'Y' xlr cables?

C

coolsoundman

New member
I don't know if this type of topic belongs here or not, but here goes. I have two firepods which now gives me 16 channels and I have a live mix which is also 16 channels. Sometime in the future I want to do a live recording of a gig using my firepods. i've heard of a splitter snake, but I think they are to expensive for me right now. So, I was thinking and came to the idea of using the 'y' xlr cable. connecting the female end to the main snake and the male end to the mixer and running a 6' cable to my firepods. would this work or would I go ahead and invest into a splitter snake? :o
 
could be very problematic. will it produce signal to both places yes but usable by both probably not on all counts. The reason we use splitters is for both transformer isolation and ground lifts and to maintain correct impedance. If you are using keyboards, direct instruments and things of that nature you will need these treatments. if you could float bout 600, ART has a new single rkmnt 8 chan splitter i think it called the RS8 for 300 you would need two. otherwise both the performance and recordings may be plagued with noise.
 
If you are running the mics into a mixer first, you could always tap the inserts. Just plug a 1/4" cable into the insert until you feel the first click. Plug the other end into the inputs on the Firepod. Of course the mixer would have to have inserts on all the channels. Also if you are patching anything into the inserts you might be screwed.
 
Passive XLR splits will be fine 99.5% of the time, if you have your shit together as far as AC grounding goes.

Splitter snakes are just XLR Y cables in a box, unless they say they have isolated outputs.
 
Aren't there almost always impedance issues with simple Y splitting?

Are Y cables ever really good? I'm not an electronics expert, but when I worked at a radio station years ago, I remember making resistor pads (H-pads) to split signals (or just to match different signals) because of impedance issues. If you have a 600-ohm load feeding two inputs expecting 600 ohms, aren't you delivering only 300 ohms to each? And as a result making a mismatch which will lead to a tonal problem (seems to usually roll off the bottom end).

Or is this negligible in lower impedance situations? I remember making pads more often for unbalanced, higher impedance signals.

However, I'm guessing that by the quantity of posts mentioning splitting audio signals that many people do it, and that most seem to be happy with the results. I've also been wondering if I'm splitting hairs or missing some greater factor by the fact that some mixer manufacturers recommend tapping the inserts to split the signal.
 
The capacitance-related frequency issues for sure are less noticeable at the lower impedances....not even an issue in a single split, if you ask me. And shitty transformers will give you bad results....not worth it unless you have some serious cash to lay out..start at about $65/channel....unless you have some bad bad interference problems....which I'd rather confront with quad cable instead of bad trannies...but if you go that way take the direct side for the recording, and the iso for FOH.
 
The last time I recorded live, I ran my own mics for drums, guitar and bass. The vocals I got by tapping the inserts. I don't think having singers singing into two mics was going to look cool.:D If you are doing both the live sound and the recording this might be a lot of mics.
 
Whale Bone said:
Are Y cables ever really good? I'm not an electronics expert, but when I worked at a radio station years ago, I remember making resistor pads (H-pads) to split signals (or just to match different signals) because of impedance issues. If you have a 600-ohm load feeding two inputs expecting 600 ohms, aren't you delivering only 300 ohms to each? And as a result making a mismatch which will lead to a tonal problem (seems to usually roll off the bottom end).

Or is this negligible in lower impedance situations? I remember making pads more often for unbalanced, higher impedance signals.
Click to expand...

Most mics aren't 600 ohm output, and very very few interfaces/recorders, if any modern ones, are going to be 600 ohm input.

The likely case is a 150 to 250 ohm mic into two 1K ohm inputs. That presents a 500 ohm load to the mic, which is heavy-ish, but most mics won't care. The level will drop a couple of dB. Dynamic mics or transfomer-output condensers will have their tone change a little. A transformer would provide isolation, but loading issues are basically the same, except the transformer can trade away a few more dB of signal to keep the load on the mic lighter. A pad can do the same thing, but less elegantly.

Best solution, assuming you have total control of the live mix and pre-EQ direct outs (or just minimize fussing with EQ and gain trim), is to use direct outs. Also, the Firepod would have to have line-level inputs (if it doesn't, inline pads could fix that problem). Next best if you don't have direct outs is tapping the inserts, unless you really need them for compression. Even then, you could split the inserts . . .

