ext_frequency
Thread Starter
#1
22nd July 2007
Old 22nd July 2007
  #1
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Thread Starter
Question DIY Splitter

After a while of reading up on all the posts, I finally decided to take the plunge and register and make my own thread. Granted this is my first post, hey everyone!!!

Heres the thing, I'm trying to build a splitter system (yes I know one more of us). At the moment I have no transformers as my budget is kind of small right now. After reading around the forum, the most inexpensive way to do such a thing is parellel splitting the inputs, or pretty much a y cable in a box. I understand what needs to be done on paper (schematic-wise) but how would you go about doing this physically? I have xlr inputs going out to 2 multipins, do I

a) solder 2 cables merged together at the xlr solder cup,
b) cut the cable in the middle and attach the second cable,
c) solder 2 cables at one of the outputs
d) something I haven't thought of yet

The whole thing is that I want to make the unit look as clean as possible inside, inspired by the whirlwind splitters, which way is best or is there another way to do such a thing. In this pdf this scehmatic would be figure 1 http://www.audiosystemsgroup.com/Mic_Splitters.pdf

One more thing, where can I find switches for ground lifts, and which type would you recommend? toggle vs paddle etc, and which ones

If anyone can provide either a breakdown, or maybe pictures I would really appreciate it!! Also if I wanted to do sub inputs, using either dt12 or w1's, can I just parrallel wire them with the xlr inputs? And again, how would this look physically? Just happen to have a hard time visulizing everything.
#2
22nd July 2007
Old 22nd July 2007
  #2
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Remoteness's Avatar
Welcome to the forum.

Here’s the thing, don’t try to build a splitter system, build a splitter system.
You’ll be much better off doing it than trying to do it.
Plenty of research and planning is the way to go.
You seem to be doing that and that’s a very good thing.

Even though your budget doesn’t call for transformers, plan for them in the future.
Design your splitter so you can drop them into the box at some future date.
Find a transformer you can afford; size it up and design the box around them.
Add extra length to your cable wiring so you can add them in without having to redo much of the wiring.

It’s the easy way to do it especially if you’re not consider adding XFMRs in the future is to solder the two multipin cables together at the XLR solder cup.
It’s a very simple task.

Another way is to double up the wiring on one of the multipins.
This method should be used when you know (for sure) you’ll never add XFMRs to the box.

Small barrier strips (where the XFMRs will go in the future) is a good way to deal with this.
Then all you’ll have to do is remove the strips and add the XFMRs.
The cable layout and wiring is already done.

I’ve purchase many of my switches from Switches Unlimited in LIC, NY.
I also get them from Whirlwind when applicable.

I would avoid long toggle or paddle switches unless they’re protected with an outer shield.
A low profile rocker switch just like you'd see on a Whirlwind box is your best best

Sub snake inputs along with XLRs are a common thing.
The DT12, etc. are parallel wired to the XLR inputs.
We have parallel wired input and output multipins to XLRs when necessary.
ext_frequency
Thread Starter
#3
22nd July 2007
Old 22nd July 2007
  #3
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Thread Starter
hey thanks for that very detailed post. I think I got it now, just one question, I was checking out the schematics that jensen give out, they mention using resistors and capacitors in the circuit, that would call for using a pcb, would using a splitter built on a pcb, be rugged enough to support life on the road?
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LX3
#4
24th July 2007
Old 24th July 2007
  #4
LX3
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Quote:
Originally Posted by ext_frequency View Post
hey thanks for that very detailed post. I think I got it now, just one question, I was checking out the schematics that jensen give out, they mention using resistors and capacitors in the circuit, that would call for using a pcb, would using a splitter built on a pcb, be rugged enough to support life on the road?
I based my design on some of those Jensen schematics too. Mine has never failed me, and it's all built around PCB modules for each channel. Can't say any of the rented splitters I've run into at gigs have shown the same reliability.

Whether you're using PCBs or hard-wiring, you need to think carefully about where the points of failure might be, and take steps to ensure that they don't fail.

If you're just mounting resistors and caps on a PCB, there should be no problem. A PCB-mounting transformer changes things a little, since it's a fairly hefty lump of iron, so you need to think what the effects of vibration might be - potential for cracking PCB tracks perhaps.

Also, I should say that my splitter ended up costing more in raw parts than buying a commercial transformer splitter from the likes of whirlwind. Not to mention the two years of design and construction that went into it. But the end result is that I have exactly the splitter I want. Apart from the fact I need a couple more now!

