Following the footstep of the MB-450 Series III, the MB-185 Series III Signature monoblock has gone through the same technological improvements as its bigger brother. The upgrade to the Series III platform is extensive with a complete rework of the signal path and new features added while retaining all the user friendliness of the previous model such as automatic tube biasing and comprehensive fault sensing.
Upgrades include a fully balanced differential input stage driving a differential phase splitter and a lower impedance push-pull output stage. Also new is a shorter, faster and fully balanced negative feedback loop, with zero global negative feedback. The negative feedback loop completely eliminates ringing and requires no capacitor compensation to maintain critical phase integrity and information. The result is an amplifier that remains stable even under the most demanding loads.
Another significant change to the MB-185 is the switch to EL-34 tubes. Long admired for their rich, natural and open sound, the EL-34s bring a distinctive new sonic signature to the amplifier that emphasizes the integration and inner details of music. The output transformer has been completely redesigned and carefully matched to complement the midrange purity and quick, taut bass of EL34s.
There is also a new user adjustable Damping Factor Feedback control that allows the user to adjust the amplifier’s output impedance by varying the amount of negative feedback. Impedance can now be precisely set to suit the listener’s taste, and to improve control of the loudspeaker loads to deliver best performance.
Specifications and Features:
- Vacuum Tube Complement: 8 x EL34 or 6CA7, 1 x 12AT7, 1 x 12BH7
- Output Power:
- Tetrode = 225 watts
- Triode = 140 Watts
- 20Hz ‐ 20kHz <2.5% THD: Into 5 ohms
- Input Sensitivity: Variable between 1-2V, depending upon DF setting
- Input Impedance: 45K Ohms
- Load setting: 5 ohms
- Optimum Load Range: 4 - 8 ohms
- S/N Ratio: 225W Tetrode & 140W Triode: -90dB, 120Hz
- Power Consumption:
- Idle = 270 W
- Full Power = 550 W
- Primary mains fuse rating: 100/120V = 12A Ceramic Slo Blo, 220/240V = 6A Ceramic Slo Blo
- Logic fuse: 100/120V = 1A Ceramic Slo Blo, 220/240V = 1A Ceramic Slo Blo
- Input fuse: 100/120V = 1A Ceramic Slo Blo, 220/240V = 1A Ceramic Slo Blo
- B+ fuse rating: Plate Fuse – 1.5A fast acting 600V, Screen Fuse – 0.75A fast acting 600V
- Dimensions W x D x H: 18.5 x 18 x 9 inches (47 x 45.7 x 23 cm)
- Weight: 85lbs (38.5kg) per monoblock unpacked, 100lbs (45.4kg) packed