Balanced vs Unbalanced

amirm

Banned
Apr 2, 2010
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Seattle, WA
Got a request to post videos on the difference between balanced and unbalanced circuits and interconnects. It is slim picking on youtube in this area. The few videos are focused around pro use. But did find this one short video that is to the point. Quality is lousy ironically with distorted sound but you should be able to put up with it and get a basic understanding. Will keep searching for something better and more in-depth:

 

amirm

Banned
Apr 2, 2010
15,813
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Seattle, WA
Different take on the same topic with perhaps a bit more detail and clarity including the cable structure (coax, XLR, etc).


It is HTML 5 and sounds good at 1.5X speed.
 

amirm

Banned
Apr 2, 2010
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Seattle, WA
OK, we are going to now jump multiple levels in complexity and talk about the differential amplifier used in the above videos. I suggest watching the other videos on how transistors and amplifiers work before watching this.


Video is HTML 5 and the guy speaks slow enough that 1.5X speed works well.
 

microstrip

VIP/Donor
May 30, 2010
20,806
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Amir,

We should be aware that these videos focus on the differential aspect of the receiver and omit the main reason we call it balanced audio - because the output and input impedance of both phases of the signal are respectively the same. Otherwise the induced noise would not be the same in both signal wires.

I remember that the Cello Duet amplifier had a 1 Mohm input impedance in the positive phase and 5 kohm in the negative phase - the input should not be called a balanced input.
 

Occam

[Industry Expert]
Dec 15, 2010
117
1
0
NYC
Microstrip,

To expand on your comments, a proper balanced line level output doesn't require a differential signal, simply a balanced impedance output. This allows a relatively simple implementation/modification of taking a single ended output, adding a xlr connector, and (typically) 2 resistors and a capacitor per channel, and availing oneself of the noise rejection benefits of balanced interfacing.
http://www.jensen-transformers.com/an/an003.pdf
Fig 2.4
Adding_Bal_Out.jpg

Amir - Thanks for finding and posting these well thought out videos

-Paul
 

es347

VIP/Donor & WBF Founding Member
Apr 20, 2010
1,577
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Midwest fly over state..
It's been about 43 years since spending any time with transistor circuits but this brought back a flood of memories. Very enjoyable...thanks for posting Amir.
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
Thanks for additional comments and compliments guys :). I must say, I am surprised myself by the quality of teaching in some of these videos. We will have a much more educated workforce if people augment their formal teaching at school with these kinds of videos.
 

c1ferrari

Member Sponsor & WBF Founding Member
May 15, 2010
2,162
51
1,770
Excellent series, Amir :cool:
Stimulating :p
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
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1,670
Monument, CO
Nice flood of vids, Amir!

I am so used to differential designs that I always have to stop and think how audio distiniguishes "differential" and "balanced" circuits.

BTW, I have not watched the differential circuit video yet, but the schematic shown is actually a quasi-differential circuit to me rather than a fully-differential design because it is two single-ended amplifiers instead of a differential amp.
 

c1ferrari

Member Sponsor & WBF Founding Member
May 15, 2010
2,162
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Don,

Great to see you, here.
Looking forward to further contributions from you :)
 

c1ferrari

Member Sponsor & WBF Founding Member
May 15, 2010
2,162
51
1,770
Thanks, but Amir's doing a great job! The overall flavor of WBF has drifted away from techie stuff, nice to see Amir revitalizing it.

Effusively agree, Don :D
 

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