Paul
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#5
16th August 2007
Old 16th August 2007
  #5
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didn't want to start a whole new thread...

so i'm gonna hijack.

simple question: from memory a passive, transformer isolated mic-split uses a 1-1 600 ohm transformer, is this correct?
LX3
#6
17th August 2007
Old 17th August 2007
  #6
LX3
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Hi there

Apologies for my unintentionally facetious answer, but use transformers which are specifically made for splitting mic signals. Yes, I assume they have a 1:1 turns ratio (so in theory, V-in will equal V-out) - check the specs, it's not a parameter that I've paid much attention to, but certainly my Lundahls iso outputs throw out the same level as they see at the input (near as damnit).

You also need to decide if you want transformers with just a single secondary, or two. Two is generally more versatile.

The system impedance (i.e. that seen by the mic) depends on the load impedance(s) connected to the outputs, because as I understand it, the transformer reflects the load impedance back onto the primary. How the actual impedance of the transformer itself relates to that I don't know, I wouldn't panic about it.

Shielding is also important IMO. These are really low level signals, so even though they're balanced, they're potentially susceptible to interference.

The other issue with splitter transformers is how much level they'll cope with before they start to distort (I think due to magnetic saturation in the core... wow, I haven't thought about this stuff for a very long time!). The best ones handle tons of signal, more than you're ever likely to get out of a microphone... although they're not so happy working at line level... I use pads on the occasions I need to split line level signals and that seems to work fine. But lots of headroom is always good. Peaks from high-output capacitor mics can end up almost line-level!

If you choose a dedicated mic splitter transformer from Lundahl or Jensen, you won't go wrong, and although it's quite an investment, it's one you'll never regret. Building a splitter box with cheaper transformers will doubtless work, and you can always upgrade them if you design the unit in a way that makes this feasible... but frankly, who wants to build something like this twice? As Steve said, plan carefully and try to get it right first time, because it's no fun taking it all apart and starting over.

Jensen and Lundahl both provide very thorough specifications for their transformers on their websites. Worth pouring over for a few hours!

(Which other transformer manufacturers make good splitter transformers out of interest? Sowter? Cinemag? Others?)

That's my humble opinion anyhow. You're all very welcome to correct any inaccuracies - I'm working from memory here.

Paul

And yay, just realised that was my 100th post! Hope it was a useful one.
#7
10th May 2010
Old 10th May 2010
  #7
Gear interested
resistor splitter help

What about resistor mic splitters?

I found this drawing in a book on location recording, and since it is so cheap to build I'm gonna give it a try.

Can anybody help a great electronics ignorant complete info on the various parts, like voltage or wattage of the various resistors and the capacitor in the RFI filter.
About the RFI filter the author doesn't specify if the resistor is of the metal type, and what type is the capacitor.

can anybody help?

all the best
Attached Thumbnails
DIY Splitter-resistorsplitter.jpg  
#8
10th May 2010
Old 10th May 2010
  #8
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Quote:
Originally Posted by andrplx View Post
Can anybody help a great electronics ignorant complete info on the various parts, like voltage or wattage of the various resistors and the capacitor in the RFI filter.
About the RFI filter the author doesn't specify if the resistor is of the metal type, and what type is the capacitor.

can anybody help?

all the best
Use all metal film 1% tolerance resistors. 1/4W should do you more than fine.

As for the cap, you can use a polyester film. Yellow axial type should be more than ideal. Or WMA type. Not so critical. It won't be passing audio signal anyway. So you don't need to buy the most expensive one. Most manufacturers sometimes even use the cheapest of the cheap ceramic "lentil" capacitors in there so there you go.

B.
#9
10th May 2010
Old 10th May 2010
  #9
Lives for gear
 

Quote:
Originally Posted by andrplx View Post
What about resistor mic splitters?

I found this drawing in a book on location recording, and since it is so cheap to build I'm gonna give it a try.

Can anybody help a great electronics ignorant complete info on the various parts, like voltage or wattage of the various resistors and the capacitor in the RFI filter.
About the RFI filter the author doesn't specify if the resistor is of the metal type, and what type is the capacitor.

can anybody help?

all the best
My advise is don't do it. The resistors must be exactly the same resistance (and stay the same over time) or you'll have issues. It really doesn't provide isolation anyway. Those setups are often used for unbalanced summing but I wouldn't do it for a balanced application.
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