CD Player through DI

[benatkinson]

Just a quick problem.

 

At a future gig I have a cross fader that outputs 2x RCA and I need to feed it into a 8 channel DI box about 20m away.

 

Do I run a long phono cable striaght into the DI unit OR do I get a RCA to XLR connector and then run it down XLR wires into the DI.

 

Thanks, Ben

[MarkPAman]

Do I run a long phono cable straight into the DI unit

Second best

 

OR do I get a RCA to XLR connector and then run it down XLR wires into the DI.

No point

 

Better would be to get the distance to the DI box down as much as you can. Move the DI, move the DJ mixer or get another pair of DIs

 

Try your first option, you may get away with it. If not try one of mine. :o

[Bobbsy]

If you have to do a long, unbalanced run (i.e. phono lead) to your DI, then at least make sure you make up a quality pair of leads using screened cable, not the sort of bell-wire lead that most cheap phonos are made from.

 

However, for the cost of doing this, you'd probably come close to being able to spring for a couple of inexpensive passive DI boxes.

 

Basically, there are two reasons for using a DI box. First, and mainly for instruments like an electric guitar, they match impedence and levels making them suitable for the input on the mixer. Second, they take the unbalanced signal and convert it to balanced, making it FAR more resistant to electrical interference. If you want to know how this works, do some Googling and read up on "common mode rejection".

 

In the case of your CD player, levels and impedence are unlikely to be an issue...so the whole reason for doing this is to balance your signal. Since the stage is almost certainly an electrically noisy area, a long phono lead run to the DI box is undesireable. A screened lead will help, but is no substitute for balancing the signal right at the source. As MarkPAman says, there's no point in converting to an XLR connector unless you balance the signal as well.

 

Bob

[mal421]

Or get a DJ mixer with balanced outputs .

[Dave]

I would agree that a couple of DI boxes close to the DJ mixer is the best solution.

 

However, do remember that the DJ mixer will have low impedance outputs at a pretty high level. So using some phono-XLR leads may work just fine. With this approach, it might even be best to bypass the eight-way DI and go straight into the PA mixer.

 

Whilst a balanced connection obviously gives a degree of noise rejection, it's not the case that you will always get noise if the signal is unbalanced. I've run unbalanced signals tens of metres without problems. Years ago, I used to use jack-male XLR leads to send the output of synths and keyboards down the multi into the main mixer. Ideal, no, but it worked fine, and back then I couldn't afford DI boxes!

[Tomo]

Unbalanced signals are strange things - sometimes you'll have no problems with very long runs, and sometimes you'll be unable to go a couple of metres before it starts to create huge amounts of hum.

[Bobbsy]

Spot on Tomo. The other thing to add is that the unbalanced connection that worked flawlessly during sound check will invariably fail once the audience is in. I think it's some law of physics or something...maybe the Heisenberg Unbalanced Certainty Theorem.

 

Seriously, problems CAN develop suddenly and unexpectedly: it's rarely worth the risk.

 

Bob

[benatkinson]

Thanks for the response,

 

I sadly dont have enough cash to get some more DI boxes so could somebody give me a straigh answer.

 

Long Phono cable OR Convert to XLR and run to the DI.

 

 

Thanks, Ben

[Bobbsy]

Straight answer: it probably won't make much difference.

 

IF, by phono cable you mean the sort of cheap "bell wire" stuff and IF the XLR cable you use is at least properly screened audio cable, the XLR route might be slightly more resistant to electrical interference. Without a DI box at the source end, it'll still be an unbalanced signal even though you're using XLR connectors. Please note that simply saying "phono" or "XLR" is merely specifying the connectors; it says nothing about the quality of cable used.

 

If it was me I'd probably use the converter and XLR, if only because two 20 metre cables with phono connectors is not usually much use whereas the same lenght of mic cable is always handy. However, without a local DI, in either case you're still feeding an unbalanced signal a heck of a long way so it's going to be at risk of random hums clicks and buzzes.

 

Bob

[Ynot]

Thanks for the response,

I sadly dont have enough cash to get some more DI boxes so could somebody give me a straigh answer.

Hmmm... I thought you'd actually had a couple of straight answers.

And you don't need to BUY the DI's - you should be able to hire a couple of mono's or one stereo for less than a tenner!.