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.
The 4 possible settings are:
LOW – Lowest damping factor, good loudspeaker control, most natural sound.
MED – Better loudspeaker control, with some impact on sound quality
HI – Best loudspeaker control, with a little more impact on sound quality, but on speakers that need the control the sonic improvement is clear
MAX – Maximum damping factor, but sonic impact is noticeable
Fully balanced differential circuit – even single-ended signal produces balanced signal at output
Re-designed fully balanced differential input and driver stages for increased signal swing, bandwidth and stability
Zero global Negative Feedback
Shorter, faster feedback loop for greater tonal control without phase shift
Improved handling of loudspeaker loads for greater signal stability
The amplifier is unconditionally stable, without the need for capacitor compensation
Tube like JFET-type current source for lower sonic impact in single-ended mode
Lower impedance output stage for improved loudspeaker control
Dramatically increased interleaving and coupling in the balanced VTL proprietary Signature output transformer, for wider bandwidth and zero ringing
Variable user-adjustable DF feedback control to vary output impedance and damping factor for optimal matching to speaker load
Software microprocessor controlled
Auto Bias, Fault Sensing
Current in-rush limiting
Standby Mute function; with reduced tube current for increased tube life
225 watts per channel in tetrode; 140 watts per channel in triode
Uses eight EL34 or 6CA7 tubes per monoblock
Adjustable regulated screen supply for stable operating point; discrete regulated input and driver supply for greater signal resolution and tonality
Adjustable precision-regulated bias supply for greater signal resolution and noise rejection and improved isolation from mains supply variations; output operating point does not change with AC power fluctuations
Improved Autobias and fault sensing system to operate in fully balanced differential mode; amplifier is fully protected against output tube failure; no need for precision matching of output tubes
All premium Mundorf silver oil caps in signal path
Film bypass of power supply caps for greater HF resolution
Extruded aluminum front panel with luxurious, modern look – black and silver options available
Rigid construction and improved ventilation for lower operating temperature
Factory upgradeable from Series II