Parallel outputs (split outputs)

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JAY X

Well-known member
Joined
Jan 9, 2009
Messages
683
Hi Friends!

I'm building a summing mixer that has two opamps and two transformers at the output stage that balances the signals.

As there are only one stereo pair, many people suggest to use an external patchbay to split the output for monitoring.

the question is if i can do the signal split inside. ¿ where? ¿how?

I even thought about to put replacement cards of a patchbay.... ???

Thank you for your help!

JAY X
 
Audio is not wood.

You do NOT need a Big Hammer to "split" audio.

You have just one water-pipe from street, for kitchen and bathroom and maybe upstairs bathroom. How do you "split" water? You just use Y or T connectors, and connect all the faucets in parallel.

It is even easier in audio. Just install a second jack(s) and wire them to the first jack(s).
 
Thanks PRR!

I did not figure it would be so simple. because i read that splitting the audio path causes -6db reduction in output .

I forgot to mention that i used  two 1:1 sowter transformers.

Thanks again

JAY X



 
passively splitting outputs is a common practice and for good reason... it works!  ;)

it is true that you will loose some gain when you passively split, but it is completely dependent on the impz of the output of your source (and drive capability) and the input impz of your gear that your splitting too. you may loose a few dB, but you can split line level signal all day long and not worry about it

now if you were splitting mic level signal... this would be a different discussion entirely!


 
there are applications where an active transformer coupled splitting is the best to do.
(lets say distributing an "on air" signal to different places ...)
 
> i read that splitting the audio path causes -6db reduction in output.

That can be true in specific cases. Or you can have a 3dB increase in total output. Like two speakers on one modern amplifier will usually reach almost double total power.

Go back to the water-pipe analogy. Say you have a fire-hose designed to flow a LOT of water through one nozzle onto a fire. Now add a Y-connector to feed two nozzles. Each nozzle will flow less than the one nozzle. The sum of the two nozzles may be same, more, or less, than the one nozzle, depending on relative sizes.

Now take that fire-hose and Y-adapt it to a drinking fountain. Obviously the drinking nozzle will be much smaller than the fire nozzle. The flow from the fire nozzle is hardly affected when the drinking nozzle is added. You could add several drinking nozzles without much change in the flow. Or you can remove the fire nozzle, Y-connect dozens of drinking fountains, and the flow to each one changes very-little when other fountains are turned on or off.

Most modern audio outputs are 600 ohms or less. Most modern audio inputs are 10K or more. A high impedance is like a small nozzle. So the output is like a 4mm pipe. Each input is like a 1mm pipe. It would take 16 inputs to fully-load the 4mm output. So 1 or 2 or 3 inputs on one output all work fine, just like you can use 1, 2, 3 or more drinking fountains in an office or school with good size main water pipe. When Ivy takes a drink, her water stream does not drop much when Jay and Kay start drinking.

True, if Lee May Nan Opie Pam Quincy and Rodney ALL use a fountain at the same time, Ivy's stream may drop a bit.

> distributing an "on air" signal to different places ...

Yes, in Critical situations, you take more care.

A shorted wire is like a big hole in the pipe. If Ivy MUST have a consistent water flow, and if Jay might "accidentally" open a 4mm hole in the 4mm main pipe, you have a problem. There are ways to handle this gracefully. Give Jay only a small pipe to mess with. Give Ivy her own booster-pump. But in the simple case of Recorder and Monitor, accidents are unlikely and any short is liable to require fixing before the work can go on.
 
Sarcastic Sound said:
passively splitting outputs is a common practice and for good reason... it works!  ;)

it is true that you will loose some gain when you passively split, but it is completely dependent on the impz of the output of your source (and drive capability) and the input impz of your gear that your splitting too. you may loose a few dB, but you can split line level signal all day long and not worry about it

In a modern bridging connection, you'll lose (not loose) a fraction of a dB. Consider: output Z around 50 ohms, input Z over 10 k ohms. Do the math. Not at all significant.

now if you were splitting mic level signal... this would be a different discussion entirely!

Same thing applies, and us live sound guys use passive hardwired splits all the time with very few issues. While the output Z of the SM58 is 150 ohms, most mic preamps are on the order of 2k input Z, so splitting into two inputs (for, say, FOH console and monitor desk) still isn't really an issue. And you can compensate for that fraction-of-a-dB loss by turning the input trim up a skosh.

-a



[/quote]
 
I suck at grammer  ::)

but not impz! (or math!)  ;D

I suppose I've got too many "worst case scenarios" under my belt to make open ended statements without explanations. I'll try to be more careful about that before I have EVERYONE telling me things I already know.  ;)





 

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