ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3 4 ... 7   Go Down

Author Topic: Pseudo balanced outputs?  (Read 27021 times)

Chris Wintz

  • Newbie
  • *
  • Offline Offline
  • Posts: 12
Re: Pseudo balanced outputs?
« Reply #10 on: February 29, 2012, 12:08:46 am »

Yeah I was talking about playback of tracks with HD24 @ stage . Alesis manual has no reference  of what pseudo balanced outputs means. I'll see what they say.

Hey Irving -- How long are you talking??  50'? 75'? 200'?  I wonder if there's a way to put the remote down a snake line instead.  Keeping the HD24 at FOH....

Logged

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 6668
  • Audio Plumber
Re: Pseudo balanced outputs?
« Reply #11 on: February 29, 2012, 12:24:02 am »

Hey Irving -- How long are you talking??  50'? 75'? 200'?  I wonder if there's a way to put the remote down a snake line instead.  Keeping the HD24 at FOH....

As long as the inputs to the console are balanced, and the connections to the HD24's outputs are wired as balanced TRS connections there should be no problem running the signal 1000'. As long as the impedance to ground of the 2 signal wires is the same it is a balanced circuit, and will benefit from the noise canceling behavior of the balanced input it is driving.

A balanced line level circuit is very noise resistant. Treat the output of the HD24 like a balanced circuit and it will behave like a balanced circuit. Starting on page 20 of the manual the output is described as Tip +, Ring -, Sleeve shield.

Mac
Logged

Chris Wintz

  • Newbie
  • *
  • Offline Offline
  • Posts: 12
Re: Pseudo balanced outputs?
« Reply #12 on: February 29, 2012, 12:56:23 am »

As long as the inputs to the console are balanced, and the connections to the HD24's outputs are wired as balanced TRS connections there should be no problem running the signal 1000'. As long as the impedance to ground of the 2 signal wires is the same it is a balanced circuit, and will benefit from the noise canceling behavior of the balanced input it is driving.

A balanced line level circuit is very noise resistant. Treat the output of the HD24 like a balanced circuit and it will behave like a balanced circuit. Starting on page 20 of the manual the output is described as Tip +, Ring -, Sleeve shield.

Mac

Of course - your entire drive signal path is line-level.  I was thinking of an alternative to having dude on stage having to manage the HD24 interface while entertaining.  Keeping the HD24 at FOH keeps a smaller, simpler interface onstage (better looking too) and should anything go wrong, the FOH guy is probably in a better position to troubleshoot on the fly...

I'm just not sure how the LCR works.  I've found most wired-remotes make it pretty far.  I'd be surprised if it worked down 300' of snake, but 50' or 100' might be worth a shot?...
Logged

Brad Weber

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2209
  • Marietta, GA
Re: Pseudo balanced outputs?
« Reply #13 on: February 29, 2012, 07:56:04 am »

Pseudo-Balanced is a Pseudo technical term, i.e. not an actual technical term.
Look toward the end of http://www.rane.com/note110.html and at "pseudo balanced output" in http://www.rane.com/par-p.html, "pseudo-balanced" may be a 'made up' term but it also seems to be an accepted technical term with a generally accepted definition.

I believe I understand Mac's point but I think it may confuse people, see page 22 in http://www.jensentransformers.com/an/generic%20seminar.pdf for some related discussion.
Logged

Philip Roberts

  • Church and H.O.W. Forums
  • Full Member
  • *
  • Offline Offline
  • Posts: 174
  • South West MI
Re: Pseudo balanced outputs?
« Reply #14 on: February 29, 2012, 10:01:59 am »

I'm just not sure how the LCR works.  I've found most wired-remotes make it pretty far.  I'd be surprised if it worked down 300' of snake, but 50' or 100' might be worth a shot?...
The LRC works by bridging various fixed resistance values across the line ranging from 75 ohms to about 1400 ohms.

