What goes into these most musically satisfying devices?

The Right Device for the job.

A power amplifier really has two distinctly different functions. First, an amplifier gain stage must increase the amplitude of the input signal by a factor of about forty. The distortion characteristics of the amplifier are dominated by this stage. More important than the total amount of distortion of an audio circuit is the character of the distortion. Odd-order harmonic distortion products are amusical, whereas even-order distortion products are part of the natural overtones of the musical instruments. FETs have been selected for voltage gain, because, like tubes, and unlike bi-polar transistors, they produce almost no strident odd-order harmonic distortion.

The high amplitude signal produced by the voltage gain stage must then be efficiently coupled to the loudspeaker system to assure the power and control needed to produce a musically accurate response.The degree of control is determined by the output impedance of the amplifier. Generally, the lower, the better. Bi-polar devices have been specified for the output stages of these amplifiers. The output stage produces virtually no distortion, and the bi-polar transistor offers about 1/4th the output impedance of a MOSFET, resulting in better control. This is most noticeable in faster, more solid bass response.

Minimal Negative Feedback.

Negative feedback is an engineering technique used to reduce measured distortion, and to diminish dependence of circuit performance on each individual part. While feedback does achieve these goals, it also introduces aberrations in the transient response characteristics of the circuit. By designing a highly linear circuit, and by specifying parts of high quality and precise tolerance, we are able to design amplifiers with less than 1/1000th the feedback of conventional designs.

Carefully Designed DC Power Supplies.

DC power supplies are an inseparable part of the audio signal path, and require as much care in design as the audio circuits. An ideal power supply would have zero ac impedance at all audio frequencies, so that the power supply voltage could not fluctuate with the audio signal. In conrad-johnson solid-state amplifiers, DC voltages are supplied to the critical voltage gain stage by discrete dc voltage regulators designed for vanishingly low impedance even at high audio frequencies. These regulators prevent the high current demands of the output stage from interacting with the gain stage, eliminating a major source of blurring of transients. The output stage draws its dc supply from a reservoir made from special electrolytic capacitors designed for high-frequency applications. A massive, over-sized power transformer assures that the output stage will never be starved for current.

Top Quality Parts.

These new amplifiers maintain the unmatched standard of parts quality for which conrad-johnson is internationally known. Audio circuit capacitors are polystyrene selected because they have less than 1/200th the transient blurring dielectric absorption of electrolytic capacitors. All resistors are low noise, precision metal foil and metal film types. Even the individually machined gold-plated input connectors, and premium quality machined output posts have been selected on the basis of their musical performance.

Specifications

MF5600 Amplifier

Output:



• MF5600: 5 x 120 watts per channel from 20 Hz to 20kHz at no more than 1% THD or IMD

  Frequency response: 20 Hz to 20 KHz +/1 dB
  Hum and noise: more than 100 dB below rated output
  Input Impedance: 100 KOhms

  Dimensions:
  

• MF5600: 16D x 19W x 8H inches

  Total Weight:
  

• MF5600: 59 lbs.