professional monitoring
at the highest resolution possible, allowing you long fatigue-free analytical
listening sessions.
Headphone listening amounts for 80% of what the consumer listens
with today, and as the world gets more populated, this percentage will
increase. For the professional mixer, monitoring on headphones is not
only necessary, it is essential.
As a tech at A&M records recording studios and mastering rooms
throughout the 80’s and 90’s, I found the studio control rooms, although
excellent rooms and ne for evaluating a balance, they never came close to
having the high resolution monitoring capabilities of the mastering rooms.
Every component in the audio signal chain of the mastering rooms was
carefully selected and anything not necessary was deleted, compared to
the studios large mixing consoles going through (necessarily) dozens of
ampliers before reaching your ears, the resolution between the two was
readily apparent.
The mastering rooms were very carefully appointed under the direction
of a legendary staff of mastering engineer greats including Alan Yoshida,
Bernie Grundman, Patricia Sullivan, Dave Collins, Stephen Marcussen and
others through out the years. Much of the electronics used were built in
house. In these rooms we were able to analyze minute differences in the
sonic signature of components, even different brands of resistors could
be detected and evaluated for sonic neutrality. This allowed us to have a
mastering chain that would allow an engineer to come in and hear details
such as edits, hums, hiss, unwanted distortions, reverb tails, things that
thanks and a little background on the
monotors development

would get by often un-noticed in the studio control room environment.
This allowed a nal polish to be put on a mix, with the engineer condent
that no matter what system it was played on by the consumer, all that
would be heard would be what was intended.
Fast forward to 2016, a much different recording monitoring environment
is the norm, often makeshift and acoustically imperfect. Despite huge
quality improvements in digital technology, the monitoring environment
has, in most cases, become less than ideal and resolution has suffered.
The Little Labs MONOTOR was designed so two people per MONOTOR
(each headphone out is independently powered) could listen deep into a
track at the highest resolution possible when paired with a quality set of
headphones.
The headphone amp in the pro world has been neglected with few offerings,
most of it junk, or the more expensive stuff available includes the gimmick
cross feed circuitry, and quite often is driven by several active stages with
unsuitable output drivers, great for old consoles to get a guitar sound, but
not for driving high resolution headphones.
Many audiophile headphone amps exist with often euphonic yet inaccurate
reproduction, and at a ridiculous price. A trend of digital to analog
converters combined with headphone amps is also popular. Some of the
digital to analog converters are of decent quality, but typically a studio
or mastering facility will have much better digital to analog converters in
house (the MONOTOR makes evaluating converters easy).
The USB powered headphone amp/digital to analog converters are
crippled by default by use of dc to dc converters used to squeeze every
bit of power out of a usb port.
Internally powered headphones and bluetooth headphones are also crippled
by a neutered power supply.

I’m not saying these headphone amps sound bad, it’s just that they are not
at a level of resolution found in a properly appointed mastering facility.
The Little Labs MONOTOR is designed with what I call a zen circuit
topology. Only a single state of the art active stage is used at its optimum
gain, in the circuit path of each headphone ear, with all else, straight wire
passive (this includes all the mono functions as well). All passive components
in the audio path were selected for sonic neutrality, this includes dale/
vishay resistors, nichicon muse series caps and specialized polystyrene
lm decoupling caps. The MONOTOR uses a full voltage state of the art
super low noise internal linear regulation system (4 uVrms) with massive
capacitance for power on demand on each rail. Just one internal lter
capacitor used (there are 6) is bigger than a whole USB dongle digital to
analog converter/headphone amp. This allows for a noticeably improved
dynamic range over other headphone amps. You will also be able to drive
even high impedance phones to full volume without any strain whatsoever,
and no detectable hiss even at the highest volumes. The MONOTOR when
I say it is state of the art, it truly is, and could not have been built just a
year ago. I’m proud to say, this is not a rehashed old analog circuit, with
this labor of love, we’ve taken analog to another level.
The MONOTOR paired with a good set of headphones will give you a
reference at the highest resolution, so in imperfect environments you’ll
quickly be able to evaluate as you only could in the best mastering facilities.
You might be wondering what I use for headphones, (the headphone eld
has become huge in the last ten years) but the reference I use with the
MONOTOR is the relatively reasonably cost Sennheiser HD600 with a
Cardas cable (cable given to me by Bernie Grundman’s Mastering facility
and ex A&M super tech Beno May, thanks Beno)! This simple set up will
set you back less than $1000 usd (slightly more with the Cardas cable) and
give you performance you could spend easy 10 times that trying to achieve,
with most likely worse resolution. This doesn’t mean your own favorite
headphones aren’t suitable for the MONOTOR, it will drive almost any

