Simple Stereo Question
Slump
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#1
22nd April 2012
Old 22nd April 2012
  #1
Gear interested
 

Thread Starter
Simple Stereo Question

Hey guys, just built a pretty basic pre-amp for a contact mic that I plan making "modular" with an altoids tin. I want to have jacks for both the input and output of the pre-amp and just solder up a contact mic with a mono plug at the end. So, i'll end up having a mono jack input into the pre-amp, but my question is if I put a stereo plug output for the output of the pre will I run into any problems? I'm not trying to magically make a mono signal from the mic turn into a stereo signal, I just want a stereo output jack on the pre because it will allow me to record into my interface and recorders much easier with their line-in inputs.
#2
22nd April 2012
Old 22nd April 2012
  #2
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LeeYoo's Avatar
 

A TRS jack socket has an extra contact for the RING.
Up to you if you want to use it, float it, or ground it.
If you shove a mono jack in there, it will be grounded anyway.

Maybe wise to use a "switching" input socket.
These sockets keep the input grounded untill you put a jack in there.
Safer with high impedance inputs.
Leo..
#3
22nd April 2012
Old 22nd April 2012
  #3
Lives for gear
 

Be careful though... most laptops are mono. doesn't the ring on a laptop provide power for the mic? That could be a problem if you were to send the + down the tip and ring.


anyway if you always know that you are plugging into a L/R jack, wiring the tip and ring together to feed both sides shouldn't be a problem. And it would be easy to make a jumper that floats the ring for those occasions when you know that you'll be using a mono input, or add a second output jack to your tin that floats the ring.
#4
22nd April 2012
Old 22nd April 2012
  #4
Gear addict
 

Quote:
Originally Posted by Bill@WelcomeHome View Post
Be careful though... most laptops are mono. doesn't the ring on a laptop provide power for the mic? That could be a problem if you were to send the + down the tip and ring.
On most newer laptops the input is combined mike/line, and the mike input is stereo as well. When it's configured as mike input there's power on both tip and ring. Capacitor coupled outputs are necessary in this case.
#5
22nd April 2012
Old 22nd April 2012
  #5
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Quote:
Originally Posted by Th3_uN1Qu3 View Post
On most newer laptops the input is combined mike/line, and the mike input is stereo as well. When it's configured as mike input there's power on both tip and ring. Capacitor coupled outputs are necessary in this case.
I don't know about "most". I just checked two Lenovo laptops we bought within the last few months, a Compaq and a Dell each less than two years old, none offer line inputs. I miss my old, old laptops with stereo line input, just for running SMARRT.
#6
22nd April 2012
Old 22nd April 2012
  #6
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LeeYoo's Avatar
 

Am I missing something?
O.P. did not mention laptop input, but interface line input.

IMHI, if you MAKE a MONO device, you use MONO sockets for IN and OUT, and sort out problems on following devices.
A TRS socket can be made mono just by grounding the ring contact.

I use a modified singstar interface as a simple line-input>USB device.
Works for two (stereo) electret computer mics as is, but I ripped the mic-pre out.
Leo..
Slump
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#7
23rd April 2012
Old 23rd April 2012
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Thread Starter
Quote:
Originally Posted by LeeYoo View Post
IMHI, if you MAKE a MONO device, you use MONO sockets for IN and OUT, and sort out problems on following devices.
A TRS socket can be made mono just by grounding the ring contact.
So if I were to use a stereo jack i'd have to ground it in a way so that it becomes just a mono jack? Makes sense, so I guess if I were to just use a mono jack to begin with would there be any problems if a TRS plug is always used with the jack? I ask because a TS plug works on some stereo jacks and on others it doesn't, but on the stereo jacks that the TS plug doesn't work on if I plug it in halfway it will work.

Like I said, i'm only going to be connecting a TRS plug into this pre-amp output and the pre-amp is only designed to be amplifying the mono signal of the contact mic, so does a mono jack output make the most sense in this scenario?
#8
23rd April 2012
Old 23rd April 2012
  #8
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LeeYoo's Avatar
 

Scenario 1: Line input is ballanced and you are using a TRS lead. > You have to ground the ring contact of you output socket.
Scenario 2: Line input is ballanced and you are using a TS (guitar) lead. > Ring contact makes no difference.
Scenario 3: Line input is unballanced. > You can use a TRS or a TS lead. > Ring contact makes no difference.
So I would ground the ring contact, or use a mono socket.
Leo..
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