L1.5 Line Preamplifier

L1.5 Straight HIgh (1 of 1)-2-Edit-Edit.jpg

Precision in Control. Transparency in Purpose.

Ch Precision Red 3_4 Reverse Drk Gray Grad.jpg

The L1.5 Line Preamplifier advances the original L1 with a substantially revised signal path, L10-derived input technology, local-feedback Class-A amplification stages, wider DC compensation, and a more sophisticated power-supply architecture. Every stage has been reconsidered to improve temporal stability, lower noise, and preserve the integrity of the source signal as it passes through the center of the system.

Technology with Musical Purpose

The L1.5 reflects CH Precision’s central engineering conviction: technology is meaningful only when it serves the music. Every element of its design was developed entirely in-house, not as an exercise in complexity, but to solve the specific problems a line preamplifier presents at the center of a reference system.

Its relay input selection, L10-derived diamond buffers, fully analog R-2R volume architecture, discrete Class-A gain stages, DC-compensation system, and shunt-regulated power supplies are each engineered for a defined musical purpose: to preserve timing, dynamics, tonal balance, spatial information, and the character of the connected source.

Rather than imposing a stronger identity on the system, the preamplifier gives the listener greater command while remaining transparent to the source and preserving the signal intact.

“For the L1.5, we brought important elements of the L10 architecture into the 1.5-Series platform while reconsidering every critical stage of the original L1. New input buffers, local-feedback amplification, wider DC compensation, and more advanced power regulation allow the L1.5 to deliver greater stability and control while preserving even more of the signal presented by the source.”

—Florian Cossy, CEO

Greater Stability from the First Stage

The electrical integrity of a line preamplifier begins at its inputs. The L1.5 introduces discrete diamond input buffers derived from the flagship L10, with separate hot and cold buffering for balanced signals.

Each buffer uses paired transistors formed on the same semiconductor die. Their close electrical matching and dynamic thermal coupling allow the two devices to respond more consistently as operating temperature changes, improving stability at the first active stage of the signal path.

The rear-panel architecture has also been revised. Removing the former BNC inputs creates sufficient space for the RCA connectors to be mounted directly to the circuit board, shortening the connection between the source and the input circuitry. Together, these changes establish a more direct and stable foundation for everything that follows.

Precision Volume Control

Conventional volume controls often place a potentiometer or switched resistive attenuator directly in series with the music signal. The L1.5 instead uses a fully differential 20-bit R-2R resistor network operating entirely in the analog domain.

The precisely matched network converts the incoming voltage into a proportionally attenuated analog current, adjustable from –99.5 dB to 0 dB in exact 0.5 dB increments. A discrete Class-A current-to-voltage stage then reconstructs the corresponding analog voltage and, only when required, provides 0 dB, +6 dB, +12 dB, or +18 dB of gain. By separating attenuation from active gain, the L1.5 avoids amplifying the signal only to attenuate it again, preserving dynamic range while minimizing unnecessary noise.

Digital Control, Analog Purity

The L1.5 combines sophisticated software control with a signal path that remains entirely analog. Input selection, volume, balance, polarity, mono operation, system monitoring, and app-based control are managed digitally without ever intruding on the pure analog gain stages.

The digital control domain is galvanically isolated from the analog circuitry, preventing noise generated by processors, displays, communications, and control systems from entering the music path. CH Precision’s implementation provides the intelligence of software monitoring and control while keeping its electrical activity completely isolated from the analog circuitry.

This provides the convenience and precision of modern digital control without exposing the analog signal to any digital processing or electrical contamination.

Local Feedback, Precisely Applied

The L1.5 replaces the stage-wide global feedback used in the original L1 with more narrowly applied local feedback, following the architectural approach of the L10.This allows the behavior of each section to be controlled more directly while reducing the interaction and corrective reach associated with a loop extending across an entire amplification stage.

Both stages operate in discrete Class A. The current-to-voltage stage converts the current output of the R-2R volume network back into a voltage signal, while the dual-differential output stage employs five complementary push-pull transistor pairs for each signal polarity. This provides the current capability and low output impedance required to drive long cables and demanding amplifier inputs while maintaining signal stability.

Direct Coupling Without Compromise

The L1.5 is fully DC-coupled, with no coupling capacitors in the signal path. CH Precision’s unique DC-compensation architecture preserves this direct analog connection while controlling offset safely, silently, and musically.

A proprietary circuit continuously measures DC conditions between active stages, then applies ultra-slow correction currents at dedicated points outside the direct signal path. By suppressing DC offset without placing a capacitor in series with the music signal, the L1.5 avoids a source of time-domain modulation—supporting CH Precision’s broader commitment to preserving timing, phase integrity, and the natural continuity of musical events.

A dedicated setup wizard further refines this behavior by accounting for the contribution of the system’s cabling, allowing the L1.5 to maintain silent volume operation and stable DC behavior in the actual installation.

Power Regulation at Every Critical Stage

The performance of an analog circuit depends on the stability of the power supplied to it. The L1.5 uses shunt regulation throughout its critical analog stages, establishing a low-impedance supply environment that remains stable as operating conditions change.

Dedicated shunt-regulated supplies serve the measurement ADCs and DC-compensation DACs, separating these control functions from the discrete audio circuitry they supervise. This approach, also derived from the L10, prevents the measurement and correction systems from modulating the supply conditions of the analog signal path.

The power consumed by the shunt regulators is dynamically optimized, maintaining the electrical benefits of shunt regulation while managing thermal conditions and energy use more efficiently.

