• Registered: 2018-02-16
  • Posts: 11

Topic: How to connect FF800 to unbalanced inputs?

I have read several articles about how to connect balanced output to unbalanced input, and that it depends on the type of balanced circuit.

My question is, do I connect the TRS cold ring (XLR = pin 3) to ground / shield like recommended in the article below or do leave it floating?

The FF800 manual says it is a servo balanced output, and I have read this article about how to connect balanced servo outputs to unbalanced inputs:

https://www.presonus.com/learn/technica … unbalanced

"Another electronically balanced configuration uses what’s often called a “cross-coupled” or “servo” balanced circuit. This generally uses three op-amps and delivers the full voltage between pins 2 and 3, even with one of those outputs connected to ground, the same as when unbalancing a transformer output. This output-circuit configuration was designed to emulate the effect of a transformer, and while it’s far less expensive than a good transformer, it requires a few more parts than a simple op-amp inverter. When connecting this type of output circuit to an unbalanced input, pin 3 should always be grounded. This effectively puts the two legs of the output circuit in series. By grounding pin 3, the full signal voltage, rather than half, will be seen by an unbalanced input connected to pin 2 and ground."

Best regards,

Rendboell

  • Registered: 2018-02-16
  • Posts: 11

Re: How to connect FF800 to unbalanced inputs?

After further reading in the FF800 manual, I found the answer:

Connect the TRS cold ring to ground / shield / sleeve (XLR connect pin 3 to pin 1).

I believe you should connect TRS cold to ground at the end of the cable (input to unbalanced), so you keep some noise reduction / Common Mode Rejection Ratio (CMRR)?

If I understand this topic correctly, CMRR in this configuration is 30 dB, while 60 dB in a fully balanced setup.

FF800 manual:

"The stereo 1/4" TRS jacks of the analog inputs and outputs are wired according to international standards:

Tip = + (hot) Ring = – (cold) Sleeve = GND

The servo balanced input and output circuitry allows to use monaural TS jacks (unbalanced) with no loss in level. This is the same as when using a TRS-jack with ring connected to ground."

Best regards

Rendboell