Q. If I have balanced TRS outs on my synth, do I NOT need a DI??

Or, am I just really confused?

So, I've been researching DIs lately, and trying to grasp things like "load", "high impedance", "impedance bridging", etc.

My prior knowledge was that DIs were used mainly to reduce noise by balancing the TS output, thereby helping to reduce noise out from the synth & make long cable runs possible.

Now, I get the impression that DIs are mainly there so that you can plug synths into Mic pre's, in which case you need the impedance bridging of a DI. In fact, I read that many DIs will actually INCREASE noise, which is contrary to what I've known.

So, I'm not supposed to make a direct balanced connection between synth and mic pre? I'm not supposed to think that a DI will help the noisy outputs of my RD700?

DIs perform two functions - balancing the instrument or line signal and reducing that signal to mic level. A balanced signal can still be line level. Plugged directly into a mic pre, a synth with a balanced output, like the JoMoX Sunsyn and presumably your Roland, would still need some kind of pad to reduce the volume, or you'll overload the pre. Some DIs are noisier than others. The Groove Tubes DITTOs I own hiss like two cats in a sack, which is a surprise, because the first one I used was considerably quieter. I've never heard undue noise from the Hamptone and Avalon DI/Mic Pres, so I reckon it's largely a question of components and engineering.

Thinking about it, I don't know how balancing would redress noise coming from the synth. As I understand it, common mode rejection would only work on noise introduced between a balanced source {a mic pre's output, eg} and destination {mixer channel}. If your RD700 is noisy, maybe there's a problem with your unit.

If I've got this wrong, and it wouldn't be the first time, please correct me.

The trs cables just make the synth noise cleaner!

Hey guys, thanks for the info.

Yeah, the more I think about it, the more I'm convinced that a balanced cable isn't the solution I'm looking for...

I'm gonna think a little more about the possibility of a problem with the RD700 itself. Hmm...

Thanks again

audio cables work like lowpass filters, even over short runs of a few feet. the quick experiment is to plug something like a lavalier mic which will connect directly into your preamp and then plug it in with a mic cable in between- the difference is dramatic! DI'ing an unbalanced signal is essential for long audio cable runs otherwise your instrument's signal will have significant, audible roll-off.

of course, these days some people just digitize to avoid long runs, but there are other uses and a number of in depth articles on the internet covering this perennial subject. DI boxes should not reduce the noise an instrument is generating on its own.

If your synth has balanced XLR outputs, the only reason you would need a DI is isolation. If connection creates a hum or buzz, a passive DI with a transformer will isolate the electrical connection between synth and PA. Ground lift alone does not always solve this.

Also just because a synth had balanced XLR does not mean that the opamp drivers on the balanced circuit is capable of driving long transmission lines.