Little Labs MONOTOR User manual
MONOTOR
Operators Manual
manual printing & pdf formatting 04/2016.
Updated 06/2023
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
ere is lots more in this manual, but please read this even if you do not read manuals;
anks!
e external power supply for the MONOTOR must be the 16-volt 0.3 amp dc regu-
lated bipolar unit supplied with it. If it is labeled 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 is labeled Advanced Power Solutions, it is a linear supply and MUST
BE SWITCHED TO THE PROPER VOLTAGE for the country using it. If you don’t
change the voltage (obvious to some of you), and it is set for 110 volts, and you plug it
into 220 volts, it will BLOW UP the supply, possibly damaging the MONOTOR. If you
set it to 220 volts and plug it into 110 volts, the performance of the MONOTOR will
be severely degraded.
e dc power connector jack used on the MONOTOR looks like a CB microphone
connector. Although dicult to misalign because it is keyed, take care to align the plug
and jack properly when inserting.
e 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-Fi router; the high gain
circuitry, although well shielded in the MONOTOR, will pick up Wi-Fi “chirps,” which
are rectied rf signals. Wi-Fi routers have no place near any high-end audio gear.
e Monotor is vulnerable to failure by extreme static discharge. In dry environments
prone to static, use de-stat on carpets and discharge yourself before touching and placing
headphones on your head. Metal body headphones and planar magnetic phones are
particularly strong static magnets.
e 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. e adapter will connect the ring of the jack to the sleeve. If
making a rca to trs cable, tie the ring and sleeve of the trs to ground and shield with the
tip hot. If making a rca to xlr cable, tie pins one and three together of the male xlr, with
pin two hot.
ank you for purchasing the Little Labs MONOTOR™ source analyzing
professional headphone amp.
e MONOTOR is designed to fulll the need for professional monitoring
at the highest resolution possible, allowing long, fatigue-free analytical
listening sessions.
Headphone listening amounts to 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
but essential.
As a tech at A&M records recording studios and mastering rooms throughout
the ‘80s and ‘90s, 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 unnecessary was deleted; compared to the studios
large mixing consoles going through (necessarily) dozens of ampliers before
reaching your ears, the resolution between the two was readily apparent.
e mastering rooms were very carefully appointed under the direction
of a legendary sta of mastering engineer greats, including Alan Yoshida,
Bernie Grundman, Patricia Sullivan, Dave Collins, Stephen Marcussen,
and others throughout the years. Much of the electronics used were built
in-house. In these rooms, we could analyze minute dierences in the
sonic signature of components; even dierent brands of resistors could be
detected and evaluated for sonic neutrality. ese well-appointed rooms
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, and
reverb tails, which would often go unnoticed in the studio control room
thanks and a little background on the
monotors development
environment—allowing a nal polish to be put on a mix, with the engineer
condent that no matter what system the consumer played it on, all that
would be heard would be what was intended.
Fast forward to 2016, a much dierent 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 suered.
e 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.
e headphone amp in the pro world has been neglected with few oerings,
most of it junk, or the more expensive stu 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. Still, a studio or mastering facility
will typically have much better in-house digital-to-analog converters (the
MONOTOR makes evaluating converters easy).
e USB-powered headphone amp/digital to analog converters are crippled
by default by dc to dc converters used to squeeze every bit of power out
of a USB port.
Internally powered 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.
e 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. e 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. is level of component selectivity allows
for a noticeably improved dynamic range over other headphone amps. You
can drive high-impedance phones to full volume without any strain. e
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.
e 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 wonder what I use for headphones (the headphone eld has
become huge in the last ten years). e 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)! is simple setup will set you back
less than $1000 (slightly more with the Cardas cable) and give you the
performance you could easily spend ten times that trying to achieve, with
most likely worse resolution. Your favorite headphones are more than likely
suitable for the MONOTOR. Another popular headphone used with the
Monotor is the Audeze LCD-X which I love the bass response of. Still,
I’m partial to the neutral mid-range on the HD600. I use for tracking the
closed-back Audo Technica ATH M50. I do not recommend pairing with
the monotor, low impedance, super ecient, typically IEMS (but some
headphones also), which can get too loud too quickly and not give you
adequate volume range on the level control.
So cheers, thank you for your purchase and be sure to look at the rest of
the manual (especially the read this rst part).
anks to all the people for the help, patience, and good insights while
developing this product, e late Zack McCormley (DTS), John Caldwell
(Texas Instruments), Raymond and George 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 ampliers
e front of the monotor has four headphone output jacks (two 1/4”
and two 3.5mm). e 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. Use one set of
phones per stereo amp output for the best performance. But if you need
to use all four, you will not damage the monotor, and the performance
dierence 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
e little holes on either side of the level potentiometer conceal a push
switch set back about an inch. e left switch pushed in bypasses the
left side of the level potentiometer, the right, the right side of the level
potentiometer. ese 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 a Crane song Solaris and
some others). e highest quality level pot is no level pot, and there is no
point in being redundant.
