Hi,
Adumb Gilligan Concussion wrote:
An XLR connection, to my understanding, uses a differential output for noise immunity. That is, there is a "hot" and a "cold" signal, along with a ground. The hot and cold are simply negative reciprocals of one another.
Plus 48V phantom power is coming from HOT (that's where it got
it's name).
You already have the single "hot" signal as described above. The only thing you need to do now is generate the "cold" signal
from that to send down the other line. This can be done by using a simple, general-purpose op-amp in the inverting configuration used as a buffer. That is, a gain of -1.
Which would result in a system with quite a bad common mode noise
rejection... For balanced system, output impedances of drivers and
input impedances of receivers should be well matched. Also, ratio
of input/output impedance should be quite large (10000 for
example). So reasonable would be to use two opamps for drivers.
For high common noise rejection, precision of impedance matching
is more important then precision of gain matching. Actually,
having gain of 0 on one line and gain of 1 on other line will
still result in system with good CM noise elimination, assuming
that impedances are close enough, only signal will have 3db of
attenuation. Also, using high quality opamps would not hurt THD
performance.
Indrek
--
Indrek Rebane | Borthwick-Pignon
Electronics Engineer | Tartu Science Park
Phone: (+372) 7 302 641 | Riia 185, 51014 Tartu
Fax: (+372) 7 383 041 | Estonia
indrek@... | www.bps.co.ee
