Power tube monoblocks of the American company Manley Labs.
The amplifier consists of two separate monoblocks, each of which has a nominal power of 250 W in ultra-linear mode and 125 W in triode mode. Unlike most amplifiers, where taps are installed in the secondary winding of the output transformer for optimal matching of power output in speakers with different impedances, which leads to a deterioration in sound quality with an increase in dissipation inductance, the output transformer in the Manley 250 is designed for a load of 5 Ohms, which provides full flux coupling between the windings of its output transformer. But the main feature of the design of the amplifier is the powerful two-stroke output cascades, in each arm of which 5 lamps are connected in parallel. Such a departure from the classic engineering canons made it possible to obtain significant power for a tube amplifier on the popular EL34EH in a relatively simple way. The second decisive step, implemented in the design amplifier, it is possible to switch the output stages from the typical ultra-linear mode to the triode mode. Normal operation of the output cascades on parallel lamps can be carried out only if their parameters are identical. Even in carefully selected lamps, the parameters change differently during operation. That is why during operation it is necessary to periodically adjust the modes, which is provided for in the design of the amplifier. 10 adjusting resistors are placed on the front panel, which regulate the bias voltage on the control
grids of lamps, and the same number of control sockets for connecting a simple measuring device. The adjustment procedure is described in detail in the manual and is available to any audiophile. The following types of lamps are recommended for optimal sound.
Ten EL34, two 12BH7 and one 12AT7 lamps work in each monoblock. The lamps are installed in the front part of the chassis, inside the amplifier case, behind them - the output transformer and the power supply unit with a power transformer. On the front panel there are: a mute switch, an "ultraline - triode" switch, a power switch with "soft start" mode, as well as a standby mode switch. On the rear panel there are: a standard connector for connecting a power cable, an RCA - XLR input switch, an unbalanced RCA socket and an XLR - balanced input connector, as well as output terminals for connecting speakers.
By switching the triode - ultra-linear mode, the listener has the opportunity to change the character of the sound of the system, to choose between the softness and warmth of the triode and the power and density of the ultra-linear modes.

Specifications
Used lamps
- in output stages EL34G, EL34G +, EL34WXT or EL34EH.
- in driver cascades: 12Н7А, 12ВН7, 12ВН7А or 6414.
-in input cascades: 12AT7WA
Output power: 250 W (ultra-linear), 125 W (triode)
Type of amplifier: Push-ball (two-stroke)
Functions: "Soft-start", "Ever-Warm".
Frequency range with uneven frequency response ± 0.5 dB: 10-80,000 Hz
Input sensitivity: 1 V
Inputs / outputs: BALANCED ; UNBALANCED.
Input resistance: 100 kΩ
Power: 30 W - minimum, 815 W - maximum
Dimensions (h x w x d): 178 x 483 x 343 mm;
Weight 34.5 kg (each monoblock)