headphone to the best of the ability of that headphone. I should note
here the only devices I do not reccomend for pairing with the monotor
are super duper efcient, typically IEMS, which get too loud too quick and
will not give you adequate volume range on the level control.
So cheers, thank you for your purchase, be sure to take a look at the rest
of the manual (especially the read this rst part).
Oh and thanks to all the people for the help, patience, and good insights
while developing this product especially Zack McCormley (DTS), John
Caldwell (Texas Instruments), Raymond, George, and Joyce Lui (G&J mfg),
and my wonderfully supportive amazing girlfriend, Randi Kory.
Happy Listening,
Jonathan Little

The front of the monotor has four headphone output jacks, two
3.5mm and two 1/4” . The two jacks to the left are fed by one stereo
amp and the two jacks to the right are fed by a separate stereo amp.
For the best performance use one set of phones per stereo amp
output. But if you need to use all four, you will not damage the
monotor and performance difference for casual use is minimal.
The little holes on either side of the level potentiometer conceal a push switch set back about an inch. The left switch pushed in bypasses the left side of the level potentiometer, the right, the right side of the level potentiometer. These can be used for a variety of scenarios (see more in the manual). The most common is when using the monotor with a high quality digital to analog converter that has a built in level control (like the Oppo 105). The highest quality level pot is no level pot.
Stereo / mono function switch selects: stereo reverse (maybe that hi hat sounds better on the right?), regular stereo, mono left plus right, left only (in
both ears), right only (in both ears), left minus right for hearing what is out of
phase (between what is feeding the left and right in) and also useful for compressed digital audio file artifact analysis.
front hook up

The xlr trs combo jacks and
trs stack jacks are in paralell
with each other.
Shown here with powered
speakers connected to the
trs jacks used as a thru.
The stereo aux in mini jack can be fed from a phone or any
3.5mm stereo jack device, including ipods or stereo video
camera mic headphone outs (talkback). This input sums with
the main inputs post the mono functions and volume control.
The xlr combo jack inputs to the MONOTOR are typically fed from line level sources such as your stereo buss of your console, the output of your D to A converter, the output of the monitor section of your console, a cd or dvd player, a phono pre amp. a tape machine, or to any line level device you want to monitor. The inputs to the MONOTOR are balanced, but the source can be balanced or unbalanced.
rear hook up

The xlt trs combo jacks and trs jacks
are in paralell with each other.
Shown here with multiple monotors
daisy chained.
The xlr combo jack inputs to the
MONOTOR are typically fed from line
level sources such as your stereo
buss of your console, the output of
your D to A converter, the output of
the monitor section of your console, a
cd or dvd player, a phono pre amp. a
tape machine, or to any line level
device you want to monitor.
The
inputs to the MONOTOR are balanced but the source can be balanced or unbalanced.
daisy chain hook up

special features
Dual ampliers
The front of the monotor has four headphone output jacks (two 1/4”
two 3.5mm). The two jacks to the left are fed by one stereo amp and
the two jacks to the right are fed by a separate stereo amp. For the best
performance use one set of phones per stereo amp output. But if you
need to use all four, you will not damage the monotor and performance
difference is minor for utility use. We use a single volume potentiome-
ter so when doing serious monitoring with a partner, as in listening on
speakers in a room, you will, if wearing the same headphones, be hearing
the exact same high resolution signal.
Little Holes
The little holes on either side of the level potentiometer conceal a push
switch set back about an inch. The left switch pushed in bypasses the
left side of the level potentiometer, the right, the right side of the level
potentiometer. These can be used for a variety of scenarios, but the most
common is when using the monotor with a high quality digital to analog
converter that has a built in level control (like the Oppo 105 and some
others). The highest quality level pot is no level pot, and there is no point
in being redundant.
A more utilitarian scenario is to feed the MONOTOR with it in the
mono L+R mode selected, and a cue mix from the console feeding the
left channel and the artists mic or instrument feeding the right channel.
Then on the left channel bypass the level control, so you control that lev-
el from your console, and the artist can use the level on the MONOTOR
for a simple more me or less me volume control.
The level control is a great thing to have in certain type installations, and
can add another piece in the puzzle to screw things up in other installa-

