CH Precision L1.5 Line Preamplifier

The L1.5 replaces the L1 as CH Precision's 1-Series linestage, advancing the design with technologies developed for the reference L10.

Input buffering uses discrete diamond circuits derived directly from the L10 -- paired transistors formed on the same semiconductor die for close electrical and thermal matching. This improves stability as operating temperature changes. Relay input selection and directly mounted RCA connectors keep the path between source and input circuitry as short as possible. Discrete Class-A amplification applies local feedback within individual circuit sections, and a powerful dual-differential output stage provides the current delivery and low output impedance needed to drive long cables and demanding amplifier inputs.

Volume control is a fully differential 20-bit R-2R resistor network operating entirely in the analog domain. Attenuation is adjustable from -99.5 dB to 0 dB in 0.5 dB steps, with selectable active gain of 0, +6, +12, or +18 dB. Because attenuation and active gain are handled separately, the L1.5 preserves dynamic range at any listening level and avoids unnecessary amplification.

All system management -- input selection, volume, balance, polarity, mono operation, and monitoring -- is handled digitally, with the control domain galvanically isolated from the analog circuit. Processor, display, and communication activity are kept away from the music signal. The front panel offers a dual-concentric control, and the CH Controller app for iOS and Android provides full access to configuration and daily operation. An infrared remote is also included.

Power regulation is more sophisticated than the L1. The L1.5 uses dedicated shunt regulators for critical analog stages and a high-current series regulator for the output stage. Two additional shunt regulators -- one for DC measurement, one for DC correction -- prevent those functions from affecting the audio supplies. The optional X1 External Power Supply moves the transformer and primary regulation entirely out of the chassis, reducing mains-related interference, vibration, and heat at the source.

Existing L1 owners can upgrade their units to L1.5 specification. Contact us for pricing. Note: L1 units manufactured before 2020 may also require a display upgrade.