ModWright LS 99 Balanced Tube Preamplifier

Every designer's flagship holds the ideas they believe in most. The smart buy is often the model that keeps those ideas and trims everything else. That's the LS 99. Dan Wright took the circuit of his reference LS 300, the transformer-coupled topology, the tube rectification, the regulated supplies, and rebuilt it in a compact two-box design. His own estimate: 95% of the flagship's sound.

The takeaway is simple:

Flagship circuit, compact footprint.

The Design

Two 6922 tubes do the work, running in pure Class A with zero negative feedback. The 6922 is one of the most linear small-signal tubes ever made, and it rewards a simple circuit with low distortion and very low noise.

Lundahl transformers, from Sweden, couple the signal at both the input and the output. That's the heart of ModWright's reference sound. Transformers give the LS 99 true balanced operation from end to end, isolate your sources and amplifiers from each other's ground noise, and let the preamp drive long cable runs with authority. With a 100-ohm output impedance, it handles any amplifier you're likely to pair it with.

Power lives in a separate chassis, joined by a four-foot umbilical. Inside, a 5AR4 tube rectifier feeds solid-state regulation for the high-voltage supply, with regulated DC on the tube heaters as well. Keeping the transformer and rectifier in their own box keeps noise far from the delicate signal circuit, and it shows: ModWright rates the noise floor at -110dB.

The startup sequence looks after the tubes, too. The LS 99 mutes for about 45 seconds while it stabilizes, brings its high voltage up gently, and returns the motorized Alps volume control to zero. Give it 30 to 45 minutes of warm-up and it settles into its best sound.

How It Sounds

We've had the LS 99 in our reference system against the Unico Nuovo, and the LS 99 pulls more information off the recording and places it with more precision. If you want to hear everything your recordings hold, this is a preamp that delivers it.

That resolution comes with real grace. Reviewers who heard it paired with ModWright's KWA 99 amplifiers described a sound that stays natural and rich, finely detailed and never hyped. ModWright's own goal for the LS 99 says it well: the liquidity and holographic imaging of tubes, with tight, deep bass and highs that sparkle without edge or glare.

Connections and Controls

• Two fully balanced XLR inputs and three RCA inputs, chosen with a front-panel rotary selector. One RCA input doubles as Home Theater Bypass.
• Two fully balanced XLR outputs and two RCA outputs.
• Dual 12V trigger outputs, so your amplifiers follow the preamp on and off.
• Front-panel absolute phase switch. The LS 99 starts up phase-correct, and a flip of the switch inverts both channels for recordings that call for it.
• Rear-panel ground switch. One setting runs the XLR outputs fully balanced; the other lets you use the RCA and XLR outputs at the same time, handy for adding a subwoofer.
• Remote control for volume, mute, and the trigger outputs.

Where It Fits

The LS 99 belongs to ModWright's compact "9" series, and at 10.5 inches wide it matches the KWA 99 monoblocks perfectly. Together they share a footprint, a look, and a 12V trigger link that brings the whole system up together. It's also a fine match for any balanced amplifier, and its RCA outputs welcome single-ended amps.

Choose the LS 99 over ModWright's single-ended LS 100 when your system runs balanced and you want transformer coupling. Choose it over the LS 300 when you want most of the flagship's sound in a smaller, more affordable package.

If your stereo shares speakers with a home theater, Home Theater Bypass makes life easy. Your processor's front channels pass straight to the main outputs at the processor's volume setting, and that path stays open even with the LS 99 switched off. Movie night never puts hours on your tubes. Connect only a processor or source with its own volume control to this input.

Every LS 99 is designed and handcrafted in Amboy, Washington, and carries a five-year parts and labor warranty when purchased from an authorized ModWright dealer like us.

Press Recognition

• Twittering Machines (June 2024), Michael Lavorgna, reviewed with the KWA 99 monoblocks. Across three very different pairs of speakers, Lavorgna heard a consistent character he summed up as purity and power: finely resolved and nuanced, natural and rich, and never overly detailed. Read the review at Twittering Machines
• Stereophile, Pacific Audio Fest 2023 show coverage. At the LS 99's debut, paired with the KWA 99 monoblocks, Stereophile heard an extremely quiet system with lovely sound and an attractive midrange that combined warmth with clarity. Read the show report at Stereophile

Weighing the LS 99 against the LS 300 or the LS 100, or wondering how it will match your amplifier? Give us a call. We'll help you sort it out.

Specifications

• Type: Fully balanced tube preamplifier, two-chassis design
• Gain stage: Pure Class A, zero negative feedback, Lundahl transformer-coupled input and output
• Tube complement: 2 x 6922/6DJ8/7308/E88CC (signal), 1 x 5AR4/GZ34 (rectifier)
• Rectifier substitutions: 5R4GY, 5U4G, 5U4GB, 5V4G, 5V4GB, 274B and equivalents
• Power supply: Outboard, tube rectified, input current regulated, discrete FET regulated B+, regulated DC heaters, soft-start
• Gain: 11dB
• Frequency response: 20Hz to 150kHz, flat
• Input impedance: 30k ohms
• Output impedance: 100 ohms
• Noise floor: -110dB (unweighted)
• Inputs: 2 pairs XLR (fully balanced), 3 pairs RCA (one doubles as Home Theater Bypass)
• Outputs: 2 pairs XLR (fully balanced), 2 pairs RCA
• Triggers: 2 x 12V outputs
• Volume control: Motorized Alps potentiometer
• Controls: Rotary input selector, volume, power, mute, absolute phase, Home Theater Bypass, rear ground switch
• Remote control: Volume, mute, trigger outputs
• Dimensions, preamp: 10.5" W x 4.5" H x 12" D (depth includes knobs and RCA jacks; height excludes tubes)
• Dimensions, power supply: 7" W x 3" H x 9" D
• Weight: Preamp 17 lbs, power supply 11 lbs (33 lbs combined shipping)
• Umbilical: 4 ft, 8-pin Switchcraft connectors
• Power: IEC inlet, 120V/60Hz standard
• Finishes: Black, Silver
• Warranty: 5 years parts and labor from an authorized dealer, non-transferable
• Designed and handcrafted: Amboy, Washington, USA