Connecting balanced outs to the PA..

[Hobo]

I posted this on another forum while this one was down but really wanted to hear from you all here!

 

I do lots of gigs. There's often trouble with ground loops / hum / noise. My sounds come from a mac running MainStage, out through a Focusrite USB 6. This has quarter inch outs which can be electronically balanced. My sound is much cleaner using the TRS balanced out.

 

So how do I best connect to a PA? I'd like to use TRS jacks but most gigs I'm presented with a DI box. Don't most DI's have unbalanced inputs? Therefore not taking advantage of my balanced out?

 

Should I go TRS jack to XLR and just remove the DI from the equation, or does that leave me susceptible to Phantom power ruining my sound card?

 

What's the accepted wisdom in this situation?

[ITGITC]

 

So how do I best connect to a PA? I'd like to use TRS jacks but most gigs I'm presented with a DI box. Don't most DI's have unbalanced inputs? Therefore not taking advantage of my balanced out?

 

The Radial ProD2 has unbalanced inputs. Specifications here

 

With short cables from your Focusrite USB6 to the DI, you should not have a problem with RFI.

 

The DI uncouples the Focusrite USB6 from the mixer. It also has a ground lift. This should alleviate your ground loops / hum / noise problems. The DI also terminates in a mic level output, which is what the sound tech prefers to see.

 

 

[MoodyBluesKeys]

I use a Radial ProD2, and my Kurzweil PC3 has balanced outputs. Even though the Radial 1/4" inputs are unbalanced, no problems seem to arise. Keyboard to Radial in, Radial 1/4" out to my K10 monitor, XLR balanced out to the FOH system, ground lift lifted. 20db pad in or out to meet the FOH sound person's level needs. No hum, no noise, only thing it doesn't cure is my playing ability.

 

I don't even carry any TS cables, all my cables are either TRS to TRS, TRS to XLR, or XLR to XLR. (except the cable for the guitar and bass guitar).

 

 

[JohnS77]

radial definitivelt make good stuffs. I use the JDI DUPLEX, not cheap. it is amazing and takes away all noises giving me a clean signal... again it is call RADIAL JDI DUPLEX.....

[JeffLearman]

You could try an ART DTI, which has balanced inputs, but not as good a transformer as the JDI. It doesn't attenuate the signal, though, which can be an issue. (The DTI has two channels. I don't know whether they make the same thing with one channel.)

 

When you use balanced outputs to balanced inputs, it's 6dB louder than to unbalanced inputs. Often that can fool us into thinking it sounds better, just because it's louder (louder nearly always sounds better).

 

You don't want to run direct without a DI, for the reasons you mentioned. Phantom power can be bad, and you're still subject to ground loops and other nasty business if everything isn't grounded properly.

 

I agree with folks above that for short runs, unbalanced is fine, and you'd be best with a good DI like Radial ProDI or JDI.

[Hobo]

Great, thanks, those JDI's sure look nice, will have to invest one day But if you have a balanced, noise free output, why would you need a DI at all? Apart from protection from phantom power, an isolator would do the same job?

 

 

[JeffLearman]

The ART DTI is an isolator, and as I said, you'd need an isolator or DI to avoid problems with phantom power or ground issues.

 

But you might also need a signal attenuator, which an isolator doesn't necessarily have. Line outputs are considerably hotter than mics, and the PA might not have enough pad to pull your signal down to a reasonable level. But if you find an isolator with a pad, you're golden.

 

BTW, an isolator with a pad is pretty much what a passive DI box is. The difference being things like thru connectors and whether the input is balanced or not. Some DIs might have balanced ins.

 

But I really doubt balanced/unbalanced is a big issue for short runs.

 

The JDI (or anything with Jensen transformers) is best, and the ProDI is almost as good and much more affordable. Just about anything else will use serviceable inexpensive transformers, which are fine, but not stellar.

[ITGITC]

But I really doubt balanced/unbalanced is a big issue for short runs.

