Modwright LS 100 Preamp

December 2011 Audiophilia review of the LS 100 and KWA 100SE

Positive Feedback 'Best of the Best', by Bob Levi.

Design
The design goal of the Modwright LS 100 was to improve upon the 9.0SE preamp in every way, while keeping the price at a reasonable level. They have done it, in spades. Improvements in sonics, aesthetics and functionality are abundant. All while maintaining the Modwright reputation for impeccable build quality.

The LS 100 is a single-ended design with a 10 function remote control, (2) 6SN7 (Driver) tubes and (1) 5AR4/GZ34(and equivalents) rectifier tube. The LS 100 possesses a single gain/buffer stage, phase inverting, five standard inputs, one Monitor input and tape output, one Home Theater Bypass (HT/BP) input and three main sets of RCA outs.

Lots of add-ins
There is an upgrade slot for an optional in-board DAC or phono stage, a built in headphone amplifier that is fed via the tube driver stage.

The LS 100 is built in the same size enclosure as the KWA 100 amplifier and has the same lines and aesthetics, including backlit logo. Taller enclosure (5") allows for greater range of rectifier tubes to fit inside the enclosure.

Sonically, the LS 100 offers a greater control, ease, musicality and resolution, all perfectly balanced for the ideal musical experience. Frequency response is flat from 20Hz to well beyond 100Khz. Soundstage is extremely wide and detailed, and microdynamics co-exist with a tube warmth and natural musical presentation that must be heard to be believed!

Remote Control Functions Include:

• Power.
• Two remote trigger outputs.
• Selectable balance control, may be bypassed for cleaner signal path.
• Volume control.
• Mute.
• Input select.
• Monitor input select.

Preamp Functions Include:

• Upgrade slot for Optional in-board DAC or Phono stage.
• Internal Class A discrete headphone amp design fed via tube driver stage.
• Home Theater Bypass.
• All pushbutton control - no toggle switches.

The LS 100 is built in the same size enclosure as the KWA 100 amplifier and has the same lines and aesthetics, including backlit logo. Taller enclosure (5") allows for greater range of rectifier tubes to fit inside the enclosure.

Sonically, the LS 100 offers a greater control, ease, musicality and resolution, all perfectly balanced for the ideal musical experience. Frequency response is flat from 20Hz to well beyond 100Khz. Soundstage is extremely wide and detail and micro-dynamics co-exist with a tube warmth and natural musical presentation that must be experienced!

Design Specifications of the LS 100:

• Class A, 'mu'* mu stage variation, for excellent linearity, low distortion and sweet midrange and bloom of tubes without compromise.
• Zero global Negative feedback.
• Direct-coupled input and single MWI custom coupling capacitor in output for the cleanest signal path.
• Low 300 ohm output impedance, allowing for excellent matching with tube and SS amps.
• Star grounding and power supply layout optimized for lowest possible noise floor.
• Pure copper pcb traces, offering the lowest possible impedance.
• Extremely short signal paths and highest quality MWI capacitors and audio grade signal path components for sonic purity.
• Class A, discrete SS Unity Gain headphone impedance matching circuit, allowing tube stage to drive headphones (32 ohm - 600ohm) from any source.

  Phono Upgrade Available Now for $700!

• MC/MM Design

• Internal Dip switches for cartridge loading: 50ohm, 100hm, 500ohm, 1K, 47K, 100pf.

• Passive RIAA filtering.

• Tube-Jfet input stage followed by tube gain/buffer stages.

• Phono board uses (1) 12AU7 and (1) 12AX7.

• Total preamp/phono gain = 66dB (variable via volume control).

• User installable upgrade, via two 20-pin headers/sockets.

DAC upgrade design to follow soon!

NOTE: Either phono or DAC upgrade may be installed, but not both.

Technial Specifications.

• Input Impedance: 39K.

• Output Impedance: 300 ohm.

• Linstage Gain: 13dB (Total gain with Phono = 66dB).

• RCA Line Inputs: 5 pairs.

• XLR Line Inputs: 1 pair (wired single-ended).

• RCA Main Outs: 2 pairs.

• XLR Main Outs: 1 pair (wired single-ended).

• One pair RCA, Tape Out, Monitor Input.

• Two 12V remote trigger outputs.