See: http://ringbreak.dnd.utwente.nl/~mrjb/electro/

My I'd guess you could go through at least 10-20 ohms of cable loop resistance and have it still work. 24 AWG is 25.67 ohms/1000' so (aka 25.67 ohms for a 500' loop) so my guess is that 200' in typical snake cable would work.

Philip
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16449
  • Hickory, Mississippi, USA
    • Resotune
Re: Pseudo balanced outputs?
« Reply #15 on: February 29, 2012, 10:12:45 am »

Look toward the end of http://www.rane.com/note110.html and at "pseudo balanced output" in http://www.rane.com/par-p.html, "pseudo-balanced" may be a 'made up' term but it also seems to be an accepted technical term with a generally accepted definition.

I believe I understand Mac's point but I think it may confuse people, see page 22 in http://www.jensentransformers.com/an/generic%20seminar.pdf for some related discussion.

+1 the jensen note is more thorough and accurate.

The Rane Glossary is a useful Rosetta stone to use, but not an official standard. That said "Impedance balanced", is still my preferred terminology because it is more literally descriptive of what is going on, while not an official standard term either (AFAIK). I find Pseudo balanced vague (i wasn't sure what it meant, even after googling Alesis documents).

While I am not sure who invented the term "impedance balanced",  Mackie popularized it no doubt because it makes a much stronger sounding FAB bullet point in advertising copy than quasi-pseudo-voodoo balanced, and can cost pennies to add to a product. I don't know if there is some NIH dismissal by Rane of terminology embraced by Mackie, a company more known for marketing than engineering excellence (flame jacket on). I find it an interesting omission that Rane does not list my choice "impedance balanced". I'd dismiss impedance balanced too as not being the real deal, but it actually works pretty well. Psuedo- and Quasi- is code for professionals to avoid which may not be the best advice in this case.

Use whatever terminology you prefer, I will soften my criticism as neither term is official AFAIK. Both pseudo- and quasi- balanced seem pretty widely and interchangeably used, so I will only ask that some additional clarification be added in those cases, as there are multiple active output topologies in use with their own quirks regarding wiring and use. 

Note: my copy of IEEE S-100 (with 23k standard terms defined) was new in 1984 so doesn't have pseudo-, quasi-, or impedance balanced listed. The closest to this variant is "balanced termination" which describes the "same resistance to ground condition". The IEEE reference also considers true balanced lines to contain symmetrical signal feeds so it is in conflict with current modern practice and use of terminology. I am not a stickler to the old standard definition and find modern usage OK (it works).

Sorry if this is TMI, I believe in precision in technical language, and when terminology is not precise, add enough extra description, so the customer can always figure out what you are saying.

JR

PS: I do not mean to discredit the Rane resource. They have apparently made an editors choice on this one term, and appear to be in agreement with many more others than myself. They also know the difference between "bus" and "buss" so win my respect overall. 


 
Logged
Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Jay Barracato

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2025
  • Solomons, MD
Re: Pseudo balanced outputs?
« Reply #16 on: February 29, 2012, 10:16:20 am »

+1 the jensen note is more thorough and accurate.

The Rane Glossary is a useful Rosetta stone to use, but not an official standard. That said "Impedance balanced", is still my preferred terminology because it is more literally descriptive of what is going on, while not an official standard term either (AFAIK). I find Pseudo balanced vague (i wasn't sure what it meant, even after googling Alesis documents).

While I am not sure who invented the term "impedance balanced",  Mackie popularized it no doubt because it makes a much stronger sounding FAB bullet point in advertising copy than quasi-pseudo-voodoo balanced, and can cost pennies to add to a product. I don't know if there is some NIH dismissal by Rane of terminology embraced by Mackie, a company more known for marketing than engineering excellence (flame jacket on). I find it an interesting omission that Rane does not list my choice "impedance balanced". I'd dismiss impedance balanced too as not being the real deal, but it actually works pretty well. Psuedo- and Quasi- is code for professionals to avoid which may not be the best advice in this case.

