REVIEW LITTLE LABS MONOTOR HEADPHONE AMP: The Audio Grail, Sound Purity, for a price

The Little Labs Monotor was not on my radar, my Sweetwater Sales Engineer (Jim S.) put me on to this boutique jewel, made in California. I have Sennheiser HD600 and HD650 headphones in my collection, I typically prefer the HD600 for their clarity but the impedance and load presented by either of these headphones can be challenging for many pieces of gear. In a rare fit of acceptance I said YES and ordered the Monotor without even thinking about the price. Ouch, this little box is not inexpensive but is it worth the price?

This is going to be one of my short reviews because it comes down to two questions:

1. Can you afford this box?

2. Do you have great headphones to drive with it?

If you answer YES to both of these questions then you’re all set, buy one of these and enjoy the clarity, the distortion free sound, the ruler flat frequency response, tight bass, sweet high frequencies, and in general, prepare to enjoy the sweetest monitoring you’ve ever heard. No wonder so many LA mastering-enginears rely on this along with a premium set of headphones. Once you start listening with it you’ll want to use it on everything, Monotor is candy for your ears, it’s what they crave.

Little Labs has a dot-com web address and I suggest you go there, review the information for the “Monotor” Headphone amp and download the owners manual so you can plan the best ways to implement it in your setup. There is lots of information from Jonathan Little (he is the Little in Little Labs).

MONOTOR FEATURES

The Little Labs Monotor is designed to fulfill the need for professional monitoring at the highest resolution possible, allowing you long fatigue-free analytical listening sessions.

What makes the Monotor the exceptional professional’s choice:

• A fully differential, almost entirely passive circuit path, with audio passing through a single active optimum gain stage per output. This circuit topology allows maximum revealing source analysis. Think reverb tails, edits, breaths, details that you have never noticed before. 
• Extensive mono monitoring capability: left plus right, left, right, and even left minus right, for phase check, azimuth, and digital compressed audio file artifact analysis.
• Internal state of the art super low noise linear voltage regulation, with huge reservoir power supply capacitance providing audiophile full current/voltage for accurate, robust defined lows and highs. 
• External custom made for audio bipolar global switching power supply with muscle, plenty of current and power reserve.
• Rack-mountable: Up to 4 Little Labs devices fit in a 1u space.

• Two Separately powered stereo outputs for tandem listening with both 1/4" and 3.5mm jacks, so no adaptors are necessary.
• Quality stepped volume attenuator with internal bypass included for external volume control capability.
• XLR/TRS combo jack inputs in parallel with TRS jacks for easy in-line monitoring and daisy chain multiple Monotor hook up.
• Stereo mini aux input sums with the main audio for talkback communication or easy portable player hookup.

It is easy to talk about all the features packed into this little box (there are a lot), the ability to mono your source in so many ways is very ear-opening for engineers listening for subtle nuances, textures and noise in a recording. 

In the H.o.T. studio, click to enlarge

H.o.T. HEADPHONES TESTED WITH MONOTOR

Sennheiser HD 600 and HD650 — The HD600 have been a favorite for checking mixes since they first came out, their higher impedance design works with the Neve 8816 headphone amp and the Soundcraft console headphone amp but other devices struggle to power these headphones adequately. The Monotor headphone amp turns the HD600 into Xray vision for your ears. I’ve never really understood the HD650, they sound pleasant but lack the sweet high frequencies of the HD600, still the HD650 sound very good with the Monotor headphone amp.

Audio Technica ATH 40 and ATH 50 — the less expensive ATH 40 headphones benefit from Monotor but the bass frequency response of these has always seemed thin and weak. The ATH 50 are a personal favorite, they sound more like ROCK music and work better for tracking use than the HD600 which are open air style. The ATH 50 sound really fantastic with Monotor, tighter bass stands out to a long term user like me. 

Beyerdynamic DT 770 Pro (250Ω) — these headphones are bright and comfortable, two attributes that are great for tracking, plus they work with Neve and Soundcraft headphone amp outputs. Of course they sound better with Monotor driving them but there is not a lot of magic and immense clarity like the HD600. Comfort and natural sound is what these headphones offer in abundance and Monotor makes them sound their best.

$10 Studio Throwaway Headphones — I have a variety of headphones in my collection along with several bargain sets that get used for tracking, I think of these as disposable but they keep working lol. Once again, Monotor even makes the cheapest headphones sound better with more defined bass and clearer upper frequency reproduction (I won't be installing Monotor amps for all the musicians lol).

Beefy Monotor custom power supply, click to enlarge

BUYING ADVICE: If your headphones are weak then replace those first. For critical balance and engineering I’m partial to the HD600 and have used these for several years, I have friends who like other models from Sennheiser even better. I also have a friend who swears by some Sony models which I don't own. The most obvious characteristics you will hear from using a Monotor headphone amp are extended high frequency response, tighter bass, reduced haze and reduced distortion — with a higher end set of headphones (like the HD600) stereo imaging is amazing — if you don’t have quality headphones the real capability of the Monotor won’t be revealed until you upgrade your cans.

Monotor and HD600 Headphones in H.o.T. studio, click to enlarge

EPILOGUE

Monotor is a pricey little headphone amp. There might be other things you need more than this. At an AES back in 1991 Rupert Neve told me that a good set of speakers was the most important piece of kit for your journey. Back then I needed so much, it was tough advice to swallow, but I took it and bought a set of Meyer Studio monitors which I used for over 20 years. 

The Little Labs Monotor, combined with HD600 (or better) headphones makes extremely accurate monitoring a somewhat affordable boutique listening option (compared to buying Meyer monitors) as well as compact and portable. The ability to listen to your mix in many different ways with Monotor provides options that even expensive monitor controllers don’t provide. Monotor has lots of connection options for hooking up to your system. Go check out the Little Labs dot com web site for complete information about the Monotor, grab the owners manual PDF too, it's packed with useful information. Go to your favorite dealer and buy Monotor! Like Uncle Leonard used to say, "You'll thank me, you'll bless me".

Thanks for reading High on Technology, Good Music to You!

© June 2025 by Mark King. It’s not ok to copy or quote without written permission from the author. 

Go forth and create, something beautiful, . . . . .

A Little Box with BIG SOUND!