tions, it is for that reason the bypass switches are concealed.
Stereo reverse, Mono functions, Phase
Stereo / mono function switch selects: stereo reverse, regular stereo,
mono left plus right, left only (in both ears), right only (in both ears), left
minus right for hearing what is out of phase (between what is feeding the
left and right in) and also useful for compressed digital audio le artifact
analysis.
These are switched using relay and switch contacts to do the job, a big
switch, nothing active is added in the process.
As simple as these features are, they are incredibly useful in day to day
use, and far more convenient than using a computer to accomplish.
As Little labs is known for our IBP (in between phase) phase tool, phase
meters frustrated me because they show that something is out of phase,
but not what is out of phase. The L-R function on the MONOTOR lets
you easily hear the audio that’s out of phase, everything in phase between
the left and right channels is attenuated by more than 45dB.
In line monitoring and daisy chaining
Multiple MONOTORS can be used in an installation by using trs to trs
cables between units. The XLR/TRS combo jacks and the TRS jacks are
in parallel with one another. This also allows simple in line monitoring
with no need for special Y type adaptors.
The mini jack, phones and talkback
The stereo aux in mini jack can be fed from a phone or any 3.5mm stereo
jack device. This input sums with the main inputs post the mono func-
tions and volume control.
One scenario to use this is if you have a client who listens to their mu-

sic on their phone. While you have the MONOTOR connected to your
stereo buss, they can plug in their phone and compare your mixes to
what they like, easily using their own volume control for their music and
separately adjusting the stereo buss signal with the MONOTOR level pot
fading each one in and out. It’s an incredibly simple way to hear what the
client is hearing and get them what they want sonically fast.
Another scenario for this jack is talk back. When demoing product at
trade shows sealed back phones are essential. Trying to explain what you
are showing people while wearing phones is difcult. A simple cheap
stereo lavalier mic with a mute switch and either a wireless transmitter
and base with a headphone out is a simple solution for talk back. Even a
super cheap behringer micromon ma400 can be used to split out to mul-
tiple MONOTOR stereo aux ins with a mini splitter like a belkin rockstar
multi headphone splitter. Cheap yet very effective.
This can be used obviously in any recording situation, especially great,
when you are tracking without a proper console.

XLR/TRS input impedances:
Measured in stereo mode with TOA ZM-104 impedance meter.
Balanced signal measured between pin 2-3 xlr or tip ring trs.
Balanced input impedance with level control in 5k-11k Ω *
Balanced input impedance with level control out 8k Ω
Un balanced input impedance with level control in 4k-5k Ω *
Un balanced input impedance with level control out 20k Ω
*Front end passive level attenuator varies input impedance depending
on setting.
Headphone output impedance: 0.5 Ω
Crosstalk @ 1khz balanced mode: >102dB
Crosstalk @ 1khz un-balanced mode: >87dB
Gain: 13.8dB
interface specifications

a word on specs
A review of the Little Labs Monotor headphone amp came out
that was all about measuring the specs. I had no dispute with
most of the measurements (one notably was output impedance
which I denitively measured at 0.5 Ω, the reviewer says he mea-
sured 1 Ω), I did, however, disagree strongly with the conclu-
sions drawn by the review writer on some of the measurements.
The review and measurements can be found here:
http://tinyurl.com/y69gkwak
Doing what I do for 40 years now, I know what specs are im-
portant and what specs are either misleading or not important
for the product being reviewed. This will only be interesting to
my audio friends, but this was my response.
I’m the designer of the Monotor.
I appreciate the effort the reviewer put into measuring the
monotor. It’s interesting and useful. I just hope it doesn’t dis-
courage people from seriously listening and comparing, using
their own ears as the nal judge when making a headphone amp
purchasing decision.
I do not dispute the accuracy of the measurements. I do howev-
er disagree strongly with the conclusions drawn by the review-
er on some of the measurements. In my 40 years of working
professionally designing, maintaining and manufacturing audio
electronics for recording and mastering facilities, I can assure
you a layman audio fanatics biggest mistake is judging a unit to
purchase on specs alone.
As a designer working with professionals with serious listening
chops, you over time learn what makes a circuit sound better
and what specs matter, and what specs are not useful in judging
the sonics of a design.
One can make two identical circuits with different chosen com-
ponents that measure identically but can sound very different.
One can also add to a circuit to make a noise oor even quieter
when the noise is already audibly imperceptible.

