EZB Posted August 27, 2004 Share Posted August 27, 2004 I use a Mackie SRM450 as my amp, which takes an XLR in. Until today, I was using a keyboard mixer with an XLR out to feed it. The mixer just died in a way I won't get into (old Yammie DMP11 I bought in 1988--difficult to repair), and I need to buy a new mixer. I am tempted by some of the little ART personal mixers out there given how easy they would be to pack in a gig bag (I could leave my rack at home as I am not using any other rack gear at the moment) and how cheap they are. (I gig rarely and don't need something fabulous.) The ART's only have a 1/4" unbalanced outs. I have nothing against 1/4", and I don't do long enough cable runs to need low-Z balanced XLR anyway, so I am think I am fine using a simple XLR to 1/4" cable to connect mixer to Mackie. Or am I?? All of the hi-Z/low-Z balanced/unbalanced transformer/DI stuff has always been a bit mystifying to me. Am I going to suffer any major signal degradation and/or volume level mismatches if I run with this configuration. I'd rather not buy a DI, or anything else that adds to the list of things I am likely to lose right before a gig if I can avoid it. Thanks Link to comment Share on other sites More sharing options...
synthetic Posted August 28, 2004 Share Posted August 28, 2004 For a cable run around 12 feet or less I doubt you'll notice a difference. You might need to turn the amp up a bit more, since balanced signals a usually hotter than unbalanced. Or you could move up to something like a Mackie mixer with balanced 1/4" outputs and get a TRS to XLR cable to plus into the amp. Link to comment Share on other sites More sharing options...
Bartolomeo Posted August 28, 2004 Share Posted August 28, 2004 The main advantages of balanced lines have to do with immunity to common-mode noise, ground loops, and RF interference. Therefore, as an abstract engineering matter, you don't need them unless you have long runs, are right next to an AM broadcast transmitter, are in a building with grounding problems, or are uncommonly persnickety about noise. Balanced lines make more of a difference with mic levels than line levels, because the higher levels drown out the noise to a greater degree. Aside from that, you have to watch compatibility. Balanced line levels are nominally +4 dBm into 600 ohms, while unbalanced levels are nominally -10 dBm into (usually) 600 ohms. If you just solder up a cable or use a simple adapter to connect up, the levels will be wrong. Depending on the equipment, that may not matter. You can try soldering up a cable with an XLR on one end and a phone plug on the other. Chances are it will work OK, though you may have to crank up the gain on your amp or elsewhere in the signal path to get full volume. You can try making one up and just plugging in your keyboard without a mixer, to see what it will be like. If that works, go for it. Otherwise, there are reasonably priced mixers out there that have balanced outputs. Bartolomeo Link to comment Share on other sites More sharing options...
EZB Posted August 28, 2004 Author Share Posted August 28, 2004 OK--thanks. So if I use the 1/4" to XLR cable, I may have to increase the gain on either the sending or receiving end as the Mackie is only expecting +4, but is actually getting a stronger -10 signal. True? If so, I can live with that. I sometimes use my Mackie as a monitor, and use the 2nd XLR connector on it (which functions as a thru) to go to the FOH system. If I run with the config above, I guess the signal coming out of the Mackie XLR into the FOH will be roughly +4 as before, so I won't be creating a major headache for an engineer (at last not one that can't be addressed with a trim pot). True? Link to comment Share on other sites More sharing options...
Bartolomeo Posted August 28, 2004 Share Posted August 28, 2004 Originally posted by EZB: OK--thanks. So if I use the 1/4" to XLR cable, I may have to increase the gain on either the sending or receiving end as the Mackie is only expecting +4, but is actually getting a stronger -10 signal. True? If so, I can live with that. The -10 dBm signal is weaker than the +4 signal, so switching to the -10, you will have to turn up the gain. I sometimes use my Mackie as a monitor, and use the 2nd XLR connector on it (which functions as a thru) to go to the FOH system. If I run with the config above, I guess the signal coming out of the Mackie XLR into the FOH will be roughly +4 as before, so I won't be creating a major headache for an engineer (at last not one that can't be addressed with a trim pot). True?It depends. Oftentimes XLR "thru" connections are wired like a Y cord, in which case the FOH will see the lower levels. Also, the signal will be unbalanced. Most often, the FOH engineer will have a direct box to deal with this. The difference in levels can be dealt with by adjusting trim, yes. A few amps have a true balanced XLR out. I believe that the KP-200s does, though I haven't seen a schematic so I don't know for sure. Link to comment Share on other sites More sharing options...
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