Little Labs LMNOPre Microphone Preamplifier

Jonathan Little retired from the hustle of Los Angeles studios a few years ago and started Little Labs, where he develops studio problem solvers.
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Fast Facts
(click thumbnail)
Applications
Studio, project studio

Key Features
Fully discrete gain stage; completely differential circuit topology from in to out; low frequency resonance control; fully variable phase alignment w/ insert; front panel DI system

Price
$1,680

Contact
Little Labs | 323-851-6860 | www.littlelabs.com

PRODUCT POINTS

Plus

  • Ample gain with low noise for low sensitivity mics and quiet sources
  • Transformer coloration when you want it, transparent when you don’t
  • Interesting possibilities with built-in Phase Alignment adjustment and LF Resonance

Minus

  • A bit pricey
  • Phantom power indicator difficult to see from across the room

SCORE
This is a good tool to add to your collection after you have a few other outboard preampsJonathan Little retired from the hustle of Los Angeles studios a few years ago and started Little Labs, where he develops studio problem solvers. His latest toolbox is a clean, quiet mic preamp, first and foremost. The part that does the work is a fully discrete differential-topology amplifier.

Features

The LMNOPre $1,680 is full of real transistors (as well as some ICs at the front and back ends). There’s not one but two gain control knobs for high and low gain, because the differential topology (two parallel signal paths) requires a dual pot for gain control. Controlling the two gain ranges with a single knob would require a similarly accurate quad pot. The bonus is that you can have two preset gain settings to handle the singer who dives into the mic or a guitarist whose volume changes radically when switching between rhythm and lead.

There are front and rear XLR mic input connectors with a useful switch associated with them. The “Mic Input” switch, as shipped, selects between the front or rear connector. Connect two mics and you can switch between them with the press of a button. The phantom power comes from the preamp side of the switch, so it, too, gets switched between the two connectors. It might have been useful to have the phantom power connected directly to the two connectors, allowing two mics if connected to both be powered and ready regardless of which mic was active. Little knowingly says this will be in the next edition.

An internal jumper allows you to reconfigure the input connectors so that they’re in parallel when the rear connector’s disconnected and the Mic Input switch is engaged. The front connector in this (purist) mode is hardwired to the input transformer, bypassing the switch contacts.

Next comes the custom-built input transformer. There are two pad sets on the circuit board to fit some standard transformer footprints, and Lundahl transformers if you want to try something else. A five-pin XLR connector on the rear panel gives you access to the transformer connections, so you can plug in any transformer you choose. A Jensen DB-E connected backwards is reported to work wonders when using the preamp with a Shure SM57. A recessed rear panel switch selects between the standard transformer and your favorite — either soldered to the circuit board or connected through the XLR.

There’s a switch for phantom power, and a switchable high-pass filter provides 6 dB per octave rolloff starting at 120 Hz, which is more effective at reducing proximity effect than for keeping the sound of passing trucks out of your recording.

The LMNOPre, like most contemporary mic preamps, offers a high-impedance input for an instrument pickup, selectable by the front panel Mic/DI switch. But wait, there’s more! The LMNOPre has a separate input transformer for its DI section. You can connect directly to this transformer though DI input A, though an alternate DI path input (B) puts a FET buffer ahead of the DI transformer. The characteristic sound of the DI transformer is retained with either input impedance.

And now things get interesting. Low Frequency (LF) Resonance is the real mystery function on this preamp. The low-cut filter switch must be engaged in order for it to work, but engaging LF Resonance restores the low frequency response. Adjusting the LF Resonance control makes subtle changes in the low end. According to Little, it’s something he stumbled on when choosing a coupling capacitor. He found that one particular capacitor type gave him a low end effect that was interesting enough to explore, and what he ended up with was this knob.

Little writes in the manual: “It can be used in a subtle way when set to just below the bandwidth of what you are recording. This brings a presence to the signal that is created by the whole waveform basically bouncing at a very low frequency, dependent on the dynamics of what you are miking. This presence is not just a low frequency thing. I think it’s due to a kind of Doppler distortion, but I’m not really sure. The less subtle application is to use it as a proximity effect generator to bring that chesty sound out of wimpy sounding vocals, or anything for that matter (turn a boogie into a marshall). I like to say as a selling point, it can turn Barry Gibb into Barry White.”

The LMNOPre incorporates the same circuit used in the Little Labs’ IBP phase alignment tool. This is not simply an adjustable delay; rather, it’s a real phase shift network in the form of a two stage all-pass filter. Its intended function is correcting the phase cancellation that occurs when combining, for example, a mic and a pickup on a guitar, two mics on an instrument, or when using one mic on a singer and another on his instrument. Intuition tells us that this problem can be corrected by time-aligning the two signals. This is simple with a DAW — just drag one track forward or backward by a millisecond or so, and indeed it seems to work fairly well on things like drums where there’s a large transient component, but the IBP gives a subjectively different result. It’s a tweak control that, in many instances, makes things sound better, and that’s a good thing.

One unusual application for the IBP is a technique known as “phase rotation,” sometimes used in broadcast signal processing. Many voice waveforms (male in particular) exhibit quite a bit of asymmetry. Delay through an all-pass filter is frequency dependent, so overtones are moved in time in a way that makes the waveform more symmetrical, reducing the peak-to-average level by several dB. Overload (or limiting) occurs on the highest peaks regardless of their polarity, so the more-symmetrical waveform can be boosted further than one with higher peaks in one direction than the other without clipping. The frequency response doesn’t change through the all-pass network, so there’s very little noticeable change in the sound. It’s like a free lunch when and where this trick works, allowing you to bring up a vocal in a mix without increasing the overall mix level.