A creative 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 artist’s mic or instrument feeding the right channel. en on the
left channel, bypass the level control so you control that level from your
console, and the artist can use the level on the MONOTOR for a simple
more me, or less me, volume control.
e level control bypass is a great thing to have in certain types of installa-
tions and can add another piece to the puzzle to screw things up in other
installations; 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 mi-
nus 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.
ese 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 the
same results.
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. e 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 45 dB.
In-line monitoring and daisy chaining
Multiple MONOTORS can be used in an installation using trs to trs
cables between units. e XLR/TRS combo jacks and the TRS jacks are
in parallel with one another. is arrangement allows simple in-line mon-
itoring with no need for special Y-type adaptors.
e mini-jack, phones, and talkback
e stereo aux in mini jack can be fed from a phone or any 3.5mm stereo
jack device. is 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 music
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 talkback. When demoing products at
trade shows, sealed back phones are essential. Trying to explain what you
are showing people while wearing phones is dicult. A simple, cheap
stereo Lavalier mic with a mute switch and a wireless transmitter and
base with a headphone out is a simple solution for talkback. Even a super
cheap Behringer micromon ma400 can be used to split out to multiple
MONOTOR stereo aux-ins with a mini splitter like a Belkin rockstar
multi-headphone splitter. Cheap yet very eective.
is setup can be used obviously in any recording situation, but especially
great when 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 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 denitively measured at 0.5 Ω, the reviewer says he mea-
sured 1 Ω); however, I disagreed strongly with the conclusions
drawn by the review writer on some of the measurements. e
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.
Below was my response:
I’m the designer of the Monotor.
I appreciate the eort the reviewer put into measuring the
monotor. It’s interesting and useful. I hope it doesn’t discourage
people from seriously listening and comparing, using their ears
as the nal judge when making a headphone amp purchasing
decision.
I do not dispute the accuracy of the measurements. I do, how-
ever, disagree strongly with the conclusions drawn by the re-
viewer 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 layperson audio fan’s 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,
what specs matter, and what specs are not useful in judging the
sonics of a design.
One can make two identical circuits with dierent chosen com-
ponents that measure identically but can sound very dierent.
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
it will never 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 headphones dynamically to be as transparent to the
source as possible.
ere is a reason a power amplier 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 who says they can perceive an L/R imbalance
of less than 1 dB. Yes, it’s nice when you can nd a simple ana-
log carbon pot that tracks closer than 1dB top to bottom in the
whole logarithmic scale, but if you nd one with 30 steps within 1
dB, you’re doing great. e 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
you added another active step further from transparency. Oh, and
regarding steps, how many more than 30 are necessary?
How much power is necessary for driving a headphone?
I am using both the HD600 Sennheiser (300 ohms) and an Au-
deze LCD-X (20 ohms) daily, and both work wonderfully with the
monotor and certainly without distortion at a very loud volume.
ose 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 unfamiliar with the
Himan HE-400i, but I’ll take the reviewer’s word that the mono-
tor distorted before the HE-400i did.
But, and this is very important, the casual reader of this review
would likely overlook this. is HE-400i is a rare case, a new breed
of headphones with very low sensitivity and low impedance (FYI,
low-impedance phones are typically very sensitive). Another head-
phone with that spec is the Mr. Speaker Aeron (closed back), which I
like a lot. I have never pushed it so loud that 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
drive a well-designed headphone happily. e Monotor has 13.8 dB
of gain. I chose that gain for a perfect pairing with my most popular
headphone, the HD600. at 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.
e monotor is not a one-size-ts-all; you don’t use a Porsche for
o-roading now, do you?
at said, I have some drummer friends who love it super loud and
use the monotor on stage to power their IEMS; they couldn’t be hap-
pier. I worry about their ear health.
Frequency response:
e 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 stu 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:
e monotor found its way into audiophile circles, but it is truly a
pro device.
e mono functions do add greatly to the cost of the monotor. e
phase function makes checking azimuth on tape machines and phono
cartridges a breeze.
e monotor remains balanced, completely dierential internally
through to the output driver. We don’t use any balanced to unbal-
anced buers.
A single active stage is used, surrounded by top-notch passive compo-
nents in a hybrid thru-hole/smt component selection. is circuit
topology includes Dale Vishay thru-hole resistors, Nichicon Muse
bipolar capacitors, polystyrene capacitors, and massive power
supply reserve caps using some of the quietest voltage regulators
available. None of these components add to what can be measured,
but they denitely bring you closer to the source sonically and
makes the unit more costly. I laugh when I hear comments of the
monotor being overpriced. ey 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 the reviewer’s work, but I want to encourage the con-
sumer 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 great.
Cheers,
Jonathan Little
ps
Having now heard the reviewer’s “reference,” I can assure you that
your ears will appreciate my circuit design philosophy.
LITTLE LABS
Los Angeles California
E-MAIL:
WEB:
littlelabs.com
Manual Printing & pdf formatting 04/2016
updated 06/2023
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