Otherwise, I agree with boingo, just split the mics.
 
It wasn't occurring to me that mic pre inputs are 1K+. Yeah, 1: I guess I am splitting hairs; and 2: I think we might've been matching gear that was going from high to low, or the chief engineer was just splitting hairs...
 
when you paralell the inputs of those boards the mics will need to output more current... and since they aren't good current sources to begin with the voltages will drop... how much is hard to say without knowing somethings about the two boards involved... also you could be seriously screwed if any of the mics are condensers... best to find someway to isolate them...
 
coolsoundman said:
I'm refering to the live mix board. A mackie cfx20. I would like to do a live recording using the mix board and split the signal to the firepods.
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Ok. I used to have a CFX 20. Since there's not individual line outs on there, the best you can do is to send the signal for each track out using the 'insert the cable until you feel it click once' method in each channels insert. So unless you use outboard effects in those inserts, I would suggest you do it that way.

I used that board to record many, many live shows - and I can offer some more specific advice, too: The inserts on my CFX20 were really, and I mean REALLY flakey. I had to be really, really careful when using the inserts to send the signal over to a recording device, or the live channel's signal would cut out....as if I had shoved the cable all the way into the inserts. Also, the signal from the CFX20's send is HOT, and it will clip your Firepods' converters if you aren't paying close attention to your gain settings on the Mackie. It was always a struggle for me when I used that thing to record a live band's show to strike a balance between getting enough gain to have a usable signal for the live mix, while not clipping the converters getting signal from the inserts of each channel...but it is definitely doable, and it works very well when you get it set right, too.

Good luck, and I hope something I typed helps you out!

P.S. @ mshilarious: What happens if you parallel a mic to two preamps like you were talking about and turn phantom power on through one of the pres? Will it fry the other one, or cut the voltage going to the mic in half, or do nothing at all?
 
TyphoidHippo said:
P.S. @ mshilarious: What happens if you parallel a mic to two preamps like you were talking about and turn phantom power on through one of the pres? Will it fry the other one, or cut the voltage going to the mic in half, or do nothing at all?
Click to expand...

dont want to speak for him... but seems to me there's no way to predict this without seeing schemos of the equipment in question...

possible issues because of differing grounds...

possibly the impedence of one is appreciably lower and the phantom from the other is sucked down till burning the build out resistors in the phantom circuit or the phantom could fail entirely...

bottom line dont use Ycords...
 
dementedchord said:
dont want to speak for him... but seems to me there's no way to predict this without seeing schemos of the equipment in question...

possible issues because of differing grounds...

possibly the impedence of one is appreciably lower and the phantom from the other is sucked down till burning the build out resistors in the phantom circuit or the phantom could fail entirely...

bottom line dont use Ycords...
Click to expand...

Yes, it would be somewhat unpredictable. But I think we have to assume, to start with, that gear is not absolute poorly-designed garbage (if it is, why record with it?). For example, 48V/6800 ohms = 7mA * 48V = 0.34W. That's grounding out the phantom supply, worst case scenario. So in theory, a phantom supply resistor should be 1/2W rated. But it probably won't die a horrible death even if it's 1/4W; the phantom standard is supposed to be 10mA per input, which is 5mA per resistor, or 0.24W.

So I don't worry too much about the phantom resistors. Resistors are fairly durable. Opamps often are not. But again, you'd have to presume that the gear was not garbage, so you hope there is some overvoltage protection at the gear's input. Otherwise, the mere act of switching phantom on or hotpatching a cable could destroy the opamp. Some opamps have internal protection, but diodes are very very cheap, so why not use them? And most schemos I've seen do.

Anyway. So put caps in series with the split to the recorder (where phantom is presumably coming from the live board). That may be unnecessary, as that box most probably has its own input caps.

Even without that, you probably don't want to turn on both phantom supplies. Most likely that would just cause a drop in the phantom supply impedance, which for most microphones would not matter at all. But it still seems funny, doesn't it?

If you have a problem with the ground reference between the two bits of gear, that is a potential problem irrespective of phantom power. If you want a Y cable to work, you ought to be sure the bits have a low-impedance connection to a common ground. The phantom voltage reference (pin 1) ought to be chassis ground, although in many boxes that may not be true.

If there is a difference in signal ground, you'll have the same problem with using an unbalanced insert send . . .
 
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