Power Regulation and the X1 Upgrade Path

The L1.5 can be further elevated with the X1 External Power Supply. By relocating the transformer, primary regulation, and associated power-supply functions to a dedicated chassis, the X1 removes significant sources of mains-related noise, electromagnetic interference, vibration, and heat from the L1.5 enclosure. Its oversized transformers, extensive filtering, and discrete ultra-low-noise regulation provide a larger and more stable reserve of clean DC power.

The X1 works in concert with the sophisticated local regulation already incorporated within the L1.5, creating successive layers of isolation between the AC mains and its sensitive analog circuitry. This further reduces the noise floor and improves voltage stability, allowing the line stage to respond to subtle changes in signal level without hesitation or obscuration.

The musical benefits are heard not as an alteration of the L1.5’s character, but as a fuller realization of its inherent capabilities. Fine dynamic gradations become easier to follow; instrumental textures are more clearly resolved; spatial relationships acquire greater precision; and reverberation and natural decay emerge from a quieter background. The result is greater transparency, dimensionality, and musical continuity, bringing the listener still closer to the scale, intimacy, and expressive flow of the original performance.

Document and Firmware Downloads

A resource built with the same precision and care that define our instruments, the CH Precision Downloads area provides access to the most recent manuals, firmware updates, spike installation guides, and product brochures. Each document reflects our engineering culture—meticulous in detail, exact in purpose, and designed to ensure that every component performs precisely as intended.

These materials are intended to support owners and partners in configuring, maintaining, and optimising their CH systems. Should you have any questions or require further assistance, we encourage you to contact your authorised CH Precision dealer or reach out directly through our Technical Support form. Our teams are committed to providing the same standard of excellence in service that we apply to our engineering—so that every listening experience remains true to the performance we envisioned.

CB certification confirms that a product has undergone rigorous testing by an independent laboratory and meets internationally recognized electrical-safety standards. For users, it provides added assurance of the product’s safety, reliability, and quality in everyday use. The certificate is available for review below.

The CH Control APP

Available for Apple iOS and Android, the CH Controller provides complete app-based control of CH Precision systems, including input selection, volume, mute, configuration settings, and playback functions. It also allows users to access UPnP devices on the network and browse the music stored there, bringing system control and local music access into a single interface.

Its structure follows the same operational logic as the components

themselves, preserving a direct relationship between front-panel control and the mobile experience. True to CH Precision’s engineering culture, the control platform is designed as an extension of the component architecture rather than a separate control layer. It adds convenience and flexibility while preserving the integrity, precision, and musical priorities that define every CH Precision system.

International Press Honors

The Precision to Disappear

Every source delivers a different combination of output level, impedance, grounding, bandwidth, and dynamic behavior. The preamplifier must accommodate these variables while providing the power amplifier with a stable, low-impedance signal—without altering the musical information between them.

The L1.5 approaches that task through L10-derived diamond input buffers, a differential R-2R volume architecture, gain applied only when required, local-feedback Class-A amplification, direct coupling, active DC compensation, and extensive shunt regulation.

Together, these technologies give the listener authority over the system while eliminating the electronic signature of the circuitry that provides it. Short of the L10, no other CH line stage combines this degree of system adaptability with gain architecture and a volume control purpose-built to preserve the source and bring the listener closer to the musical event. The L1.5 preserves the character of each component, the natural scale of dynamics, and the coherence of every musical gesture from attack through decay. It does more than pass information; it preserves the emotional force within it.

Specifications

General

Type: Line preamplifier
Upgrade path: X1 External Power Supply
Color: Silver standard; Anthracite or Champagne optional
Dimensions: 440 × 440 × 133 mm (W × D × H)
Weight: 20 kg
Operating conditions: 5°C < T < 35°C; 5% < humidity < 85%, non-condensing
Power supply: Selectable 100 V, 115 V, or 230 V AC; 47 Hz to 63 Hz
Power consumption: <0.5 W standby; 55 W nominal

User interface

Display: 800 × 480 pixels, 24-bit RGB AMOLED
Control: Dual-concentric encoder with push function; infrared remote control; Android and iOS apps
Firmware update: USB flash drive or Internet

Analog input

Type: 4 × balanced XLR and 2 × single-ended RCA per channel
Input impedance:
- Balanced: 94 kΩ or 600 Ω
- Single-ended: 47 kΩ or 300 Ω
Maximum input level:
- Balanced: 16 VRMS
- Single-ended: 8 VRMS

Volume and Gain

Attenuation range: –99.5 dB to 0 dB
Adjustment resolution: 0.5 dB
Active-gain settings: 0 dB, +6 dB, +12 dB, or +18 dB
Total operating range: –99.5 dB to +18 dB

Analog Output

Type: 2 × balanced XLR and 1 × single-ended RCA per channel
Output impedance:
- Balanced: 2 × 30 Ω
- Single-ended: 50 Ω
Maximum output level:
- Balanced: 12 VRMS
- Single-ended: 6 VRMS
Bandwidth: DC to >700 kHz, –3 dB; volume at 0 dB; 0 dBu input signal

Total Harmonic Distortion + Noise: <0.0008% (@ 22Hz-22kHz, A-weighted)

Signal-to-noise ratio: >137 dB, 20 Hz to 20 kHz, A-weighted
Output noise: Volume at 0 dB; 27 Ω input termination; 20 Hz to 20 kHz, unweighted
- BBalanced output: <2.0 μVRMS
- Single-ended output: <1.5 μVRMS