Предусилители — Lamm Industries LL2.1

The LL2.1 is a vacuum tube line preamplifier from Lamm Industries with a pure Class A topology in which every stage is single-ended from input to output. It is offered in standard and Deluxe versions that share the same chassis, circuit board and parts, the Deluxe having roughly twice the energy storage in its power supply and polystyrene capacitors in critical signal paths.

Key specs that matter

Voltage gain is 7.87 times, plus or minus 2%, or 17.92 dB, and a front panel attenuator reduces it by 15 dB. Frequency response is flat from 20 Hz to 20 kHz and reaches from 1.5 Hz to 400 kHz at the 3 dB points. Distortion is no more than 0.03% at 2 V RMS output and no more than 1% at 30 V RMS. Slew rate is 41 V per microsecond, and unweighted noise is better than 84 dB below 2 V RMS output. Input impedance is 50 kohm and output impedance is typically 250 ohm. Three line-level RCA inputs, one tape loop and two sets of RCA outputs are provided.

Engineering and use context

In each channel a 12AU7A works as the first amplification stage and a 6DJ8 as the second, with a 6X4 or 6202 working as the full-wave vacuum rectifier. The power supply is built with one power transformer, one filter choke and the vacuum rectifier, a combination intended to keep hum and buzz at a very low level, and it accepts 100 to 240 V at 50 or 60 Hz. Other features include a front panel muting switch, a remote on and off function for Lamm power amplifiers, and protection circuitry that mutes the outputs automatically at switch-on and switch-off. The chassis stands 114 mm high, 483 mm wide and 352 mm deep, with handles on the front panel extending 35 mm further. It weighs 9.1 kg, or 16.3 kg in its shipping carton.

Pairing

Having two output sets means the preamplifier can run two power amplifiers when bi-amping, or one power amplifier alongside an active subwoofer, with no splitter cables. The tape loop remains useful for a recorder or an external processor inserted in the signal path. The low output impedance handles ordinary interconnect lengths. All connections are single-ended RCA, so a source or amplifier that only offers balanced XLR sockets would need adapters. The Lamm LP2.1 phono stage shares the same case size for a matched stack.

Alternatives

The Lamm L2.1 Reference is the other line preamplifier in the brand's range.