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Product Review
 

Lamm L2 Reference Stereo Hybrid Line-Stage Preamplifier

Part I

June, 2007

John E. Johnson, Jr.

 

Specifications:

● Inputs: Two Sets Line, One Set Direct,
   One Pair Rec/In and Rec/Out
● Outputs: One Pair Each XLR and RCA
● Control Chassis Separate from Power
   Supply Chassis
● Power Supply All Tubes: 12AX7, 6C19P,
   5651A, 12AX3
● MFR: 5 Hz - 140 kHz +0 - 3 dB
● THD: 0.03% at 2 Volts Output
● Input Impedance: 51 kOhms
● Output Impedance: 130 Ohms
● S/N: 82 dB at 2 Volts Output
● Dimensions: 4.5" H x 19" W x 13.9" D
   (Each Chassis)
● Weight: 15.4 Pounds (Control Unit); 19
   Pounds (Power Supply)
● MSRP: $14,790 USA

Lamm Industries

Introduction

Ever since I reviewed the Lamm M2.2 Monoblock Power Amplifiers about a year ago, I knew I just had to try out one of their preamplifiers too.

So, I asked Elina and Vladimir Lamm if I could get the L2 Reference Hybrid Line-Stage Preamplifier. Hybrid means it has both tubes and transistors. In this case, the power supply is all tubes, and the control circuits are solid state. In fact, the power supply and control circuits are housed in separate chassis.

I will tell you right now, this is some preamplifier.

The Design

Although the power supply is all tubed, the output stage of the L2 is solid state MOSFET. The entire preamplifier is Pure Class A operation and there is no global negative feedback.

The L2 Reference utilizes a fully balanced design throughout the circuitry, but all inputs are single-ended, which means that inverting inputs of both channels are grounded. However, there are two sets of outputs balanced and single-ended. The designer, Vladimir Lamm, feels that this delivers the best fidelity.

Because the voltage regulator has +350 volts on its plate, Lamm feels the L2 can reproduce the smallest detail. Essentially, because there is so much voltage available, the preamplifier can deliver high voltage transients with ease, even though the average output might only be 1 volt.

Obviously, with a product of this caliber, only the finest parts are used, such as Dale metal film resistors, PRC wire wound resistors, Electrocube and Roederstein film capacitors, Cornell Dublier electrolytic capacitors, TKD stepped potentiometers, and all gold plated contacts.

Attention was paid to making the L2 able to drive any input impedance on a power amplifier, but also to be able to handle the capacitive load of any interconnects, without sonic degradation.

The final design is the culmination of an entire career's experience with audiophile-quality components. The L2 has been in the Lamm line for several years, without modification. There is no need for change.

The power supply and control chassis are separate in order to keep magnetic fields created by the high voltages in the power supply from causing interference in the control circuits.

The front panel has dials and switches on both chassis. These include Power On/Off for the L2, Power On/Off for AC outlets on the rear, Power On/Off for Remote 1 and 2 (turning on the Lamm M2.2 monoblocks for example), Input Selectors, Phase, Line/Direct, Tape/Source, and individual Volume Controls for each channel.

The rear panel has RCA inputs, RCA and XLR outputs, Outlets, Remote Jacks (connects to the Lamm M2.2 monoblocks), multi-pin jacks for a cable that connects the two chassis to one another, and a grounded AC Power receptacle.

The insides of both chassis are shown below. The top photo is the control unit, and the bottom one is the power supply. See the imprint "Danger! High Voltage" in the power supply chassis? That is what makes this product able to deliver the fine detail in music of any type, to any power amplifier. The power amp does not see high voltage, but the muscle potential of the preamp means it can do, no matter what the capacitance of the interconnect.

Go to Part II.

Copyright 2007 Secrets of Home Theater & High Fidelity

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