Following in the BSC design tradition the L5 represents a different approach to conventional preamplifier design.
• Fully discrete, differential, and complimentary Class A circuitry from input to output.
• 255 step, discrete, differential, motorized, linear volume control.
• 3-chassis all isolated and individually mounted on a single base containing, (i) Power Supply module, (ii) Main Audio module, and (iii) Control & Processing module.
• Separate, ultra-stable, and discrete power supplies. The digital power supply is based on a 75 VA toroidal transformer. The analog supply is based on a massive 150 VA toroidal transformer.
• Future additions to the preamplifier functionality will include dealer installable internal plug-in boards for (i) active 3-band differential tone controls and (ii) phono preamplifier.
Multiple chassis Design
The L5 preamplifier is not the first preamplifier to adopt a multi-chassis solution for noise and crosstalk contamination, but may be the first to consolidate it. At BSC, external power supplies are an elegant solution to reducing noise, we took it a step further and isolated the digital control circuitry in a separate box of its own as well. In this configuration the Analog and Digital sections of the preamplifier are completely isolated. The power supply consists of two separate sections one for the analog circuitry, input / output stages and one for the digital electronics and relay logic. The problem with external boxes is where to put them in your over crowded rack. We provide an integrated Base that unites the three separate chassis onto one pedestal. Additionally all of the wiring that is exchanged between the boxes is neatly tucked inside of the base, and only a short hidden cable is connected to each separate chassis.
The power supply chassis is comprised of two separate sections. A high current regulated Analog power supply with a 160Va toroidal transformer and a high current double regulated Digital power supply with a 50Va toroidal transformer. Each power supply circuit is 2oz copper and further isolated via two discrete power output connectors.
The input stages of the L5 preamplifier are all discrete, complimentary, Class A differential circuits. The first input gain stage has extremely High input impedance, allowing a very simple load for any front end component. All circuitry remains differential through out the entire preamplifier.
The centerpiece of the L5 preamplifier is the volume control. From the motorized linear volume mechanism to the discrete precision R2R resistor network, no expense was spared. The linear volume control was directly influenced from my days working with recording consoles. The idea of a flying fader was intriguing in regards to the instant visual stimulation it offers as well as the precision control. Unable to find a suitable linear fader control that could offer the tracking precision between four channels proved to be impossible. After the exhaustive search, we decided to build our own. A cage machined from a solid block of aluminum houses the linear bearing based slide mechanism and associated components. A high speed, high torque DC motor controls the linear motion through a kevlar belt. Volume position is indicated via a precision optical encoder that selects the correct resistor value combination for the given gain selection. A R2R switched resistor array consist of several resistors switched via precision relays in combinations to raise or lower signal level. This in our opinion is is the very best way to attenuate levels in a high performance audio product.
The output stage of the L5 preamplifier is an extremely fast and powerful, easily able to drive extra long lengths of interconnect cable and an amplifier front end.
Price: USD 15,900.00