2 to 1 passive summer

[Coldsnow]

Hi all,  I need to send 2 mic preamps summed then use another as the makeup gain. I know there would be a resister on each plus and negative line coming in and another strapped across the positive to the negative for impedance.  Any idea on values ? 

 

[okgb]

I'd be curious too , I made a " Y " cord with inline resistors [ don't remember the values ]
for summing two gtr lines together - two pres handling either  2 mics , mic direct , two directs,
but I didn't consider the impedance part of it

 

[pucho812]

yes.

what you need to do is read about passive summing. Do a search, plenty of info  on here as well as that new technology, the internet.

 

[Coldsnow]

Yes, I have done this but would like others opinions.  My thought is to use a 10k resister on each input.  The shunt would be a 266 ohm.  This my thought based on ny daves formula for a 150 desired output impedance, 1600 input, and 2 channels. 

 

[okgb]

Somewhat depends on where it's coming from and going to  [ impedance wise ] for gtrs
I didn't worry about it , but now you mention it think the impedance resistor could be worthy

 

[ruffrecords]

Hi all,  I need to send 2 mic preamps summed then use another as the makeup gain. I know there would be a resister on each plus and negative line coming in and another strapped across the positive to the negative for impedance.  Any idea on values ?

Does the one you are feeding them into have a line input? If it does this could simplify thinks and improve noise performance.

Cheers

Ian

 

[Coldsnow]

Yes it does.  Would that mean no shunt resister.  Just 10ks on each input?

 

[RuudNL]

Why first attenuate the line signals to microphone level, and then boost them to line level?  :
(The signal to noise ratio will suffer.)

 

[Speedskater]

The Rane paper on Wye connectors:

RaneNote - Why Not Wye?

http://www.rane.com/note109.html