Mackie DFX6 Phantom Power Problem

[tb1979]

Please excuse another new thread from such a new member - I'm not generally the sort for joining a discussion forum and starting two new threads almost immediately!

 

I've had a Mackie DFX6 mixer for about 3 weeks, which I use mainly for recording podcast-style downloadable audio 'lessons' for my students, but also bought with a view to using as a submixer for orchestra pits in live sound, and smaller sound reinforcement needs at school. Seems like a very useful little mixer for small jobs, and I used a Mackie when I used to do live concert recording at uni so it has nostalgia value :)

 

It's taken me this long to find the problem (should have thoroughly tested earlier!), but mic sockets 3 and 4 are not providing phantom power. Well, they are, but at extremely low voltage (2.7V and 0.7V respectively). I can only assume this has always been the case, as the mixer has had very light treatment so far - in fact, it's hardly left the house.

 

I've got in touch with the supplier who amazed me with an email response within 5 minutes - on a Bank Holiday Sunday! Hopefully this bodes very well for getting the mixer repaired or replaced quickly. Just wondered, though, whether anyone else had come across a similar problem, and whether it is something that could be easily resolved without the need for mixers going around the countryside in courier vans. Obviously at 3 weeks old, I'm not overly interested in voiding my warranty by opening the mixer up, but if someone says "there is a known Mackie DFX-series issue that is resolved by soldering the wire you will find floating around inside to...." or whatever, I'd probably give it a try! :)

[northernaudioman]

Hi,

 

Mic inputs 3 & 4 do not have phantom power, if you check the schematic on the mackie web site:

 

http://www.mackie.com/pdf/dfx_om.pdf

 

it shows no phantom.

 

We have 4 of these and this has caught us out on a couple of occasions!

 

Regards

 

Oliver.

[tb1979]

OK, I am officially a complete idiot.

 

Not only will I get me coat, but also me scarf, wellies, umbrella, gloves, and various other items of clothing.

 

:) ;) :) :)

 

Thank you! Now to grovel profusely to my supplier...

[northernaudioman]

It's an odd decision on Mackie's side, and not clearly explained in their pre-sales info!

 

Maybe a phantom PSU on the front end would help resolve the problem ( AKG / EMO / MTR?? )

 

Super little utility desks though!

 

Regards

 

Oliver.

[tb1979]

Phantom PSU just ordered this minute :P

 

And yes, lovely little desk - so convenient and versatile!

[Beaky]

Thats a bizarre thing to do? I wonder what reasoning came to that conclusion? if the phantom is already there why wouldnt you carry it over all mic inputs with the obvious exception of the stereo ones and even then they could have put 2 XLRs on instead of one? I cant think of any rational reason for doing so? Im not familiar with this mixer but dont most of these small mixers generally have global phantom power (which I really hate) anyway? I just looked at the pdf file and clicked the phantom power on the side menu and it says phantom power is supplied to all mic inputs????? so if your right about the schematic there own text contradicts this?

[MarkPAman]

No, it says "except the stereo channels", so that's all but 1 & 2 on the 6 channel version.

[tb1979]

It is really bizarre (though I'm still feeling silly for not noticing ) - I can only assume there's some way that they can't put +48V on the XLRs without it coming out somewhere they don't want it on the various jack plugs... otherwise, what's to stop someone with more ability than me going in there and adding the 48V by hand? :P

[J Pearce]

Nothing, you could use some capacitors to block the DC from getting to the jack sockets. The preamp should be fine as the mic input is balanced and the common mode rejection of the op-amp will block the DC.