MB-185 Series III Balanced Signature Amplifier

MB-185 Series III Balanced Signature Amplifier
MB-185 Series III Balanced Signature Amplifier
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 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 an 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:
1. LOW -- Lowest damping factor, good loudspeaker control, most natural sound.
2. MED -- Better loudspeaker control, with some impact on sound quality
VTL MB-450 Series III Signature Monoblock Data Sheet
P. 1
3. HI -- Best loudspeaker control, with a little more impact on sound quality, but on speakers that need the
control the sonic improvement is clear
4. MAX -- Maximum damping factor, but sonic impact is noticeable
Feature List:
1. Fully balanced differential circuit –
even single-ended signal produces
balanced signal at output
2. Re-designed fully balanced differential
input and driver stages for increased
signal swing, bandwidth and stability
3. Zero global Negative Feedback
4. Shorter, faster feedback loop for
greater tonal control without phase
5. Improved handling of loudspeaker
loads for greater signal stability.
6. The amplifier is unconditionally stable,
without the need for capacitor
7. Tube like JFET-type current source for
lower sonic impact in single-ended
8. Lower impedance output stage for
improved loudspeaker control
9. Dramatically increased interleaving
and coupling in the balanced VTL
proprietary Signature output
transformer, for wider bandwidth and
zero ringing
10. Variable user-adjustable DF feedback
control to vary output impedance and
damping factor for optimal matching to
speaker load
11. Software microprocessor controlled
• Tetrode/Triode Switchable
• Auto Bias, Fault Sensing
• Current in-rush limiting
• Standby Mute function; with
reduced tube current for increased
tube life
VTL MB-450 Series III Signature Monoblock Data Sheet
12. 225 watts per channel in tetrode; 140
watts per channel in triode
13. Uses eight EL34 or 6CA7 tubes per
14. Adjustable regulated screen supply for
stable operating point; discrete
regulated input and driver supply for
greater signal resolution and tonality
15. 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
16. 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
17. All premium Mundorf silver oil caps in
signal path
18. Film bypass of power supply caps for
greater HF resolution
19. Extruded aluminum front panel with
luxurious, modern look – black and
silver options available
20. Rack mountable
21. Rigid construction and improved
ventilation for lower operating
22. Factory upgradeable from Series II
P. 2
MB-185 Series III Signature Monoblock Data Specification
Vacuum Tube Complement
Output Power
8 x EL34 or 6CA7, 1 x 12AT7, 1 x
Tetrode = 225 watts
Triode = 140 Watts
20 Hz – 20 kHz <3% THD
Into 5 ohms
Input Sensitivity
Variable between 1-2V, depending upon
DF setting
Input Impedance
Load setting
45K Ohms
5 ohms
Optimum Load Range
4 - 8 ohms
S/N Ratio @ 200 W Tetrode
S/N Ratio @ 140 W Triode
Power Consumption
-90dB, 120 Hz
Primary Mains Fuse Rating
Input Fuse
Logic Fuse
B+ Fuse Rating
Idle = 270 W
Full Power = 550 W
100/120V = 12A Ceramic Slo Blo
220/ 240V = 6A Ceramic Slo Blo
100/120V = 1A Ceramic Slo Blo
220/240V = 1A Ceramic Slo Blo
100/120V = 1A Ceramic Slo Blo
220/240V = 1A Ceramic Slo Blo
Plate Fuse -- 1.5A fast acting 600V
Screen Fuse – 0.75A fast acting 600V
W = 18.5 inches (47cm), D = 18 inches
(45.7cm), H =9 inches (23 cm)
85 lbs (38.5Kg) per monoblock unpacked
100 lbs (45.4 Kg) packed
VTL MB-185 Series III Signature Monoblock Data Sheet
P. 3
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