Усилители мощности моно — Lamm Industries ML2.2

The ML2.2 is a mono power amplifier of single-ended triode design made by Lamm Industries. It succeeds the ML2.1 and brings an entirely new power transformer, five filter chokes in the power supply instead of two, a new circuit-board material and a completely redesigned input stage based on the topology developed for the Lamm ML3 Signature. The listed price was USD 37,190 per pair and Lamm covered parts and labour for five years on the pair.

Key specs that matter

Rated output is 18 W into 16, 8 or 4 ohm at 0.7 percent THD, and maximum output reaches 21 W into 16 ohm or 20 W into 8 and 4 ohm at 5 percent THD. Small-signal frequency response is 3 Hz to 80 kHz at -3 dB, and at rated power it holds 20 Hz to 20 kHz within -0.3 dB. Input sensitivity is 0.85 V RMS for 18 W into any load, and input impedance is 41 kohm in parallel with 470 pF. Output impedance is 1.68 ohm on the 16 ohm tap, 0.84 ohm on the 8 ohm tap and 0.42 ohm on the 4 ohm tap, so damping stays near 9.5 on every tap. Signal-to-noise ratio is 87 dB referenced to 1 W and 99.5 dB referenced to 18 W, and SMPTE intermodulation distortion is 8 percent or less from 1 to 18 W.

Engineering and use context

In the amplifier section Lamm fits a 12AX7, two 6N6P and one 6C33C-B, while a separate regulation section runs a 5651, a 6AK5 or 5654 and a second 6C33C-B. The 6C33C is an indirectly heated triode first developed as a voltage regulator, chosen for an internal impedance of about 80 ohm, far lower than most audio output triodes, as well as low plate voltage, durability and wide availability, and in the ML2.2 it works from a B+ rail of just 175 V. A custom output transformer couples it to the speaker taps. Plate voltage and current are adjusted through trim potentiometers, with test points on the top plate for a volt-ohm meter. Mains voltage can be switched between 100, 120, 220, 230 and 240 V, and power consumption is roughly 245 W. The 6C33C-B works as the output tube in one position and as the voltage regulator of the output section in the other, while the 12AX7 works as the first stage and the paired 6N6P tubes drive the output triode. Each chassis measures about 210 mm high, 406 mm wide and 518 mm deep and weighs about 36.7 kg.

Pairing

Inputs come through RCA sockets or pseudo-balanced XLR sockets at the front left of the chassis, and a remote turn-on circuit lets compatible Lamm preamplifiers switch the monoblocks on and off.

Alternatives

The Lamm ML3 Signature is a higher-powered single-ended monoblock rated at 32 W, built around a GM-70 directly heated triode with an outboard power supply.