User manual HAFLER SERIES 9505

[. . . ] 9505 Installation & Operation ® ® an tr va no s USA IN T E HE MAD PROFESSIONAL POWER AMPLIFIER AMPL NOTICE - IMPORTANT SAFETY INFORMATION CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN ! The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user to the presence of uninsulated "dangerous voltage" within the product's enclosure, that may be of sufficient magnitude to constitute a risk of electric shock to persons. The exclamation point within an equilateral triangle is intended to alert the user of the presence of important operating and maintenance (servicing) instructions in the literature accompanying the appliance. It is important that the blades of the equipment's plug be able to fully insert into the mating receptacle. Never remove the round grounding pin on the plug in an attempt to mate to a two wire ungrounded receptacle: use a grounding adaptor with the grounding tab or wire suitably connected to earth ground. [. . . ] The output stage is further refined into a trans-impedance stage (current-to-voltage converter), to achieve extremely short loop (fast) negative feedback. The output stage is driven cooperatively by a transconductance stage (voltage-to-current converter). The 9505 is the most sophisticated amplifier we have yet developed utilizing the basic trans·nova principle. And, although the measured specifications are very good, the numbers do not describe the realistic sound of the amplifiers. CIRCUIT IMPLEMENTATION Earlier models of amplifiers we have offered using the trans·nova topology have earned the reputation for clean, natural sounding reproduction. A conservative, purist design approach was used to avoid compromising the desirable characteristics of the trans·nova circuits. Circuit innovation was not prevented by this conservatism; as is evident in the discoveries which resulted in development of the DIAMOND circuitry to be discussed shortly, and the novel balanced input system. Many "balanced" amplifiers are merely conventional unbalanced designs with a Balanced-to-Unbalanced converter (usually IC op-amp based) preceding the power amplifier. Each (+) and (­) input port has been buffered to allow direct signal access to the differential amplifier, without conversion to unbalanced form. Deactivating the Balanced Mode is accomplished via a rear panel switch that grounds the (­) inputs, effectively converting the amplifier to unbalanced operation. This circuit configuration results in excellent front end headroom and extremely low intermodulation effects. The ultra low noise characteristic of the JFETs virtually eliminates noise "mixing" (intermodulation) with the music signal, reducing discordant product frequencies known as "noise grain" or "noise fuzz. " A servo integrator has been employed to establish minimal DC offset. This circuit monitors the DC offset at the output of the amplifier, and injects an equal but opposite DC voltage into the (+) port of the differential input, thereby cancelling the offset. This method eliminates the need for a sonically degrading electrolytic capacitor in the audio path, and provides superior subsonic frequency response. ­ 13 ­ The final output stage utilizes lateral MOSFETs; four pairs are used for each channel in the 9505. These devices, unlike conventional bipolar transistors do not exhibit "thermal runaway. " Thermal runaway is a phenomenon whereby a transistor heats up as it draws more current, which causes it to get hotter, and conduct more current, and so on until the device self destructs. Since the MOSFETs are inherently self protecting, no sonically degrading, complex circuitry is required to monitor and protect the devices. The lateral MOSFETs also have a linear input to output transfer function. Their connection in circuits and their operating characteristics are very similar to vacuum tubes, which is perhaps responsible for their widely recognized sonic trait of being "musical" and non-fatiguing. Operation of the transconductance stage is a major factor in the reproduction quality of the amplifier. The number of MOSFETs used at the output stage of the 9505 imposes sufficient capacitive load on the transconductance stage that if a conventional Class A stage were used (having intrinsically a 2:1 limit on peak-to-quiescent current) it would begin to show "stress" at the higher audio frequencies. The newly perfected DIAMOND (Dynamically Invariant AMplification Optimized Nodal Drive [patent pending]) driver stage satisfies the current headroom requirement by smoothly and continuously varying the current transfer ratios of the two transconductance paths, under the control of the signal current itself. This implementation allows the current transfer ratio of one path to be smoothly and continuously reduced to zero while the other is smoothly and continuously increased by a factor of two. What is remarkably new here is that when this normally-limiting 2:1 value is reached there is now about 14dB of additional, perfectly linear current headroom left to drive the MOSFETs! [. . . ] SEGUIRE LE ISTRUZIONI Tuttle le istruzioni operative e di funzionamento devono essere seguite. TEMPERATURA L'apparato deve essere mantenuto lontano da tuttle le zone ad alta temperature, termosifoni, termoconvettori, stufe e forni, caminetti ed altro. VENTILAZIONE L'apparato deve essere posizionato in aree convenienti per una corretta ventilazione. Prestare attenzione che sia consentita circolazione d'aria attorno e dentro il cabinet. [. . . ]