just realized all my inserts are unbal and all my gear is bal

my mixer has 16 ch of unbal inserts that i use all the time to patch in my yummy diy gear.  problem is all of my gear is balanced so effectively im shorting cold to ground.  is this a problem?  it soulds ok but ive read posts that say noise can be induced?

if you hear no problem, there is no problem.  It's really that easy. 

Hi
I'm faced with that problem too. In my mind I dislike the idea of haveing unbalanced sends and returns but you could add a chip like the DRV134 to balance them on the output and a INA134 to debalance them on the input...but if you don't hear any noise issues then why do it?

yeah thats what i thought.  thanks for the suggestion though. 

Transformer balanced outputs shouldn't have any problems. I have come across a situation with some electronically balanced outputs where shorting the cold output to ground effectively drives one half of a dual opamp into a low-z load (something like 100Ω). In one particular case I ran some kit like this at full output level with XLR pin-3 (cold output) shorted to ground and found the opamp in question was getting pretty darn warm. The other half of said opamp was driving pin-2 and hence was serving as the output.

I couldn't, however, hear any problems with the output, and emrr's reply is probably all you need. If, however, anyone has had a chance to measure the effects of abusing one side of a dual opamp while using the other, I'd be interested to hear about the results!

Matthew

Hi,



      The G-SSL, for instance, does not like to be driven into an un-balanced load. You can lift pin 3 of the connecting XLR, but you will have to make up the 6dB loss.




    Kindest regards,


      ANdyP

You should have the advantage of knowing your gear, if you built it.

There are different flavors of active balanced outputs. Some will compensate for being hard single ended, some not.

If your outputs are just differential (two opposite polarity) but without feedback sensing for one of the two output lines being shorted, it wouldn't be a bad idea to float the shorted line. Transformer outputs generally tolerate one line being shorted, but if center-tapped with that center tap shorted, even a transformer output can be unhappy.

Know your gear, and adjust the wiring if needed.

JR

  I have heard my ACP88 get UGLY when driving an unbalanced load.  Check out this for the details:

  http://www.thatcorp.com/Line_Driver_Clipping_Behavior.shtml

It is so common for inserts to be unbalanced.  I have a British console at one place where the Insert Return load is the master fader, top and bottom.  They spared every expense on that baby!

My perfect equipment world would have all inputs mandatory balanced, and outputs whatever.  Aahh the bliss. . .

But as said before, if you don't hear anything dont sweat it.  The exceptions are lesser than the norm.
My short list of "hissy-fit" equipment are the Culture Vulture and the Retro Sta-Level.  For the price of the Vulture, they couldn't design it with balanced I/O?  And the Retro just wants to listen to the radio sometimes- different studios, balanced or unbalanced equipment situations.
Mike 

sodderboy said:

It is so common for inserts to be unbalanced.  I have a British console at one place where the Insert Return load is the master fader, top and bottom.  They spared every expense on that baby!

My perfect equipment world would have all inputs mandatory balanced, and outputs whatever.  Aahh the bliss. . .

But as said before, if you don't hear anything dont sweat it.  The exceptions are lesser than the norm.
My short list of "hissy-fit" equipment are the Culture Vulture and the Retro Sta-Level.  For the price of the Vulture, they couldn't design it with balanced I/O?  And the Retro just wants to listen to the radio sometimes- different studios, balanced or unbalanced equipment situations.
Mike   

Click to expand...

Having designed consoles with unbalanced inserts allow me to share.

Properly executed only the TRS jack itself is single legged. The signal being sent out to the insert jack is differential referenced to that jack sleeve so arbitrarily accurate wrt that sleeve node. Signal coming into the insert jack is likewise differential from that sleeve node. Proper 3 circuit wiring from the insert jack to a differential input nearby will maintain good signal integrity over modest distances. Transformer balanced, or active balanced outputs with cross connected load detecting feedback, can interface well with the insert being single ended at the sleeve node. Only the simple dual active output (or center tapped transformer) with no load sensing compensation, will be unhappy being single ended at the insert input, since one side is shorted to the sleeve. Even this can work, if the drivers are robust, while the sleeve leg on that send run can be corrupted by carrying the shorted audio line signal current. and crosstalk may be generated if it finds it's way back through a different ground. 

High end consoles offer balanced inserts but it is an expense not offered in many since properly done the cheaper TRS insert is more than adequate to cleanly interface with a nearby rack of gear. Proper wiring matters (the popular TRS to 2x TS "Y" cable is not the optimal solution, and know your output driver scheme.  If you need to send an insert point to a distant location (like say a plate reverb in a studio, but not "in" the studio) it may be worth adding some external driver if problems arise, but most console effects send-returns are balanced. 

JR

JohnRoberts said:

Only the simple dual active output (or center tapped transformer) with no load sensing compensation, will be unhappy being single ended at the insert input, since one side is shorted to the sleeve.
JR

Click to expand...

Center tapped output transformers in pro gear are pretty rare aren't they?  Yes, you CAN wire up an LA-2a that way.

IIRC I've seen one or two with the center tap floating. I am not a big fan or expert on legacy equipment.

I am just being thorough.

JR

John, please excuse the naivety of the question but in regards to "Proper wiring matters (the popular TRS to 2x TS "Y" cable is not the optimal solution..." as this is so prevalent, what do you recommend as the optimal solution?
Thanks,
JP

jpuhhuh said:

John, please excuse the naivety of the question but in regards to "Proper wiring matters (the popular TRS to 2x TS "Y" cable is not the optimal solution..." as this is so prevalent, what do you recommend as the optimal solution?
Thanks,
JP

Click to expand...

For the send side coming from the insert, use 2 conductor shielded wire connected to TRS or XLR. Tip/pin2 connects to send from insert. Ring/Pin 3 connects to sleeve at insert send, shield connects to sleeve/pin 1 only at input of receiving gear.

For the return side, this depends on the specific output topology of your gear. Again Tip/pin 2 from external gear connects to insert hot input. Sleeve/pin 1 from external gear connects to shield again only at the external gear end. If the Ring/pin 3 output is short circuit tolerant (load sensing cross connected feedback, or floating transformer output) connect it to the sleeve at the insert jack. If it is not short circuit tolerant (like simple active differential output or (the rare) center tapped transformer, leave it floating. This could be one conductor shielded if using one legged output, but not sure it's worth the trouble to source two different types of wire to DIY insert looms.

Again this requires knowing the output circuitry used in your equipment, but you can generally tell by how it behaves if it isn't happy.

Shorting a simple differential drive with a TS plug into a TRS jack, may work, since the current from the driver is being shunted right there at the TRS jack, but it isn't being kind to your gear.

As others have said if you are happy with the results you are getting, don't over think this. If you are getting problems, this is what to look for. 

JR

hello all correct me please if im wrong but i thought that the idea of the insert being unbalanced was to compensate for the make up gain of the inserted unit ie comps ect so basicly thesignal is lowered 6 db to accomadate the inserted

In my judgement it's purely a cost/panel real estate issue. The level could arbitrarily be set to any level but it is commonly set -6dB from active balanced outputs so clipping will occur at the same time and headroom is maintained for full path.

JR