When connecting the Symphony I/O's balanced analog outputs to a device with unbalanced inputs - such as a vintage console or consumer electronics gear - the cable should be wired a certain way to ensure the best audio quality and lowest noise:
The Symphony I/O original module cards and MkII module cards:
- The outputs are electronically balanced to behave like transformers.
- So accordingly, one side (pin 3) of the output stage will need to be tied to ground when driving an unbalanced input.
Wiring should be done like example 5 or 6 in figure 4 of the Rane Note 110 article: https://www.ranecommercial.com/kb_article.php?article=2107
Also make sure you set the output level of each Symphony output driving an unbalanced load to -10dBv to prevent overloading the input circuitry and achieve the most optimal signal to noise ratio.