CAPACITORS AND MECHANICAL DIODES.
Capacitors are a necessary evil in amplifier circuits, although their elimination, irrespective of value or type, seems to instantly improve the sonic quality of amplifier circuits.
They store energy at various frequencies and release this energy over a period of finite time to smear, add grain or texture and a form of hardness to the overall sound, which in earlier times was reported as the 'transistor sound'.
In our preamplifier audio and regulator circuits excluding the DC servos and DC protection circuits, apart from the RIAA equalisation capacitors (1% polystyrene) there are two levels of power supply capacitor types; a large value computer grade electrolytic, bypassed with a smaller electrolytic just before the regulation circuits.
Most audiophiles are familiar with the 'mechanical diode' concept pioneered by the French in their turntable design. This concept overcomes the problem of energy evacuation from the turntable by using materials of different composition to effectively remove vibrations away from the system and channel them to earth. We employ this concept as a matter of course in all our amplifiers to evacuate the vibration of the critical low-level amplification stages on our printed circuit boards.
Be removing the transformers from our preamplifier mainframes and isolating them in a separate power supply, we remove this source of potential microphonic vibrations from the sensitive phono stages.
Our power amplifiers use an isolated shelf onto which the massive power transformers are mounted and which are physically connected to the P.C. board using 40mm of flexible wiring. The power transistors support the complete printed circuit board with one single standoff connecting the base of the amplifier to the P.C. board just beneath the large computer grade capacitors used for the primary filtering.
THE ELECTRICAL EQUIVALENT OF THE 'MECHANICAL DIODE'.
Amplifiers are 'dynamic' circuits which utilise resistors, transistors, copper tracks, capacitors and controls which all have their own unique fundamental resonant frequencies and require an electrical equivalent of the mechanical diode concept to evacuate all these extraneous resonances from the system.
This is in addition to the signals which are encountered by the amplifier circuits and resonate through the regulated power supply onto the primary filtering and back to the amplifier circuits as a form of out-of-phase information.
There are no means of electrically testing for these phenomenon because of the resolution of modern test equipment, although through extensive listening tests we are able to reduce these electronic resonances which correlate to an improvement in transparency, fine detailing and in particular the development of a panoramic sound-stage with excellent depth.
BALANCED INPUTS.
All MAS phone and power amplifier inputs utilise a symmetrical differential input which essentially reflects a balanced input as the impedance from the input to the 'non-inverting differential pair' and from the 'inverting differential pair' to GND is identical.
This is a result of using a circuit topology which is the closest to having the benefits of using balanced inputs without the drawbacks.
The reason we have resisted following the trend of using professional concepts in domestic amplification is that to create a fully balance input/output amplifier requires the use of an extra stage of gain or 'summin amplifier' with sufficient output current to drive a 600 Ohm following input impedance instead of the normal 10,000 Ohms.
In the case of our preamplifiers, this would translate to the signal going through twelve transistors stages instead of six from the phono to the preamplifier output and unnecessary increase in the output idle current.