Belles MB-01 Brochure

Substance

The key to accurate audio reproduction is the ability to resolve detail. To that end, David Belles has designed his first
class A amplifier in 30 years. Everyone knows that class A biased amplifiers represent the pinnacle of what is possi­ble in amplifier performance. However, designing and building a class A amplifier is no easy task. The first amplifier
that Dave Belles designed more than 30 years ago was an class A amplifier known as the Belles A. Since that time,
Dave Belles has learned what it takes to produce a truly great class A designed amplifier.

Class A design requires attention to tolerances, heat needs to be dissipated, power supplies need to be sufficient in
order to produce an amplifier that does not compromise performance. The amplifier's power rating needed to be care­fully selected in order to produce a unit that would drive most speakers at sound pressure levels that are satisfactory
to most users.

Class A design is the best, regardless of what anyone would try to tell you. Class B or AB designs use complimentary
output transistors biased on the threshold of current conduction. The design uses one polarity of transistors to supply
power to the loudspeaker load from the positive rail supply and another opposite polarity to supply power to the loud­speaker from the negative supply rail.

Imagine that the amplified signal is in the form of a sine wave, where the positive supply rail transistors supplies the
upper (or positive) portion of the wave, and the negative supply rail transistors supplies the lower (or negative) portion
of the wave. Class B or AB design amplifier's transition from the positive to the negative portion of the sine wave is
never perfect. This imperfect crossover from positive to negative creates a crossover notch, leading to crossover dis­tortion. In B designs, another distortion is also created in the form of power supply modulation due to various signal
power level demands.

Switching type amplifiers have other deficiencies. Switching amplifiers take sample portions of the signal and recon­struct the wave at the amplifier's output using filters. This means that signal information is missing and the amplified
signal is interpolated. The result is a lack of accuracy, detail and warmth. Class A designs do not suffer from any of
the above deficiencies.

Substantial

From the quality of the circuit board components, to the heft of the chassis construction, the Belles MA-01 has been
built to be a substantial audio component.The front panel is made of 1 inch (25.5mm) thick anodized aluminum. The
top and bottom covers are .25 inch (6.35mm) anodized aluminum. A .125 inch (3.2mm) anodized aluminum rear
panel and massive anodized aluminum heat sinks complete the impressive chassis. The power supply consists of a
1000 volt-ampere toroidal power transformer with 234,000 microfarads of filtering capacitors. The output transistors
consist of a bank of 20 mosfet power transistors. The Belles MB-01 is stable even with a 1.0 ohm load.

All other components in the MB-01 amplifier are the finest: 1% metal film resistors, polypropylene capacitors, glass
epoxy circuit board, oxygen free copper wire, oxygen free cast copper speaker binding post, gold plated oxygen free
copper input connector. Also included is a on soft start power turn on circuit to eliminate power turn on surge tran­sients and component failures.

Belles MB-01 Monoblock Amplifier

Specifications

Frequency Response:...........................................................0.2 to 100,000 Hz

Power Rating: ........................................................................75 watts of pure class A power

.................................................................................................85 watts peak into 8 ohms

.................................................................................................161 watts peak into 4 ohms

.................................................................................................287 watts peak into 2 ohms

................................................................................................458 watts peak into 1 ohm

Distortion: ..............................................................................IM and THD less than .01%

Damping factor:.....................................................................over 5000 into 8 ohms

Peak current:..........................................................................80 amperes

Input Impedance: ...................................................................50,000 ohms unbalanced

.................................................................................................and 100,000 ohms CT balanced

Input sensitivity:....................................................................1.17 for 75 watts

Gain: .......................................................................................21 voltage ratio or 26.44 dB

Inputs:.....................................................................................1 unbalanced RCA connector

.................................................................................................or 1 XLR balanced connector

Hum and Noise:.....................................................................over 100 dB

Dimensions:...........................................................................17 "(432.8mm) wide,

.................................................................................................10.5"(266.7mm) high,

.................................................................................................13.5"(342.9mm) deep

Power Requirements:............................................................120 VAC 8.0 A, 240 VAC 5.0 A

Power Modules Inc. 479 East Street Pittsford, N.Y. 14534 [phone]