Guest wrote:
Hi Dan, could you tell me what the output impedance of the DA10's XLR output is (I only need to know the value considering one output pin, for unbalanced operation)? I love my DA10, thanks a bunch!
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Regarding the output resistance for the XLR's:
There is 75Ohms in series to each XLR active pin. The circuit impedance is less then 1 Ohm, so why 75 Ohms in series? Long cables are capacitive load at "low frequencies" (into the many MHz). Active circuits driving long cables may oscillate at high frequencies. It is common practice to prevent such oscillations (which will be heard as distortions) by use of small series resistors.
For XLR's the load is most often very high (such as 100K, 10K or similar) so the series resistors do not cause attenuation. There are a few cases, mostly unbalanced, where the load is as low as 600Ohms, and the series resistance will cause some signal attenuation (1dB at 600Ohms).
At 10Kohms load, the loss is only about .12dB.
The output voltage of the XLR is very high (24dBu) so a 75Ohms is a good value - plenty of margin for stability (no oscillations) and not much loss.
Regarding the output resistance for the headphone:
With headphones, the parameters are different. The current for some headphones is very high, the load is not always capacitive... so one needs a strong driver with very low series resistance. The series impedance is 0.69 Ohms so that a 600 Ohm load will cause only 0.07dB loss.
Regards
Dan Lavry
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philodox - Ok, WTF? Does he actually state the output impedance anywhere here?