Use whatever terminology you prefer, I will soften my criticism as neither term is official AFAIK. Both pseudo- and quasi- balanced seem pretty widely and interchangeably used, so I will only ask that some additional clarification be added in those cases, as there are multiple active output topologies in use with their own quirks regarding wiring and use. 

Note: my copy of IEEE S-100 (with 23k standard terms defined) was new in 1984 so doesn't have pseudo-, quasi-, or impedance balanced listed. The closest to this variant is "balanced termination" which describes the "same resistance to ground condition". The IEEE reference also considers true balanced lines to contain symmetrical signal feeds so it is in conflict with current modern practice and use of terminology. I am not a stickler to the old standard definition and find modern usage OK (it works).

Sorry if this is TMI, I believe in precision in technical language, and when terminology is not precise, add enough extra description, so the customer can always figure out what you are saying.

JR

PS: I do not mean to discredit the Rane resource. They have apparently made an editors choice on this one term, and appear to be in agreement with many more others than myself. They also know the difference between "bus" and "buss" so win my respect overall.

With most techs I meet I prefer to forego the buss.
Logged
Jay Barracato

Chris Wintz

  • Newbie
  • *
  • Offline Offline
  • Posts: 12
Re: Pseudo balanced outputs?
« Reply #17 on: February 29, 2012, 10:26:37 pm »

The LRC works by bridging various fixed resistance values across the line ranging from 75 ohms to about 1400 ohms.

See: http://ringbreak.dnd.utwente.nl/~mrjb/electro/

My I'd guess you could go through at least 10-20 ohms of cable loop resistance and have it still work. 24 AWG is 25.67 ohms/1000' so (aka 25.67 ohms for a 500' loop) so my guess is that 200' in typical snake cable would work.

Philip

Nice!  You'd have to stay away from the ISO-split though...
Logged

Jordan Wolf

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1363
  • Location: Collingswood, NJ
Re: Pseudo balanced outputs?
« Reply #18 on: February 29, 2012, 10:54:33 pm »

With most techs I meet I prefer to forego the buss.
What about lecterns...er, podiums...or...


 ::)
Logged
Jordan Wolf
<><

"We want our sound to go into the soul of the audience, and see if it can awaken some little thing in their minds... Cause there are so many sleeping people." - Jimi Hendrix

Nick Hickman

  • Classic LAB
  • Newbie
  • *
  • Offline Offline
  • Posts: 29
    • 100dB sound
Re: Pseudo balanced outputs?
« Reply #19 on: March 02, 2012, 07:14:41 am »

Hi Mac,

It may mean that the impedance to ground is the same for both conductors, but only one has signal voltage on it. Of course that would be an actual balanced circuit, so I don't know what "psuedo" means. What prevents noise PU in the circuit is the input being balanced, and the cable being STP.

Balanced audio has equal, but opposite polarity, signals in each of the 2 conductors in the STP. This has the effect of doubling the signal voltage at the input.

Maybe I'm misunderstanding, but your two paragraphs seem to be saying opposite things.  I disagree with your second paragraph: a balanced audio circuit requires that all parts of the circuit (output, cable, and input) have balanced common-mode impedance (as you describe in your first paragraph), but imposes no requirement for voltage symmetry.  Voltage symmetry might help in some cases, but that's a minor subtlety in comparison.

FWIW, I think calling the topology under discussion "pseudo-balanced" is actually selling it short.  It is (or could be) fully balanced, just not symmetrical (which usually doesn't matter).  I understand Neumann and AKG use the topology for the outputs of some of their microphones.  It has the added advantage that it can be unbalanced by either shorting or floating the cold leg at the driver or receiver without detriment and without change in level or headroom.  Arguably, it's a much better scheme than a cross-coupled ("servo") output which might have symmetrical-ish drive but poor impedance balance.

Nick
Logged

ProSoundWeb Community

Re: Pseudo balanced outputs?
« Reply #19 on: March 02, 2012, 07:14:41 am »


Pages: 1 [2] 3 4 ... 7   Go Up
 



Page created in 0.041 seconds with 24 queries.