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Simaudio Technical Education
MOON Amplification Technologies 		Updated: February 10, 2010    

 
MOON Bipolar Transistors
 
Transistors in an amplifier’s output stage perform what can be best described as electrical gain of the music signal. Higher quality transistors will yield an amplified signal with greater integrity. In addition, since each channel of an output stage uses numerous transistors, they must all be accurately matched to each other to maintain this integrity.

MOON amplifiers have always used bipolar transistors in their output stages for several significant reasons. When compared to other types of amplification transistors, bipolars offer:
  • Wider bandwidth
  • Lower distortion
  • Excellent reliability and a longer life span
  • High Efficiency
  • High resistance to ESD (electrostatic discharge)

We have managed to have, at great expense, bipolar transistors manufactured to our own high standards and specific requirements. When compared to more readily available high quality bipolars for use in audio amplifiers, MOON Bipolars offer the following advantages:
  • Unprecedented gain linearity
  • A green component containing no lead
  • Lower noise floor
  • Even wider bandwidth
  • Improved bass response
  • Greater signal integrity
  • Even greater reliability at higher output levels
  • A more consistent hFE (the DC current gain of a transistor) which allows for more accurate and easier matching of multiple Bipolars.
 

 
The exceptional gain linearity of MOON Bipolars is very significant in the sense that it results in many of these aforementioned advantages. To illustrate the significant effect of this gain linearity when compared to a quality bipolar transistor found in a high-performance audio amplifier, refer to the figure below which shows the difference in DC current gain as a function of the transistor’s output current:

 

 
Optimal sonic performance is always achieved
regardless of the amplifier’s output level.

 

 
DC–Coupled Amplifier Design
 
Without the blocking capacitors at the amplifier’s input, sound quality is improved as the phase-shift caused by these capacitors is eliminated. Frequency response in the bass region approaches 0Hz. As well, by removing all capacitors from the direct audio signal path, ultimate soundstage focus is attained with less "smear' or "blur".

 

 
The black frequency response curve in the figure below is virtually flat throughout and beyond the entire audible range as a result of the DC-Coupled circuit employed on our MOON amplifiers. Conversely, the red frequency response curve of a traditional AC-Coupled amplifier design is far from perfect, both low and high frequencies in the audible range are noticeably diminished:

 

 
Deeper, more accurate and articulate bass ... You will clearly distinguish between a double-bass and an electric bass in a heartbeat.

 

 
Toroidal Transformers with a Very Tight Regulation Factor
 
A power supply transformer with a tight regulation (low) factor assures that power into more difficult speaker loads will be delivered closer to the theoretical ideal. These transformers are significantly more expensive, but are the only way to assure stability and consequently excellent sound quality under all conditions.

 

 
The three response curves in the figure below demonstrate (i) a theoretically perfect transformer regulation factor of 0% (green) whereby voltage remains stable regardless of the current draw, (ii) a remarkably low regulation factor of 3% (black) found in MOON amplifiers, where the voltage drops slightly as the current draw increases and (iii) a typical regulation factor of 10% (red) whereby, as the current draw increases, power supply voltage drops significantly, as found in most competing amplifier designs:

 

 
Powerful musical passages are faithfully and
thoroughly reproduced in an effortless manner.

 

 
High Damping Factor
 
The output section of all MOON power amplifiers possess a high damping factor that ensures an excellent “grip” on woofer cone motion. This reduces overshoot and unwanted oscillations. A high damping factor also greatly improves the immunity to variations in both the quality and the length of speaker cables used.

 

 
A great deal more energy from a power amplifier is required to reproduce musical information below 400Hz. Amplifiers with a low damping factor (and higher output impedance) have to work harder to produce this energy:

 

 
The majority of available power amplifiers possess a damping factor in the range of 200 (red), as shown in the figure below. MOON amplifiers operate with very low output impedances (typically <0.01 ohms), therefore yielding a damping factor greater than 800 in the all-important sub-400Hz range:

 

 
Significantly better dynamics result in a much more powerful and
authoritative bottom-end ... The immense energy of a full
symphony orchestra comes to life in your own home.

 

 
 Advanced Renaissance Circuitry         (Simaudio Ltd. Proprietary Technology)
 
Introduced in 1998 with the MOON W-5 Power Amplifier, this circuit topology features a no overall feedback design, also known as "Zero Global Feedback". By eliminating the need for signal correction, amplifier speed is greatly increased. Simaudio amplification designs allows for superb performance into difficult loads, which further improves sound quality.

 

 
Power amplifiers employing feedback have additional circuitry (feedback loop in red) which takes a sample of the audio signal from the amplifier's output stage, applying it as negative feedback to the gain stage of the amplifier as shown above. The sole purpose being to reduce the amount of Total Harmonic Distortion (THD) the more feedback used, the greater the reduction in the amount of measurable distortion.

Benefits include:
  • real-time amplification.
  • more accurate musical reproduction w.r.t tonality - no colorations.
  • non-existent intermodulation distortion (IM).
  • elimination of common phase errors
  • With this circuit topology, the speaker cannot send back its counter-reaction to the amplifier after a musical impulse. This normally leads to a reduction in clarity of the music, a lack of tonal accuracy and the feeling of the live performance being lost.
  • Improved dynamic range.
  • more dynamic and at ease with virtually any known speaker load, short signal paths, very little signal resistance and degradation.
  • An amplifier which is much less affected by a loudspeaker's non-linear electro-mechanical properties.

Better transparency ... The realistic separation and space between instruments in complex musical passages results in the recovery of the faintest of musical notes.

 

 
 Lynx Circuitry         (Simaudio Ltd. Proprietary Technology)
 
Introduced in 2005 with the MOON W-8, and later on in both the MOON W-7, MOON W-7M and 700i, the main difference from the "Advanced Renaissance Circuit" is power supply distribution; a more accurate delivery for the individual active devices in the amplification circuit is realized. This is achieved by   i) the very close proximity of the gain circuit to output circuits and   ii) decoupling the output stage transistors from each other.

Benefits when compared to the Advanced Renaissance circuit:
  • Even faster.
  • More accurate reproduction.
  • More dynamic.
  • Larger output reserves.
  • Shorter signal path.