DI/Line out question

[Paul_C]

At a recent gig I had all sorts of fun getting set up with the sound guy and I'm trying to establish the best solution once and for all, or at least have a couple of workable options to make setting up quick and simple.

I prefer to be in a position to deal with any problems myself rather than rely on what a sound guy might or might not know

My big fear is that plugging an XLR cable into either my ART TubePac preamp or Little Mark II might cause damage to either unit if the cable has phantom power running through it. (I've enquired on both company's sites for their opinions)

If there's no risk then obviously I have nothing to worry about, but if it's something to be avoided than I need a solution, either a DI box that can offer protection or a cable that I can use that won't allow phantom power through.

Any knowledge/suggestions ?

[BassBod]

I have the same issue with my SWR220 - depending on the age, apparantly these can be fried by phantom power, (although the fix is simply a pair of diodes?) I wouldn't expect Markbass gear to be vulnerable to this, as its all pretty recent designs?

Any passive DI box will protect - I run a jack from a preamp send (or effects send) to a Radial ProI. The other benefit is that you know a passive box will not cause any added hiss and won't run out of headroom (or at least do it with better grace..)

BB

Edited June 23, 2008 by BassBod

[Paul_C]

[quote name='BassBod' post='224866' date='Jun 23 2008, 11:35 AM']I have the same issue with my SWR220 - depending on the age, apparantly these can be fried by phantom power, (although the fix is simply a pair of diodes?) I wouldn't expect Markbass gear to be vulnerable to this, as its all pretty recent designs?

Any passive DI box will protect - I run a jack from a preamp send (or effects send) to a Radial ProI. The other benefit is that you know a passive box will not cause any added hiss and won't run out of headroom (or at least do it with better grace..)

BB[/quote]

I have two solutions so far.

Firstly, a nice man from Markbass emailed to say that the line out will cope with an unexpected dose of phantom power.

Secondly, I have ordered an ART X Direct DI box which I can use if there are issues with the line out (it does suffer from sending quite a hot signal to the desk) and which is battery powered unless it encounters phantom power, whereupon it switches automatically to using that supply. I'll try it both between bass and preamp and between preamp and amp (the second means that I'd send a compressed signal to the desk, which may or may not be advantageous).

No reply from ART regarding phantom power as yet, but it's really not that important now.

[BigRedX]

AFAIK you can make up a XLR male to female lead that will block any phantom power. I had a quick look on the web and couldn't find any details, but I suspect that either one of the electronics experts here or someone on the [url="http://www.soundonsound.com/"]Sound On Sound[/url] forums will know. That way you can leave the lead plugged into your DI and simply connect it to the PA's XLR lead.

[Paul_C]

I've checked the X Direct out this morning and it works perfectly - I've chopped down a mic lead to make an XLR patch lead which can plug into either the line out of the amp or the XLR out of the TubePac preamp (which would cut down the excess of EQs ). I've added some velcro to the outside so I can hook it onto the side of the rack box out of the way, though I might look at ways of velcroing it inside.

I'll plug into the PA at the next rehearsal to make sure it's going to do the job, but it looks like it'll be fine - I do like to arrive at gigs certain of my gear if nothing else.

[BOD2]

For future reference, another option is an [url="http://www.bonnersmusic.co.uk/buy/Art/DTI_Dual_Transformer_Isolator"]Isolating Transformer[/url].

This breaks the physical connection between the phantom powered mixer and the DI device, therefore stoppong phantom power from reaching the device.

It also can be used to eliminate ground loops. It's not particularly cheap but it's one of those "problem solving" devices that a good sound engineer should have handy.

[BigRedX]

I have to say that unless your DI box is used to add something to the sound, you can't beat a good passive transformer-based design.