ModWright LS 100 Tube Preamplifier

You want tube sound in your system. You also want a remote, a headphone jack, a clean way to bring in your home theater, and room to add a turntable someday. The LS 100 gives you all of it, built around one simple idea: a single 6SN7 tube stage between your source and your amplifier.

If you remember one thing about it, it's this:

Purist tube sound, everyday convenience.

One Stage, Done Right

Dan Wright built the LS 100 around a single gain and buffer stage per channel, each one a 6SN7. That tube has a long reputation among listeners for midrange body and soundstage depth, and it earns it here. One stage gives the signal the shortest possible path, with fewer parts shaping what you hear.

Power comes from a 5AR4 tube rectifier feeding a solid-state regulated supply. The tube rectifier brings voltages up gently and lends the sound its ease. The regulation holds those voltages steady while you listen. You get both.

Gain is 11dB. That suits modern sources, which already deliver plenty of signal, and it keeps the noise floor low. The practical payoff is a volume knob with real usable range, especially with sensitive speakers or high-gain amplifiers.

The sockets make the LS 100 easy to tailor, too. Any 6SN7 or CV181-compatible tube fits, and the rectifier socket takes the 5AR4/GZ34, 5U4GB, or 5V4GB. ModWright recommends Sophia Electric 6SN7s and Dutch-made Mullard, Amperex, or Philips GZ34 rectifiers. A tube swap is one of the smartest, most affordable ways to fine-tune a system you already enjoy.

How It Sounds

To our ears, the stock LS 100 is neutral in its presentation, with a naturalness that allows for long listening sessions without fatigue. Resolution is smooth and detailed, and if you need more warmth, you can roll the 6SN7 tubes.

Reviewers keep landing on the same word: clear. Voices come forward with real presence, the midrange opens up with fine detail and a clean, grain-free texture, and the top end stays smooth without going soft.

That makes the LS 100 a smart pick for listeners who want tubes for their naturalness and still want to hear exactly what their sources are doing.

Connections and Controls

The back panel covers a full system:

• Four RCA inputs and one XLR input (CD, DVD, Video, Aux 1, Aux 2). The XLR input is wired single-ended.
• A monitor input and a tape output.
• A Home Theater Bypass input.
• Two RCA main outputs and one XLR main output (wired single-ended), ready for two amplifiers or an amplifier and a subwoofer.
• Two 12V trigger outputs for switching amplifiers on and off with the preamp.
• An upgrade slot for the internal phono stage.

The remote runs power, volume, mute, input and monitor selection, balance, and both triggers. Every front-panel function is a pushbutton. At power-up the balance control sits out of the circuit for the cleanest signal path, and you switch it in only when a room calls for it.

The headphone amplifier is a discrete Class A design fed straight from the tube stage, with 1.5 watts into 32 to 600 ohms. Late-night listening keeps the same tube voice as your speakers.

Add a Turntable Anytime

ModWright's internal phono board plugs into the upgrade slot, and you or we can install it. It runs on one 12AX7 and one 12AU7, handles moving coil cartridges as delivered, and moves to moving magnet gain with a simple swap of the 12AX7 for a second 12AU7. Loading options from 50 ohms to 47K are set with internal DIP switches. Start with line-level sources today and grow into vinyl on your own schedule.

Where It Fits

The LS 100 is ModWright's single-ended preamplifier, sitting below the fully balanced LS 99 and LS 300. It's the smart choice when your system runs single-ended, when you want tubes and a quality headphone amp in one chassis, or when your home theater and your stereo share the same front speakers.

That last case is where Home Theater Bypass shines. It sends your processor's front left and right channels straight to the main outputs, around the LS 100's circuitry and volume control. Movies play at the processor's volume setting. Music plays through the tubes. Connect only a processor or source with its own volume control to this input.

One setup note: like many single-stage designs, the LS 100 inverts absolute polarity. Reverse the leads on both speaker cables, at the amplifier or at the speakers, and your system is back in correct polarity.

Every LS 100 is built by hand in Amboy, Washington, and carries a five-year parts and labor warranty when purchased from an authorized ModWright dealer like us.

Press Recognition

The LS 100 has earned a long run of praise from reviewers in the US and Europe. A few highlights:

• Positive Feedback, Issue 78 (April 2015), Larry Cox. Cox heard the LS 100 as clear and well articulated, closer to neutral than romantic, and singled out the home theater bypass as the feature that finally let one set of speakers serve both his movie and his music systems. He called it a preamp he could have happily lived with for more than a decade, closing with "I stand impressed." Read the review at Positive Feedback
• The Ear (February 2014), René van Es, reviewed with the KWA 100SE amplifier. Recommended. Van Es praised a wide-open, detailed midrange free of grain, a smooth top end, and a presentation transparent enough to reveal exactly what each source adds. He found it so tonally even that you might never guess it runs on tubes. Read the review at The Ear
• 6moons, Srajan Ebaen, reviewed with the KWA 100SE amplifier. Ebaen paid special attention to the built-in headphone stage and its discrete, feedback-free design, and noted that the LS 100 had already collected best-of-show nods across several publications. Read the review at 6moons

Wondering whether 11dB of gain suits your amplifier, or whether the phono board makes sense for your cartridge? Give us a call and we'll work through it with you.

Specifications

• Type: Single-ended tube preamplifier
• Circuit: Single gain/buffer stage, phase inverting
• Tube complement: 2 x 6SN7 (driver), 1 x 5AR4/GZ34 (rectifier)
• Tube substitutions: Any 6SN7/CV181-compatible driver; rectifier also accepts 5U4GB and 5V4GB
• Power supply: Tube rectified, solid-state regulated
• Gain: 11dB
• Input impedance: 38k ohms
• Output impedance: 300 ohms
• Frequency response: 20Hz to 100kHz (±1dB)
• Maximum input level: 10V rms
• Maximum output level: 37V rms
• Inputs: 4 pairs RCA, 1 pair XLR (wired single-ended), 1 pair RCA monitor, 1 pair RCA Home Theater Bypass
• Outputs: 2 pairs RCA main, 1 pair XLR main (wired single-ended), 1 pair RCA tape
• Triggers: 2 x 12V outputs
• Headphone amplifier: Discrete Class A, tube-fed, 1.5W into 32 to 600 ohms
• Remote control: Power, volume, mute, input select, monitor select, balance, triggers
• Optional phono stage: MM/MC, 1 x 12AX7 and 1 x 12AU7, gain 63dB MC / 48dB MM (including line stage), loading 50, 100, 500, 1K, 47K ohms and 100pF, 1 pair RCA inputs, user or dealer installable
• Power: IEC inlet, 120V/60Hz standard
• Dimensions: 17.75" W x 17.5" D x 6.5" H
• Weight: 25 lbs (31 lbs shipped)
• Finishes: Silver, Black
• Warranty: 5 years parts and labor from an authorized dealer, non-transferable
• Designed and built: Amboy, Washington, USA