Balanced microphone on 8400 ?

Not sure at what photo you are looking. The “400” series has always had a pseudo-balanced mic input while the “600” has always had, in addition, a balanced mic input.

So how do those of us who purchased an 8400 connect our balanced microphones (PR 781 here) to our radio? I could hack together a cable with an inline transformer, but what is Flex recommending?

I understand the significant cost savings of using a common back panel, but I don't understand taking away the balanced input. I'm an audio engineer, and running unbalanced microphones in an RF environment can be a recipe for noise in the transmitted audio.

Why a transformer… ? I use an XLR-to-XLR isolation transformer with my 6400 and it sounds like my problem / solution may also apply to the 8000-series. But to support Neil N3DF: I cannot see why a 781 would need a transfomer.

Here is my longwinded explanation why I needed isolation transfomers; it may help someone else (but not if they use a Heil 781 by itself):

The problem (IMHO) lies with Flex terminolgy: "pseudo-balanced". Flex says they equalized and treated the two mic-input traces carefully, but in the end (when they hit the ADC and digitize) one side of the mic is grounded.

This is OK if you use a dynamic mic, by itself. It's a coil, right, and is quite happy if one end (or the other) is grounded, and there's signal on the opposite side.

My problem arose when I added active devices: may you add an XLR equalizer… in my case, I added a distribution-amp to feed one dynamic mic to several radios. It is key to understand that active outputs don't like being grounded 😯😫

My distribution amp uses + and - voltage-rails internally, and (with servo-feedback) outputs the bi-polar, differential driven signals directly. without coupling. Shorting one side of these active-outputs to ground inside my Flex was deeply unhappy (buzz, hum, but no damage). Simply adding a coupling transformer made for the job (ART DTI was my choice) resolved all problems - active outputs are happy driving the "floating" input-side of the isolation transformer, and Flex is happy grounding one end of the output-side.

Summary: in my mind, the use of the word "balanced" means something different than how Flex used that word. And (again, IMHO) if there is to be a "balanced input" capable of accepting active-device inputs, then it must not be grounded! A transformer will do that nicely. Even using XLR, one must understand the signal-flow, connections, and intervening devices.