What is true balance?

Aaron323 · 1st January 2006, 06:28 PM

What is true balance output? Mark Levinson says it has true balance design from input to output but how does it convert a RCA input to balance?

What is non-"true balance"?

What are the differences between these two?

If I have an XLR output, how do I know it is true balance?

Too many questions. Thank you.

AndrewT · 2nd January 2006, 07:55 AM

Hi,
it appears that the most important aspect of a balanced output is very accurate balancing of the source impedances.
The voltages seem to be less important due to the next stage being able to amplify the DIFFERENCE between the voltages.

It is the ability of the balanced input amp to work on the voltage difference that allows it to accept RCA unbalanced input with just acceptable performance.

Look up http://www.rane.com/note110.html for some balanced to unbalanced and back interconnects. there is a good section on signal grounding as well.

moamps · 2nd January 2006, 08:48 AM

http://www.dself.dsl.pipex.com/ampin...d/balanced.htm

wuffwaff · 2nd January 2006, 08:51 AM

Hi,

Mark Levinson refers to true balance when they use two amps (one for +IN, one for -IN) and not an inverter stage at the end of a normal gain stage.

You should be able to telll if yours is "true balance" by looking at the schematic or inside the amp.

William

Aaron323 · 2nd January 2006, 03:59 PM

Thank you for the responses but I am not an electronic guru that is why I am having some difficulties to understand the information as stated in the link. Anyhow, appreciate the help but would be grateful if someone can put it in more layman terms.

anatech · 3rd January 2006, 12:53 AM

Hi Aaron,
Don't you love advertising guys? Unless you know electronics and can read the schematic, there is no way to know for sure if something is properly balanced. In studio terms, "balanced" means both phases of the XLR connector are driven exactly equally, 180° out of phase. The 0 Vu level is +4 dBm (ref 600 ohms, 0.775V). That would be a good hint that it is correct. A microphone operates at a much lower level, but is balanced.

To add to the confusion, there are wiring differences between the US standard and Japanese standard. One of the phases and cable shield are swapped. I can't remember off-hand which phase it is.

A sure bet something is wrong is a 1/4" plug labeled both ways. This is almost always a +4dBm /-10dBu type. It's unbalanced as the two phases run at different levels. Avoid unless you plan to run at -10 dBu (around 0.316 V) Your RCA's standard level is also -10dBu.

Have I confused you?

-Chris

Peter Daniel · 3rd January 2006, 01:00 AM

Quote:

Originally posted by Aaron323
Mark Levinson says it has true balance design from input to output but how does it convert a RCA input to balance?

That's how they do it in ML380 preamp:

Aaron323 · 5th January 2006, 07:07 AM

Many thanks for the input.

For the RCA to balance conversion, I can see there is one output from OPA627 to two opamp. How does it divide the +ve and -ve because there is no caps to shift the phrase?

richie00boy · 5th January 2006, 07:38 AM

The top op-amp is non-inverting and the bottom is inverting... simple

1st January 2006, 06:28 PM	#1
Aaron323 diyAudio Member Join Date: Dec 2005 Location: New York	What is true balance? What is true balance output? Mark Levinson says it has true balance design from input to output but how does it convert a RCA input to balance? What is non-"true balance"? What are the differences between these two? If I have an XLR output, how do I know it is true balance? Too many questions. Thank you.

2nd January 2006, 07:55 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, it appears that the most important aspect of a balanced output is very accurate balancing of the source impedances. The voltages seem to be less important due to the next stage being able to amplify the DIFFERENCE between the voltages. It is the ability of the balanced input amp to work on the voltage difference that allows it to accept RCA unbalanced input with just acceptable performance. Look up http://www.rane.com/note110.html for some balanced to unbalanced and back interconnects. there is a good section on signal grounding as well. __________________ regards Andrew T.

2nd January 2006, 08:51 AM	#4
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	Hi, Mark Levinson refers to true balance when they use two amps (one for +IN, one for -IN) and not an inverter stage at the end of a normal gain stage. You should be able to telll if yours is "true balance" by looking at the schematic or inside the amp. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

5th January 2006, 07:38 AM	#9
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	The top op-amp is non-inverting and the bottom is inverting... simple __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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2nd January 2006, 08:48 AM	#3
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	http://www.dself.dsl.pipex.com/ampin...d/balanced.htm

2nd January 2006, 03:59 PM	#5
Aaron323 diyAudio Member Join Date: Dec 2005 Location: New York	Thank you for the responses but I am not an electronic guru that is why I am having some difficulties to understand the information as stated in the link. Anyhow, appreciate the help but would be grateful if someone can put it in more layman terms.

3rd January 2006, 12:53 AM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Aaron, Don't you love advertising guys? Unless you know electronics and can read the schematic, there is no way to know for sure if something is properly balanced. In studio terms, "balanced" means both phases of the XLR connector are driven exactly equally, 180° out of phase. The 0 Vu level is +4 dBm (ref 600 ohms, 0.775V). That would be a good hint that it is correct. A microphone operates at a much lower level, but is balanced. To add to the confusion, there are wiring differences between the US standard and Japanese standard. One of the phases and cable shield are swapped. I can't remember off-hand which phase it is. A sure bet something is wrong is a 1/4" plug labeled both ways. This is almost always a +4dBm /-10dBu type. It's unbalanced as the two phases run at different levels. Avoid unless you plan to run at -10 dBu (around 0.316 V) Your RCA's standard level is also -10dBu. Have I confused you? -Chris

5th January 2006, 07:07 AM	#8
Aaron323 diyAudio Member Join Date: Dec 2005 Location: New York	Many thanks for the input. For the RCA to balance conversion, I can see there is one output from OPA627 to two opamp. How does it divide the +ve and -ve because there is no caps to shift the phrase?

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