is this splitter reducing quality

Posted: Sat Apr 28, 2007 1:29 am

I made my 1st y splitter. my design is a bit different than others I've seen so I want to make sure there is no obvious quality problem with my design before I wire all my mic pre outs this way. I'm trying to incorperate a very poor quality 8 channel xlr to xlr snake to send for headphone monitoring to save money.
here's my 1st design: 1 trs( 8") to 1 xlrF (15 feet to xlrM end of snake) and 1 trs (8"). Both trs cables are twisted with the xlrF end of the snake and all 3 leads are tinned together and soldered to the cheap xlrF contacts. the single trs is connected to preamp out, the trs on the dual side is connected to a/d converter and the 15 feet of xlr is connected to mic inputs of mixer for headphones. I would have the snake going to the line in of the 1604 as it is a line level signal but my snake is xlr to xlr.
question 1
Will the use of the 15 feet of very poor quality snake cable to headphones mixer result in noticable amont of degredation to the a/d converter? If so will this be improved by soldering the 3 cables to swthcraft xlr rather than cheap snake xlr? or does all the cable need to be high quality?
2. Will sending the headphones half into mic input of 1604 mixer affect the signal going to a/d converter differntly than if it was going to line in of 1604? Do i need to solder trs on the xlrM end of snake?
I've done many tests with square waves, acoustic guitar and voice on the single channel splitter I made but can't get as conclusive results as I would like and this is one of those things that has to be done right.
I know I need some basic electonics understanding but until then (and then as well) all help is greatly apreciated

Posted: Sat Apr 28, 2007 4:30 am

Probably will affect it some. To what degree? I dunno. You have to do some research on your equipment, and a bit of simple math to see what kind of effect it will have even given a high-quality build.

There is no real info for calculating in poor quality components and/or build. You may be able to get away with splitting a line signal a few times, but a lower-level mic signal will probably suffer degradation more quickly.

A lot of stuff has to be factored in. Your output device has an output impedence, and it should be low. All input devices have input impedences, and they should be relatively high.

If your input impedences for each device are different, it will change the overall impedence the one output sees, but one device may be getting a slightly better signal lessening the signal of the other. When you parallel input impedence, it divides to lower the overall impedence. 10K input and 10K input = 5K overall. (The math gets a touch trickier for unequal impedences, but isn't hard).

And the quality and length of the cables have to be considered. There's also capacitive reactance, and better cables will probably be better.

Having said all that, kluging together two cables is usually not the best way to do that. It would probably be better to buy a good, sturdy metal box and good connectors and build one...or buy one already built. I don't know how you wired the two cables to one plug at the split end, or how you got the connector jackets to fit over two cables. Unless you found some type of specialty connector, I can imagine that you either thinned out the wires to get them both to fit, or you cut through the shielding to bare some wires away from the connectors to "tap into" the cable. If the connector doesn't have the jacket, and it's only got some tape or something around it....not good. Of course, I could be misinterpreting your post about how it's built. If you're actually doing this INSIDE of a metal snake box....? Would be interesting to see a picture.

The following link has some basic explanantions, and some handy formulas. See if it sheds some light:

http://www.whirlwindusa.com/tech03.html

Kapt.Krunch

Posted: Mon Apr 30, 2007 7:43 pm

I just wanted to add something that you might want to consider. You definitely want to make sure everything is shielded, otherwise the signal would be susceptible to RF interference. If the snake is not going to be used for anything else, you could take the male xlr connectors off and replace with male trs connectors. On the other end you could eliminate the box completely and replace with female trs connectors. Then you could go where every other do-it-yourself type has gone, Radio Shack, and get trs Y cord adapters to plug into the female connectors. This would be inexpensive, and at least, it would be shielded along the whole path. But as Kapt. K said, impedence and the length of the cable could cause some degredation. A break out box with separate opamp circuits between the snake and Y cord adapters would probably be a better solution to provide both isolation and some gain to the signal that is being sent to the headphone amps. But, this involves more cost and is more complex as far as building the circuits.

Posted: Tue May 01, 2007 1:31 am

If your spliting a balanced signal you should add a cuple of hundred ohms in serial to the signal and about 2500 in parallell.
This is just aprox. values. you can read more about it trough google.
Damping. loadbalancing. i guess in english.

Posted: Tue May 01, 2007 5:08 pm

thanks for all the info. After doing the math I figured there's no loading problems for my preamps.
The splitter I am hoping to make will have sheilding on all cables. All solders are going to be incased in an xlr. The 15' headphone send cable is small enough that all 3 cables fit in no problem.
here is a high resolution picture
trs---------F xlr
solder here ^. --------trs
\
\
\
\
\
m xlr

All 3 cables are soldered to the contact side of the fxlr. There is nothing connected to the other side of the fxlr. This is eleminating multiple xlr to xlr connections that would exist in a splitter box. This design is the same path that would occur with splitter only minus 2 xlr to xlr connections per signal. I know that the quality of soldering work makes all the difference. I know it might be hard to believe I have good solder skills with my lack of knowage in electronics but i do. probebly 500 hours practice ($2500 canaree and mogami)

I guess it's more opinions I'm looking for in regards to using poor xlr cable to send to the headphone mixer. are any of you using cheaper cable for 1 output of a split (parelelled) pre out?
thanks again for all the help[/url]

Posted: Tue May 01, 2007 5:56 pm

the last picture didn't work out so well. here's a better one

trs-----------F xlr------------trs
oooooooooooo ---------------------------------------------xlr m headphone

---------= cable oooo= nothing

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