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-   -   What's the advantage of having a high (+-200R) output impedance? (http://www.diyaudio.com/forums/digital-source/27770-whats-advantage-having-high-200r-output-impedance.html)

Bricolo 7th February 2004 11:28 PM

What's the advantage of having a high (+-200R) output impedance?
 
A hundred of ohms seems to be a typical output impedance for a cd player, but why?

Isn't a low output impedance better?

And this impedance isn't even due to the I/V itself, but by adding series resistors in the signal. Wha'ts the need for this?

tiroth 7th February 2004 11:31 PM

It prevents oscillation of the output stage.

Pedja 7th February 2004 11:35 PM

CDP output stages almost always use feedback. Such stages are usually not stable on the capacitive loads. Series resistor decouples this load. Other than this resistor, output impedance is often notably under 1 Ohm. In the absolute terms, output impedance is not in any specific relation with the sound qualities.

Pedja

Bricolo 7th February 2004 11:39 PM

capacitive load? are you refering to the interconnects?

Pedja 7th February 2004 11:41 PM

To the interconnects and the (pre)amp's input.

Bricolo 7th February 2004 11:56 PM

can some pF cause problems for an opamp output stage?

Pedja 8th February 2004 12:08 AM

Depends on the actual opamp used. Some could drive a few nF, some will have problems even with a 10pF (mainly current feedback ones). Datasheets usually offer good info about this.

Pedja

Cobra2 8th February 2004 12:34 AM

It also protects the op-amp....for preventing them shortcircuit if output-wires become damaged...

Arne K

Tube_Dude 8th February 2004 12:36 AM

Re: What's the advantage of having a high (+-200R) output impedance?
 
Quote:

Originally posted by Bricolo
A hundred of ohms seems to be a typical output impedance for a cd player, but why?

Isn't a low output impedance better?

But a hundred ohms output inpedance...is a low output impedance!!!;)

Specialy feeding a pre amp or a power amp.

Pedja 8th February 2004 12:56 AM

Quote:

Originally posted by Cobra2
It also protects the op-amp....for preventing them shortcircuit if output-wires become damaged...
Yes, this might be the reason as well, though the opamps without short circuit current limiting are rather scarce these days.

Pedja


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