There’s an indicator that tells you when you’re hitting the IBP stage too hard, and the phase alignment section also includes a straightforward polarity reversal switch for situations where it’s needed.

Second OpinionThe cleanliness of a mic preamp is often revealed with vocals, and here the LMNOpre excelled. I threw a variety of solo vocals at it – both male and female voices with ribbons, dynamics and large diaphragm condensers. Clearly defined but never strident, the flat response and clean dynamics of the preamp allowed both vocalists to sound very lifelike and emotionally compelling. I’m sometimes challenged by female backup vocals, but the LMNOpre, an AEA R92 ribbon and an Empirical Labs compressor proved to be silkier, less sibilant and more open than I could ever hope for.

The two gain stages were easy to use and offered plenty of flexibility. I hit the low gain stage with both dynamics and condensers on vocals, guitars and percussion. Quick transients, neutral frequency response and unrestrained dynamics were the order of the day here. I tried the high gain stage with the R92 — nice and hot — and loved it. Theoretical input impedance mismatching aside, this pre was a perfect mate for my ribbon with lots of detail for being so smooth and buttery.

Low frequency resonance (LFR, shall we say) proved to be a useful feature that I’m now a bit addicted to. After achieving my best mic choice and placement, I would switch in the LFR and see if I could improve upon the sound with a little extra girth down low. Sometimes just a touch of LFR (settings of two or three) was sonic perfection on sources like electric guitar and bass. Other times I found myself fearfully trying settings of six or seven to give high-pitched female harmonies more thickness and substance. (Note to self: I must try this on kick or snare!) Far easier than patching an EQ in line and slightly different from proximity effect, now I want all my preamps to do this for me!

The phase alignment control is tricky, but can be very helpful. It’s no substitute for manually time aligning waveforms in your DAW, but does provide a means to check phase coherence and adjust mics as needed. I found such a range of control — way beyond a mere 0 or 180 — to be time consuming and (frankly) distracting as I fiddled with all my double-miked sources (i.e. bass and bass DI).

The heart of this pre is a very, very neutral and open gain stage, but its sheer versatility has bowled me over. These LFR and phase alignment controls are just begging to be played with … with geeky delight! My only quibble is wishing that the HPF had selectable frequency, but then I’d never leave the studio!

— Rob TavaglioneThe output section of the LMNOPre consists of a transformer and Output Level Trim. You can get a bit of saturation grit by driving the transformer hard, and use the “Trim” (attenuator) to bring the output level down to a manageable level to feed the next stage. A front panel switch bypasses if you don’t want the coloration that the transformer adds (it’s really pretty subtle even when driven hard). An overload indicator tells you when you’re driving the preamp section too hard.

There are XLR connectors on the back panel for mic input, preamp output, external transformer connection (5-pin) and a pair of XLRs associated with the IBP circuit. The signal at the “Send” connector is straight out of the gain stage, essentially identical to the LMNOPre output with the transformer and output trim bypassed and the IBP disengaged.

Pressing the Insert Enable switch adjacent to the Return connector switches the IBP input from the preamp gain section to the Insert XLR. This allows you to use the IBP as an independent line level processor for tweaking a previously recorded track, or the insertion of external processors prior to the IBP circuit.

In Use

Once the unit has warmed up there isn’t much to do but plug in a mic, select the right input connector and go.

I found, with the gadgets switched out, the basic sound was quite close to a Great River MP-2H. This isn’t surprising since both use input and output transformers and have the same design goal: clean and quiet amplification with minimum coloration. Having 15 dB more gain than I’m accustomed to allowed me to explore using a couple of particularly low sensitivity mics in situations where they normally don’t work. A stock Beyer M260 about six feet back from my Martin D-18, for example, gave me the best classic Lester Flatt bluegrass backup sound I’ve ever heard in my studio. I could barely tickle the record level meter with my other preamps at that distance.

The LF Resonance is a real wild card. I found it somewhat unpredictable, but kind of fun. It puts a hump in the low frequency response, but the frequency, width and amount of boost varies widely with both the setting of the LF Resonance control and the gain. I could find frequencies where the gain would increase when lowering the Gain control. It seemed in use with real sources to have the greatest audible effect when the gain was set just prior to the output transformer audibly saturating, and finding a LF Resonance setting that pushes it over the edge.

It’s a bit like an adjustable proximity effect when not overused. In the manual, Little describes an extreme setting making something sound like it was miked through a long tube, but I was unable to abuse it in that way. It’s definitely a tweak-to-taste tool.

Is the traditional DAW technique of slipping a track forward or back just as effective as the IBP? The answer: Sometimes; sometimes not. And sometimes combining both techniques is better than using one or the other by itself. On something with a high transient content, for instance top and bottom mics on a snare drum, I’d be inclined to time-align the tracks on the DAW first, then twiddle with the IBP to compensate for the phase shift through the body of the drum. I didn’t have an opportunity to try this, but I’m sure someone will.

The ”Preliminary, unedited” manual is both enlightening and entertaining, suggesting applications for the unconventional tools and controls without guiding the reader through a knob-turning procedure, but rather, encouraging experimentation. It covers all the bases. The only thing I’d add is a block diagram. This would clarify the function of the switches and internal jumpers.

Summary

This is a preamp with tools that you won’t find on any other preamp. They’re effective when used judiciously, and the preamp itself will do any mic proud. That it’s quiet enough to use all of its gain without excessive noise is a credit to the designer. While it’s fairly expensive, it’s in line with the cost of a premium grade mic preamp (which this certainly is) plus the unique stand-alone IBP phase alignment tool. It’s well-built, looks nice and does what it is intended to do.