I use Whirlwind Director DI boxes (2).

 

Looking at Whirlwind's site, they describe the Director, and this box, the Direct2-JT as having unbalanced inputs.

 

Indeed, this is a feature!

 

DIRECT2-JT LINK

 

Part number: DIRECT2-JT

 

The DIRECT2-JT is Whirlwind's premium Dual Direct box, built with Jensen transformers.

 

Perfect for converting unbalanced signals from stereo keyboards, acoustic guitar preamps, CD and tape players, computer sound cards, etc. when lowest noise and widest frequency response are required.

 

 

[Hobo]

But I want balanced inputs, don't I? As my output is balanced.. Or at least it can be, and when it is it's cleaner and louder.

 

Thanks for all the advice folks.

[J. Dan]

For $132 you could buy a Jensen balanced isolation transformer and put it in your own box with your choice of connectors (TRS in, XLR out).

 

CLONK

[Hobo]

Thanks Dan. I'm looking at these right now - Orchid Isolator

[mate stubb]

Again, balanced outputs don't generally provide practical help, for short runs. If you wrap your signal cable with a power cable, then yes, they could help. But the extra gain is not usually needed to connect to a PA, in fact it can be too much as already stated.

[Theo Verelst]

Balanced generally speaking would be for preventing hum and possibly rattle and other electro-magnetical couplings making your wires receive sources you don't want. By balancing, the two wires in your jack/xlr cables cancel out interference, and a balanced input will give 6dBV more signal at the mixers input when both cable parts are connected.

 

An extra inverter (at least) at the mixer input also creates a touch more distortion, and the "measured" signal at the balanced input can still give problems, and still the connected grounds on the two sides of the cable can interfere with the mixers perceived input signals. Also, there's a bit of unbalance in most coupling capacitors at possibly the mixers' input and your synth's balanced outputs, which creates some sort of "low boost" which is hard to get rid if unless it's a pro-mixing setup, unless you use sounds in your synth which anticipate this (al the time the same) effect.

 

Without disturbance, the noise floor can go down by going balanced (i.e. you get a little more dynamic range), but if that happens in practice is questionable, and considering how quiet most modern digital synths are at their outputs, probably it isn't needed live.

 

The transformers make the signal impedance difference, load the synth a bit difference, have near perfect balance, but, even the Jensens' will distort a bit (IMO audibly, but that for a lot of people is too much nitpicking I'm sure). What is a general issue is that the transformers give phase shift and a little less low frequencies, which can be an issue with players using the transients of their instrument conscientiously.

 

The separation the transformers give is perfect, and safe, and prevents ground loops which are always annoying. Driving the DI box balanced or not probably makes not all too much difference, but maybe a bit I don't know.

 

T.

[bourniplus]

But if you have a balanced, noise free output, why would you need a DI at all? Apart from protection from phantom power, an isolator would do the same job?

In some situations you might have a computer-ground-loop problem. I used to have this sometimes when running VSTs, and a D.I. takes care of it.

[JeffLearman]

But if you have a balanced, noise free output, why would you need a DI at all? Apart from protection from phantom power, an isolator would do the same job?

In some situations you might have a computer-ground-loop problem. I used to have this sometimes when running VSTs, and a D.I. takes care of it.

Right, but an isolator would solve that too.

 

But I want balanced inputs, don't I? As my output is balanced.. Or at least it can be, and when it is it's cleaner and louder.

Yes, but the difference is negligible.

 

Louder is a problem since line level signals are already too loud. DI boxes generally reduce the signal by 20dB in the transformer and have an additional pad switch for another (typically) 15dB cut.

 

The "cleaner" bit is correct but by a very small amount, one that would be very unlikely to be noticeable in a live application, and possibly not even in the studio.

 

My guess is that the sound would be better through a Jensen transformer with unbalanced input than any other transformer with a balanced input. Possible exception might be the Radial Pro transformers; who knows which is more significant: diff between Jensen and Radial xformers or balanced and unbalanced connections.