One can also add to a circuit to make more current available when
in reality it won’t be used.
Each active addition to a circuit is one step further away from the
purity of the source.
My design philosophy is to use minimum active circuitry in the
signal path to bring the headphone to a respectable volume and
command that headphone dynamically to be as transparent to the
source as is possible.
There is a reason a power amplier makes a poor headphone amp.
You don’t put a dragster engine in a Porsche.
Some notes:
Headphone Imbalance vs. Volume Position.
I challenge anybody out there that says they can perceive an l/R
imbalance of less than 1dB. Yes, it’s nice when you can nd a sim-
ple analog carbon pot that tracks closer than 1dB top to bottom in
the whole logarithmic scale, but if you nd one that has 30 steps
within 1dB you’re doing great. The monotor pot is not a discrete
stepped attenuator, but it tracks pretty damn well for what it is.
Of course, you can use an IC based potentiometer that can track
perfectly, but then you just added another active step further from
transparency. Oh and regarding steps, how many more than 30 is
necessary?
How much power is necessary for driving a headphone?
I am using daily both the HD600 Sennheiser 300 ohms and an Au-
deze LCD-X 20 ohms and both work wonderfully with the mono-
tor, and certainly without distortion at very loud volume.
Those two phones are the two most popular used by professionals
paired with the monotor.
I listen to all genres of music and not once did I notice distortion
even at dangerously high volumes. Now I’m not familiar with the
Himan HE-400i, but I’ll take the reviewer at his word that the
monotor distorted before the HE-400i did.
But, and this is very important, the casual reader of this review
would most likely overlook this. This HE-400i is a rare case, a new
breed of headphone that is very low sensitivity, and also low im-
pedance (FYI low impedance phones are typically very sensitive).

I think another headphone with that spec is the Mr. Speaker Aeron
(closed back), a headphone I like a lot. I have never pushed it so loud
the monotor distorted, but I don’t dispute that you can.
In my experience with headphone amps, voltage gain, which is nec-
essary to drive phones to a respectable level, is far more important a
spec than power output. Rarely is over 100mw of power necessary to
happily drive a well-designed headphone. The Monotor has 13.8 dB
of gain. I chose that gain for a perfect pairing with my most popular
headphone the HD600. That gain with the HD600 gives you a great
range from soft to ridiculously loud, and oh so clean... Now where
that gain becomes a problem is with super sensitive phones, mostly
IEMS. Some IEMS are crazy sensitive, those IEMs I do not recom-
mend with the monotor.
The monotor is not a one size ts all, you don’t use a Porsche for
off-roading now, do you?
That being said I have some drummer friends that love it super loud
and use the monotor on stage to power their IEMS, they couldn’t be
happier. I worry about their ear health.
Frequency response:
The monotor is .3 dB down at 20kHz, at 50kHz it’s 1.7dB down this
is on purpose. I can assure you, you cannot only not hear less than
1dB imbalance left to right you sure as hell can’t hear .3 dB down
at 20kHz. Amplifying stuff that’s not music does not add to a sonic
experience. Overlooked in this review, the monotor has an excellent
low-frequency response, at to 3Hz (where you can actually feel it).
Mono functions and other pro features and price:
The monotor found its way into audiophile circles, but it is truly a
pro device.
The mono functions do add greatly to the cost of the monotor. The
phase function makes checking azimuth on tape machines and phono
cartridges a breeze.
The monotor remains balanced, completely differential internally
through to the output driver. We don’t use any balanced to unbal-
anced buffers.
Only a single active stage is used surrounded by top-notch passive
components in a hybrid thru-hole/smt component selection. This

includes Dale Vishay thru hole resistors, Nichicon Muse bipolar
capacitors, polystyrene capacitors, and massive power supply re-
serve caps using some of the quietest voltage regulators available.
None of these components add to what can be measured, but
denitely bring you closer to the source sonically, and makes the
unit more costly. I laugh when I hear comments of the monotor
being overpriced. They wouldn’t say that if they saw the BOM (bill
of materials).
In closing I didn’t come here to bitch, I came here to enlighten. I
appreciate what the reviewer has done, but I want to encourage the
consumer to look past the spec. Any EE can make textbook audio
gear that measures well, but it takes ears and years to learn what
really sounds well.
Cheers,
Jonathan Little
ps
Having now heard the reviewers “reference,” I can assure you my
philosophy of circuit design your ears will appreciate.

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Manual Printing & pdf formatting 04/2016
Revised 04/19