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Post by charleyphogg on Jan 14, 2008 8:48:01 GMT
In general. Or when/how should you look for possible impedence mismatches?
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Deleted
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Post by Deleted on Jan 14, 2008 9:59:54 GMT
charleyphogg A simple example of matching would be with a video buffer stage. If the stage has a gain of 2 (normally non inverting) and you connected to the TV (etc) with a length of 75 ohm cable,you would normally have a resistor of approximately 75 ohms in series with the output device, and at the TV end of the coaxial cable you would terminate the cable with another 75 ohm resistor. Thus the TV would then see 1/2 of the 2x amplified output voltage, and the other 1/2 of the voltage would be dropped across the series 75 ohm resistor. This means that if the input to the buffer was 1V (peak to peak) AC, then the TV would see the same value of 1V AC (peak to peak). I used video as an example, because matching is far more critical to ensure a picture without reflections (ghosting) Impedance matching with audio is not normally critical with domestic equipment, but is essential for distribution in a Sound Studio, where cable lengths are much longer and integrity of the signal more important. Impedance matching is often more relevant when an amplifier is used to drive headphones. Much headphone equipment these days (including Green Solo) uses a series 120 ohm resistor at the device's output (I.E.C. standard value), to get the best performance from headphones that comply with this standard. There are other instances of impedance matching such as in SPDIF transmission between a CD player and a DAC, and also a degree of matching is employed with source devices, preamplifiers and amplifiers. There is also purpose built buffer equipment from some manufacturers to help ensure better SQ between a less sophisticated source and the next stage. In this instance, their main purpose is to isolate the source device from the interconnect's capacitance with minimal loading of the source, but present a good low impedance drive to the interconnect and succeeding stage. SandyK
(This is meant only as a simple general guide.)
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Post by charleyphogg on Jan 15, 2008 0:26:30 GMT
Thanks for the explanation Sandy.
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