Reply to thread

Message

<blockquote data-quote="joetama" data-source="post: 4421232" data-attributes="member: 564641">Low Z out high Z in gives you a more true voltage follower circuit vs current follower. As the Z of the input device approaches being equal to the source device the source device has to supply more current than it would if the input device had a high impedance. The higher the current the more drain on the output circuit causing it to be less exact and increases the effects of inductance and capacitance on the line.This helps keep resonances low and helps reject other noise.It&#039;s fully JFET on the input which gives them the ability to generate such a high input impedance. I know there are pre-amps out there with 22k or 120k inputs. But, usually they are that high because they are sacrificing something else. Plus since the inputs are JFET it doesn&#039;t really matter since the voltage load across the input is usually very small while keeping a high ratio over the Vd at the outputs.&nbsp; Plus, I believe that the input is a differential input so even if noise was generated from the impedance crossover it would be filtered at the differentiator. I assume it is designed this way because with FETS you can&#039;t cheat and just invert the input with a capacitor or diode. Usually a pure FET design doesn&#039;t have many capacitors or anything else in the circuit path and Moon is known for the super short circuit paths.Anyway, with the fully balanced output MOS-FETS the output impedance can be 50 Ohms. So input into an amplifier with a high impedance input and you preserve the signal the best possible way.</blockquote>

[QUOTE="joetama, post: 4421232, member: 564641"] Low Z out high Z in gives you a more true voltage follower circuit vs current follower. As the Z of the input device approaches being equal to the source device the source device has to supply more current than it would if the input device had a high impedance. The higher the current the more drain on the output circuit causing it to be less exact and increases the effects of inductance and capacitance on the line. This helps keep resonances low and helps reject other noise. It's fully JFET on the input which gives them the ability to generate such a high input impedance. I know there are pre-amps out there with 22k or 120k inputs. But, usually they are that high because they are sacrificing something else. Plus since the inputs are JFET it doesn't really matter since the voltage load across the input is usually very small while keeping a high ratio over the Vd at the outputs. Plus, I believe that the input is a differential input so even if noise was generated from the impedance crossover it would be filtered at the differentiator. I assume it is designed this way because with FETS you can't cheat and just invert the input with a capacitor or diode. Usually a pure FET design doesn't have many capacitors or anything else in the circuit path and Moon is known for the super short circuit paths. Anyway, with the fully balanced output MOS-FETS the output impedance can be 50 Ohms. So input into an amplifier with a high impedance input and you preserve the signal the best possible way. [/QUOTE]

Verification