Balanced Input Hookup

dsavitsk · 29th July 2007, 07:46 AM

I am working on a balanced preamp based on this schematic

For the input, I picked up a pair of Cinemag CMLI-15/15 transformers. I'd like to accept both single ended and balanced inputs, but this being my first endeavor into balanced circuits I am not sure of how to connect everything up.

Is it reasonable for balanced input to connect the + and - inputs to the two sides of the primary, and for single ended input to connect the input signal to where the balanced + connects and the input ground to where the balanced - connects? This leaves the balanced ground, but I gather this is often ignored anyway.

David Davenport · 29th July 2007, 09:20 PM

I am confused about how your question is formed so I’ll tell you how I do it. Refer to figure 3 on http://www.raleighaudio.com/active_output.htm

It’s incredibly simple: For balanced input, connect the + signal to the + input and – signal to the – input. For single ended input, connect the signal to the + input and ground to the – input. Switch both sides through your source select switch so you switch +/- for balanced input and +/ground for single ended input.

Dave

dsavitsk · 29th July 2007, 10:05 PM

Thanks Dave. That is what I was trying to say in my own convoluted way. It seemed right, but I wanted to be sure I wasn't missing something.

David Davenport · 30th July 2007, 01:45 AM

Okay good, I thought so but I wasn't sure.

One more thing: use the chassis ground for the single ended ground. Don’t use the internal circuit ground.

Dave

fredriksweden · 30th July 2007, 08:42 AM

Hello Mr.
For balanced signal use + (hot), - (cold) and ground.
On a XLR (Cannon) connector Pin 1 is ground, Pin 2 +(hot) and Pin 3 - (cold).
For unbalanced use: (line signal) you have to solder - and ground together otherwise you lose 30 dB of the signal.
So the RCA connector would be: center tap + shield - and ground.
I have the experience the sound isvery dependant on what transformer you use.
In my opinion the best line-trafos ever made was the German Studer (fitted in their two-track reel to reel models), the German Haufe transformers (fitted in Neumann mics etc.), the Swedish Lundahl trafo model SR501 (specially designed for National Swedish Broadcast); and the German Dynacord trafos (fitted in amplifiers like the Eminent and MV-46).
Cheers Fredrik

29th July 2007, 07:46 AM	#1
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	Balanced Input Hookup I am working on a balanced preamp based on this schematic For the input, I picked up a pair of Cinemag CMLI-15/15 transformers. I'd like to accept both single ended and balanced inputs, but this being my first endeavor into balanced circuits I am not sure of how to connect everything up. Is it reasonable for balanced input to connect the + and - inputs to the two sides of the primary, and for single ended input to connect the input signal to where the balanced + connects and the input ground to where the balanced - connects? This leaves the balanced ground, but I gather this is often ignored anyway. __________________ http://www.ecpaudio.com

29th July 2007, 10:05 PM	#3
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	Thanks Dave. That is what I was trying to say in my own convoluted way. It seemed right, but I wanted to be sure I wasn't missing something. __________________ http://www.ecpaudio.com

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29th July 2007, 09:20 PM	#2
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	I am confused about how your question is formed so I’ll tell you how I do it. Refer to figure 3 on http://www.raleighaudio.com/active_output.htm It’s incredibly simple: For balanced input, connect the + signal to the + input and – signal to the – input. For single ended input, connect the signal to the + input and ground to the – input. Switch both sides through your source select switch so you switch +/- for balanced input and +/ground for single ended input. Dave

30th July 2007, 01:45 AM	#4
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	Okay good, I thought so but I wasn't sure. One more thing: use the chassis ground for the single ended ground. Don’t use the internal circuit ground. Dave

30th July 2007, 08:42 AM	#5
fredriksweden diyAudio Member Join Date: Jul 2007	Hello Mr. For balanced signal use + (hot), - (cold) and ground. On a XLR (Cannon) connector Pin 1 is ground, Pin 2 +(hot) and Pin 3 - (cold). For unbalanced use: (line signal) you have to solder - and ground together otherwise you lose 30 dB of the signal. So the RCA connector would be: center tap + shield - and ground. I have the experience the sound isvery dependant on what transformer you use. In my opinion the best line-trafos ever made was the German Studer (fitted in their two-track reel to reel models), the German Haufe transformers (fitted in Neumann mics etc.), the Swedish Lundahl trafo model SR501 (specially designed for National Swedish Broadcast); and the German Dynacord trafos (fitted in amplifiers like the Eminent and MV-46). Cheers Fredrik

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