Усилители мощности моно — Lamm Industries ML3 Signature

The ML3 Signature is a monaural amplifier from Lamm Industries using a single-ended triode output stage, built as a zero global feedback, pure class A design. Each channel consists of two chassis - the ML3 amplifier and a separate ML3-PS power supply - and the input stage topology developed for this model was later carried over into the Lamm ML2.2.

Key specs that matter

Suggested US retail price was USD 139,290 per pair. Output power is 32 W into 16, 8 or 4 ohm at 3 percent THD, equal to 32 dBW. Frequency response is 20 Hz to 20 kHz, +0 and -1.5 dB, measured at 30 W into 16 ohm. Input sensitivity is 0.85 V RMS for maximum output and input impedance is 41 kohm, with a choice of RCA or pseudo-balanced XLR input jacks. Output impedance ranges from 1.55 to 6.2 ohm depending on the tap in use. Power consumption is around 400 W. The ML3 chassis measures about 210 mm high, 406 mm wide and 518 mm deep and weighs 35.9 kg, while the ML3-PS power supply weighs 36.4 kg, so each mono channel comes to more than 72 kg.

Engineering and use context

A single GM-70 directly heated triode with a plate dissipation of 125 W forms the output stage, and it is fed by one 12AX7 and four 6N30P-DR tubes in the input and driver stages. Rectification takes place in the outboard ML3-PS, which carries six 12AX3 rectifier tubes and six filter chokes together with further power conditioning. The custom output transformer is suspended in vibration-absorbing material to reduce mechanical noise. The front-end and output stages are circuits of Lamm's own design, and the amplifier is specified to drive most real-world speaker loads. Lamm gives service intervals for the tubes - the GM-70 output tube is to be replaced about every 1.5 years, and the 12AX3 or 12BE3 rectifier tubes every 1.5 to 2 years. A stereo installation therefore consists of four chassis - two ML3 amplifiers and two ML3-PS supplies.

Pairing

Lamm introduced the LL1 Signature monaural line-level preamplifier as a complementary component. A preamplifier with RCA outputs or XLR outputs can feed the monoblocks, since Lamm fits both connector types, and loudspeakers are matched through the corresponding output transformer tap.

Alternatives

The Lamm ML2.2 is a smaller single-ended triode monoblock from the same maker, rated at 18 W and based on the 6C33C-B output triode in a single chassis.