Modwright LS 300 Balanced Tube Preamplifier

ModWright LS 300 Balanced Tube Preamplifier

ModWright's Reference. The Standard Everything Else Is Measured Against.

The LS 300 is the preamplifier that defines what ModWright considers possible. It is the fully resolved expression of Dan Wright's approach to balanced tube preamplifier design — dual mono construction, transformer-coupled inputs, tube rectification feeding separately regulated per-channel power supplies, and a fully differential signal path from input to output. Nothing is shared between channels that doesn't have to be.

When ModWright designed the LS 99, they started here. The LS 300's transformer-coupled input and output topology, its tube rectification architecture, and its 6922 driver circuit all passed directly into the smaller design. The LS 99 exists because the LS 300 proved what the topology was capable of. The LS 300 exists because Dan Wright wanted to know how far that topology could go without constraint.

This is the answer.

The Architecture — Dual Mono, Fully Balanced, Transformer Coupled

Dual mono design means exactly what it says: each channel has its own power supply regulation, its own rectifier tube, its own driver tube, its own signal path. The two channels share a chassis and an outboard power supply enclosure, but from a circuit standpoint they are independent amplifiers operating in parallel. The result is channel separation that a shared-rail design cannot match, and a soundstage stability that reflects it.

The outboard power supply connects via two separate 4-foot umbilicals — one per channel — with 8-pin Switchcraft connectors. Removing the power supply transformers from the main chassis eliminates a significant source of magnetic interference in proximity to the signal stages. The dual umbilical arrangement maintains the channel independence of the dual mono topology all the way back to the power source.

All three RCA inputs are converted to fully balanced differential signals via Lundahl signal transformers before entering the amplification stage. This means the LS 300 operates as a fully balanced preamplifier regardless of whether the connected source provides a balanced output — unbalanced sources receive the same transformer-coupled, differential treatment as balanced ones. The Lundahl transformers also provide galvanic isolation between source and preamplifier, rejecting ground-loop noise and common-mode interference at the point of entry.

The two 6922 driver tubes handle the signal in pure Class A operation throughout. Tube rectification via a pair of 5R4GY tubes feeds the power supply, with solid-state regulation maintaining precision and stability from there. The combination delivers the natural current character of tube rectification with the controlled, consistent output that regulated supplies provide.

Zero global negative feedback. The LS 300 does not use a corrective loop. The circuit performs on its own terms, without the phase artifacts and transient smearing that feedback can introduce.

The Design Goal — and What It Sounds Like

Dan Wright's stated goal for the LS 300 was to deliver the beauty of tubes while maintaining a neutral sonic signature. That is a more demanding brief than it may appear. It rules out the kind of euphonic coloration that makes some tube preamplifiers pleasant but imprecise. It demands dimensionality and harmonic naturalness alongside tonal accuracy and bass control.

The -115dB noise floor — 5dB quieter than the LS 99 — creates the kind of silence around the music that allows the quietest details in a recording to be fully audible. What fills that space is a presentation with genuine three-dimensional depth, stable and precisely located imaging, and the tonal rightness that the best tube designs achieve without exaggerating warmth or adding softness where the music doesn't have it.

The frequency response — flat to 100kHz — means the LS 300 is not shaping anything at the extremes. Bass is controlled and defined. Highs are refined without being etched. The design goal comes through in the result: a preamplifier with the dimensionality and presence of tubes, and the accuracy and authority of a reference design.

Connectivity and Control

The LS 300 is equipped for the most demanding balanced systems while remaining fully accommodating of unbalanced sources.

• 2× XLR fully balanced inputs
• 3× RCA inputs (all Lundahl transformer coupled to balanced differential)
• 1× RCA input doubles as Home Theater Bypass
• 2× XLR fully balanced main outputs
• 2× RCA single-ended main outputs
• Front panel: input select, power, mute, HT/BP, phase
• Remote: volume, mute, power, phase invert
• Tube complement: 2× 6922 / 6DJ8 / 7308 drivers; 2× 5R4GY rectifiers (5AR4, GZ34, 5U4GB, 5V4GB, 274B compatible)

The front-panel phase invert — controllable via remote — allows the LS 300 to correct absolute phase at the preamplifier stage, a refinement that affects imaging stability and is audible on well-recorded material.

Where the LS 300 Fits

The LS 300 is the natural preamplifier for a reference-level ModWright system — paired with the KWA 99 Monoblocks for a fully balanced separates stack, or integrated into a larger system alongside the PH 150 phono stage. Its aesthetics are shared with both the PH 150 and KWA 150SE, reflecting a deliberate design language across ModWright's reference tier.

For listeners who have heard what the LS 99 offers and want to know what the reference topology sounds like without the constraints of the smaller chassis and single power supply — this is that preamplifier.

Specifications

Questions about how the LS 300 compares to the LS 99, or how it fits into your system? We're happy to help you think it through.