mic splitter

dastrick

huh???
How hard would it be to make a mic splitter? Has anyone had experience doing this? I basically want an 8 in/16 out. Any info would be appreciated.

Thanks.
 
The hardest part is drilling holes in the box . . .

There are a few approaches to a splitter snake. You can just send the mic to two preamps. That could load down the mics a bit much though. If you are running phantom power, then you'd need to designate one of the outputs as the phantom supply. I would add blocking caps to the other side, although that might not be necessary as the other preamp probably has them. If you know it does, you could skip the caps. Some people use transformers on the non-phantom side instead. These can be matching or step-down; step-down will lighten the load on the mics quite a bit, but of course you'll lose some signal level. 8 transformers will be expensive though.
 
Let me tell you what I'll be using the splitter for and you might could tell me what I need.

This will be for a live recording rig. I will want to take the mic signal from the stage and split it. One split will go to the FOH and the other split will go to my firepods.

I've never made anything like this before, but would love to give it a try. If the cost would be comparable to buying a mic splitter, then I'll just buy one. A new ART S8 runs about $240 new.
 
The cost would depend on how much you are willing to spend on transformers, if you decide to go with transformers. A transformerless box could be done for about $60 in parts.

Then the question is the quality of the transformers. The ART specs don't seem horrible, but you can see the low-frequency distortion at 0.3%. That's not terrible; to improve upon it you could easily spend $240 just on the transformers. ART has the advantage of economies of scale, so they can stuff 8 transformers that would probably cost you $10 each into that box and still make a profit.

But transformers with 0.03% distortion are gonna be over $30 each. For mic-level signals distortion will be lower, so I'd be tempted to buy that ART box myself, or just go transformerless and DIY.

The only thing that concerns me about the ART is they mention a couple of times that you must use low-impedance mics, which they say is 150 ohms. That, plus the 2dB insertion loss they spec, make me think their transformers aren't step-down, or at least much. I would go with a 2:1 turns ratio transformer myself; that's a 6dB loss, which is no big deal. Plus a lot of mics aren't 150 ohm (the SM57 is more like 260), and condenser mic distortion can increase at high SPLs as the load on the mic increases. So I would be trying to keep the mics as unloaded as possible . . .
 
What's the advantage/disadvantage of transformer vs. transformerless?

and, thanks for your help

I dont suppose you could run the mics to your firepod and just give foh the line outs? Or get the direct outs from foh's board? I think it'd be better to split at line level, doesn't splitting an already weak mic signal just make it even weaker? Plus with phantom power that's tricky.

If I'm the sound guy, and you were on my house PA, I'd say no way. I'd find another way for you to get a signal, AFTER I've set the gains and have my signal, at a point where you can't mess with the signal going to my mics, pre's, rack, and PA. Especially if I thought your device was home made, I don't know if your device is electrically sound.. Maybe it'll send my mics 96v now, maybe it'll fry my board or pres, who knows.. You could stop a show or damage equipment I'M responsible for! There's easy ways to tap a signal securely, if all the busses and direct outs are used up, a simple patch bay can split the signal anywhere after the pre.
 
I dont suppose you could run the mics to your firepod and just give foh the line outs? Or get the direct outs from foh's board? I think it'd be better to split at line level, doesn't splitting an already weak mic signal just make it even weaker? Plus with phantom power that's tricky.

If I'm the sound guy, and you were on my house PA, I'd say no way. I'd find another way for you to get a signal, AFTER I've set the gains and have my signal, at a point where you can't mess with the signal going to my mics, pre's, rack, and PA. Especially if I thought your device was home made, I don't know if your device is electrically sound.. Maybe it'll send my mics 96v now, maybe it'll fry my board or pres, who knows.. You could stop a show or damage equipment I'M responsible for! There's easy ways to tap a signal securely, if all the busses and direct outs are used up, a simple patch bay can split the signal anywhere after the pre.

Well, it's not quite that bad. Usually the house board would be the main board that supplies phantom and thus gets the direct out. On the other hand, few soundguys would take having the recorder's gear driving the phantom. Especially something hooked to a computer; they would fear the computer would crash, and the phantom would go down with it. For that reason, they wouldn't want to take a line output from the firepod either. Never mind that the firepod doesn't have as many channels are they are probably using.

The benefits of the transformer in this case are limited. Transformers are great when you need to isolate the ground on an unbalanced signal into a bit of balanced kit on another wall circuit. That's the classic case of ground loop. In this case, they provide "isolation", but isolation from what? You can decouple pin 1 on the recorder output anyway (and you would probably want to, since the transformer doesn't address pin 1 at all). The mic signal is balanced and does not need to be referenced to ground, transformer or not. Well, technically it will be ground-referenced by the recorder's input impedance, but that's still common mode.

The transformer gives you DC isolation between the outputs, but a capacitor will do that too.

So the main benefit to me is using a step-down transformer to give the mic a load it is happy with. But you can even do that with a pad; not quite as elegant, but it works . . .
 
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